v1.8.0

.gitignore

@@ -1,18 +1,6 @@
-*.gem
-*.rbc
-.bundle
-.config
-.yardoc
-Gemfile.lock
-InstalledFiles
-_yardoc
-coverage
-doc/
-lib/bundler/man
-pkg
-rdoc
-spec/reports
-test/tmp
-test/version_tmp
-tmp
-build_test_run
+/.yardoc/
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/build_test_run/

Gemfile.lock

@@ -0,0 +1,48 @@
+PATH
+  remote: .
+  specs:
+    rscons (1.8.0)
+      json (~> 1.0)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    diff-lcs (1.2.5)
+    docile (1.1.5)
+    json (1.8.1)
+    multi_json (1.10.1)
+    rake (10.3.2)
+    rdoc (4.1.2)
+      json (~> 1.4)
+    redcarpet (3.1.2)
+    rspec (3.0.0)
+      rspec-core (~> 3.0.0)
+      rspec-expectations (~> 3.0.0)
+      rspec-mocks (~> 3.0.0)
+    rspec-core (3.0.1)
+      rspec-support (~> 3.0.0)
+    rspec-expectations (3.0.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.0.0)
+    rspec-mocks (3.0.1)
+      rspec-support (~> 3.0.0)
+    rspec-support (3.0.0)
+    simplecov (0.8.2)
+      docile (~> 1.1.0)
+      multi_json
+      simplecov-html (~> 0.8.0)
+    simplecov-html (0.8.0)
+    yard (0.8.7.4)
+
+PLATFORMS
+  ruby
+  x86-mingw32
+
+DEPENDENCIES
+  rake
+  rdoc
+  redcarpet
+  rscons!
+  rspec
+  simplecov
+  yard

README.md

@@ -154,6 +154,31 @@ Rscons::Environment.new do |env|
 end
 ```
 
+### Example: Custom Builder Using Environment#add_builder()
+
+The `add_builder` method of the `Rscons::Environment` class optionally allows
+you to define and register a builder by providing a name and action block. This
+can be useful if the builder you are trying to define is easily expressed as a
+short ruby procedure. When `add_builder` is called in this manner a new builder
+will be registered with the environment with the given name. When this builder
+is used it will call the provided block in order to build the target.
+
+```ruby
+Rscons::Environment.new do |env|
+  env.add_builder(:JsonToYaml) do |target, sources, cache, env, vars|
+    unless cache.up_to_date?(target, :JsonToYaml, sources, env)
+      cache.mkdir_p(File.dirname(target))
+      File.open(target, 'w') do |f|
+        f.write(YAML.dump(JSON.load(IO.read(sources.first))))
+      end
+      cache.register_build(target, :JsonToYaml, sources, env)
+    end
+    target
+  end
+  env.JsonToYaml('foo.yml','foo.json')
+end
+```
+
 ### Example: Using different compilation flags for some sources
 
 ```ruby
@@ -173,6 +198,9 @@ Each build hook block will be invoked for every build operation, so the block
 should test the target or sources if its action should only apply to some
 subset of build targets or source files.
 
+Build hooks can alter construction variable values for a particular build
+operation. Build hooks can also register new build targets.
+
 The `build_op` parameter to the build hook block is a Hash describing the
 build operation with the following keys:
 * `:builder` - `Builder` instance in use
@@ -207,6 +235,7 @@ end
 
 Rscons ships with a number of builders:
 
+* Command, which executes a user-defined command to produce the target
 * CFile, which builds a C or C++ source file from a lex or yacc input file
 * Disassemble, which disassembles an object file to a disassembly listing
 * Library, which collects object files into a static library archive file
@@ -217,6 +246,18 @@ Rscons ships with a number of builders:
 If you want to create an Environment that does not contain any builders,
 you can use the `exclude_builders` key to the Environment constructor.
 
+#### Command
+
+```ruby
+env.Command(target, sources, 'CMD' => command)
+# Example
+env.Command("docs.html", "docs.md",
+    CMD => ['pandoc', '-fmarkdown', '-thtml', '-o${_TARGET}', '${_SOURCES}'])
+```
+
+The command builder executes a user-defined command in order to produce the
+desired target file based on the provided source files.
+
 #### CFile
 
 ```ruby
@@ -317,6 +358,19 @@ cloned_env["CPPPATH"] << "three"
 
 `base_env["CPPPATH"]` will not include "three".
 
+#### Build Hooks
+
+Environments can have build hooks which are added with `env.add_build_hook()`.
+Build hooks are invoked immediately before a builder executes.
+Build hooks can modify the construction variables in use for the build
+operation.
+They can also register new build targets.
+
+Environments can also have post-build hooks added with `env.add_post_build_hook()`.
+Post-build hooks are only invoked if the build operation was a success.
+Post-build hooks can invoke commands using the newly-built files, or register
+new build targets.
+
 ### Construction Variable Naming
 
 * uppercase strings - the default construction variables that Rscons uses
@@ -329,6 +383,43 @@ http://rubydoc.info/github/holtrop/rscons/frames.
 
 ## Release Notes
 
+### v1.8.0
+
+- new Command builder to execute arbitrary user commands
+- new SimpleBuilder class
+  - create new builders quickly by passing a block to Environment#add_builder
+- improved YARD documentation
+- add Environment#dump to debug Environment construction variables
+
+### v1.7.0
+
+- allow build hooks to register new build targets
+- add post-build hooks (register with Environment#add_post_build_hook)
+- clear all build targets after processing an Environment
+- allow trailing slashes in arguments to Environment#build_dir
+
+### v1.6.1
+
+- add DEPFILESUFFIX construction variable to override dependency file suffix
+- fix Environment#depends to expand its arguments for construction variables
+
+### v1.6.0
+
+- support lambdas as construction variable values
+
+### v1.5.0
+
+- add "json" as a runtime dependency
+- update construction variables to match SCons more closely
+  - add CPPDEFPREFIX, INCPREFIX, CPPDEFINES, CCFLAGS, LIBDIRPREFIX, and LIBLINKPREFIX
+- add Environment#shell
+- add Environment#parse_flags, #parse_flags!, #merge_flags
+- unbuffer $stdout by default
+- add PROGSUFFIX construction variable (defaults to .exe on MinGW/Cygwin)
+- add Rscons::BuildTarget and Builder#create_build_target
+- update specs to RSpec 3.x and fix to run on MinGW/Cygwin/Linux
+- add YARD documentation to get to 100% coverage
+
 ### v1.4.3
 
 - fix builders properly using construction variable overrides

Rakefile.rb

@@ -8,6 +8,10 @@ end
 require "bundler/gem_tasks"
 require "rspec/core/rake_task"
 require "yard"
+require "rake/clean"
+
+CLEAN.include %w[build_test_run .yardoc doc coverage]
+CLOBBER.include %w[pkg]
 
 RSpec::Core::RakeTask.new(:spec)
 
@@ -16,11 +20,3 @@ YARD::Rake::YardocTask.new do |yard|
 end
 
 task :default => :spec
-
-task :clean do
-  FileUtils.rm_rf(["build_test_run", "doc", "coverage"])
-end
-
-task :clobber => :clean do
-  FileUtils.rm_rf(["pkg"])
-end

build_tests/json_to_yaml/foo.json

@@ -0,0 +1 @@
+{ "key": "value" }

lib/rscons.rb

@@ -6,18 +6,21 @@ require_relative "rscons/varset"
 require_relative "rscons/version"
 
 # default builders
+require_relative "rscons/builders/command"
 require_relative "rscons/builders/cfile"
 require_relative "rscons/builders/disassemble"
 require_relative "rscons/builders/library"
 require_relative "rscons/builders/object"
 require_relative "rscons/builders/preprocess"
 require_relative "rscons/builders/program"
+require_relative "rscons/builders/simple_builder"
 
 # Namespace module for rscons classes
 module Rscons
   # Names of the default builders which will be added to all newly created
   # {Environment} objects.
   DEFAULT_BUILDERS = [
+    :Command,
     :CFile,
     :Disassemble,
     :Library,
@@ -30,6 +33,8 @@ module Rscons
   class BuildError < RuntimeError; end
 
   # Remove all generated files.
+  #
+  # @return [void]
   def self.clean
     cache = Cache.instance
     # remove all built files
@@ -118,6 +123,8 @@ module Rscons
   # Set the command executer array.
   #
   # @param val [Array<String>] Command used to execute commands.
+  #
+  # @return [Array<String>] Command used to execute commands.
   def self.command_executer=(val)
     @@command_executer = val
   end

lib/rscons/builder.rb

@@ -9,6 +9,8 @@ module Rscons
     # Return the name of the builder.
     #
     # If not overridden this defaults to the last component of the class name.
+    #
+    # @return [String] The name of the builder.
     def name
       self.class.name.split(":").last
     end
@@ -44,7 +46,7 @@ module Rscons
     # file name from a given source file name.
     #
     # @param target [String] The target file name.
-    # @param source [String, Array] The source file name(s).
+    # @param source [String] The source file name.
     # @param env [Environment] The Environment.
     #
     # @return [Boolean]
@@ -54,6 +56,20 @@ module Rscons
       false
     end
 
+    # Run the builder to produce a build target.
+    #
+    # @param target [String] Target file name.
+    # @param sources [Array<String>] Source file name(s).
+    # @param cache [Cache] The Cache object.
+    # @param env [Environment] The Environment executing the builder.
+    # @param vars [Hash,VarSet] Extra construction variables.
+    #
+    # @return [String,false]
+    #   Name of the target file on success or false on failure.
+    def run(target, sources, cache, env, vars)
+      raise "This method must be overridden in a subclass"
+    end
+
     # Check if the cache is up to date for the target and if not execute the
     # build command.
     #

lib/rscons/builders/command.rb

@@ -0,0 +1,32 @@
+module Rscons
+  module Builders
+    # Execute a command that will produce the given target based on the given
+    # sources.
+    #
+    # @since 1.8.0
+    #
+    # Example:
+    #   env.Command("docs.html", "docs.md",
+    #               CMD => %w[pandoc -fmarkdown -thtml -o${_TARGET} ${_SOURCES}])
+    class Command < Builder
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
+      def run(target, sources, cache, env, vars)
+        vars = vars.merge({
+          "_TARGET" => target,
+          "_SOURCES" => sources,
+        })
+        command = env.build_command("${CMD}", vars)
+        standard_build("CMD #{target}", target, command, sources, env, cache)
+      end
+    end
+  end
+end

lib/rscons/builders/object.rb

@@ -19,6 +19,7 @@ module Rscons
       def default_variables(env)
         {
           'OBJSUFFIX' => '.o',
+          'DEPFILESUFFIX' => '.mf',
 
           'CPPDEFPREFIX' => '-D',
           'INCPREFIX' => '-I',
@@ -61,7 +62,7 @@ module Rscons
       # file name from a given source file name.
       #
       # @param target [String] The target file name.
-      # @param source [String, Array] The source file name(s).
+      # @param source [String] The source file name.
       # @param env [Environment] The Environment.
       #
       # @return [Boolean]
@@ -87,7 +88,7 @@ module Rscons
         vars = vars.merge({
           '_TARGET' => target,
           '_SOURCES' => sources,
-          '_DEPFILE' => Rscons.set_suffix(target, '.mf'),
+          '_DEPFILE' => Rscons.set_suffix(target, env.expand_varref("${DEPFILESUFFIX}", vars)),
         })
         com_prefix = KNOWN_SUFFIXES.find do |compiler, suffix_var|
           sources.first.end_with?(*env.expand_varref("${#{suffix_var}}"))

lib/rscons/builders/simple_builder.rb

@@ -0,0 +1,39 @@
+module Rscons
+  module Builders
+    # A Generic builder class whose name and operation is defined at
+    # instantiation.
+    #
+    # @since 1.8.0
+    class SimpleBuilder < Builder
+      # @return [String] The name of this builder.
+      attr_reader :name
+
+      # Create a new builder with the given name and action.
+      #
+      # @param name  [String,Symbol] The name of the builder when registered.
+      # @param block [Block]
+      #   The action to perform when the builder is processed. The provided
+      #   block must return the target file on success or false on failure.
+      #   The provided block should have the same signature as {Builder#run}.
+      def initialize(name, &block)
+        @name  = name.to_s
+        @block = block
+      end
+
+      # Run the builder to produce a build target.
+      #
+      # @param target [String] Target file name.
+      # @param sources [Array<String>] Source file name(s).
+      # @param cache [Cache] The Cache object.
+      # @param env [Environment] The Environment executing the builder.
+      # @param vars [Hash,VarSet] Extra construction variables.
+      #
+      # @return [String,false]
+      #   Name of the target file on success or false on failure.
+      def run(target, sources, cache, env, vars)
+        @block.call(target, sources, cache, env, vars)
+      end
+    end
+  end
+end
+

lib/rscons/cache.rb

@@ -63,17 +63,23 @@ module Rscons
     end
 
     # Remove the cache file.
+    #
+    # @return [void]
     def clear
       FileUtils.rm_f(CACHE_FILE)
       initialize!
     end
 
     # Clear the cached file checksums.
+    #
+    # @return [void]
     def clear_checksum_cache!
       @lookup_checksums = {}
     end
 
     # Write the cache to disk to be loaded next time.
+    #
+    # @return [void]
     def write
       if @dirty || (@cache["version"] != VERSION)
         @cache["version"] = VERSION
@@ -86,9 +92,14 @@ module Rscons
 
     # Check if target(s) are up to date.
     #
-    # @param targets [String, Array] The name(s) of the target file(s).
-    # @param command [String, Array] The command used to build the target.
-    # @param deps [Array] List of the target's dependency files.
+    # @param targets [String, Array<String>] The name(s) of the target file(s).
+    # @param command [String, Array, Hash]
+    #   The command used to build the target. The command parameter can
+    #   actually be a String, Array, or Hash and could contain information
+    #   other than just the actual command used to build the target. For the
+    #   purposes of the Cache, any difference in the command argument will
+    #   trigger a rebuild.
+    # @param deps [Array<String>] List of the target's dependency files.
     # @param env [Environment] The Rscons::Environment.
     # @param options [Hash] Optional options.
     # @option options [Boolean] :strict_deps
@@ -148,9 +159,14 @@ module Rscons
 
     # Store cache information about target(s) built by a builder.
     #
-    # @param targets [String, Array] The name of the target(s) built.
-    # @param command [String, Array] The command used to build the target.
-    # @param deps [Array] List of dependencies for the target.
+    # @param targets [String, Array<String>] The name of the target(s) built.
+    # @param command [String, Array, Hash]
+    #   The command used to build the target. The command parameter can
+    #   actually be a String, Array, or Hash and could contain information
+    #   other than just the actual command used to build the target. For the
+    #   purposes of the Cache, any difference in the command argument will
+    #   trigger a rebuild.
+    # @param deps [Array<String>] List of dependencies for the target.
     # @param env [Environment] The {Rscons::Environment}.
     #
     # @return [void]

lib/rscons/environment.rb

@@ -7,10 +7,10 @@ module Rscons
   # contains a collection of construction variables, options, builders, and
   # rules for building targets.
   class Environment
-    # @return [Hash] Set of \{"builder_name" => builder_object} pairs.
+    # @return [Hash] Set of !{"builder_name" => builder_object} pairs.
     attr_reader :builders
 
-    # :command, :short, or :off
+    # @return [Symbol] :command, :short, or :off
     attr_accessor :echo
 
     # @return [String, nil] The build root.
@@ -42,7 +42,7 @@ module Rscons
       @user_deps = {}
       @builders = {}
       @build_dirs = []
-      @build_hooks = []
+      @build_hooks = {pre: [], post: []}
       unless options[:exclude_builders]
         DEFAULT_BUILDERS.each do |builder_class_name|
           builder_class = Builders.const_get(builder_class_name)
@@ -79,7 +79,7 @@ module Rscons
     #
     # Any options that #initialize receives can also be specified here.
     #
-    # @return a new {Environment} object.
+    # @return [Environment] The newly created {Environment} object.
     def clone(options = {})
       clone = options[:clone] || Set[:variables, :builders]
       clone = Set[:variables, :builders, :build_root, :build_dirs, :build_hooks] if clone == :all
@@ -103,9 +103,12 @@ module Rscons
         end
       end
       if clone.include?(:build_hooks)
-        @build_hooks.each do |build_hook_block|
+        @build_hooks[:pre].each do |build_hook_block|
           env.add_build_hook(&build_hook_block)
         end
+        @build_hooks[:post].each do |build_hook_block|
+          env.add_post_build_hook(&build_hook_block)
+        end
       end
 
       if block_given?
@@ -117,10 +120,32 @@ module Rscons
 
     # Add a {Builder} object to the Environment.
     #
-    # @param builder [Builder] The {Builder} object to add.
+    # @overload add_builder(builder)
+    #
+    #   Add the given builder to the Environment.
+    #
+    #   @param builder [Builder] An instance of the builder to register.
+    #
+    # @overload add_builder(builder,&action)
+    #
+    #   Create a new {Builders::SimpleBuilder} instance and add it to the
+    #   environment.
+    #
+    #   @since 1.8.0
+    #
+    #   @param builder [String,Symbol]
+    #     The name of the builder to add.
+    #
+    #   @param action [Block]
+    #     A block that will be called when the builder is executed to generate
+    #     a target file. The provided block should have the same prototype as
+    #     {Rscons::Builder#run}.
     #
     # @return [void]
-    def add_builder(builder)
+    def add_builder(builder, &action)
+      if not builder.is_a? Rscons::Builder
+        builder = Rscons::Builders::SimpleBuilder.new(builder, &action)
+      end
       @builders[builder.name] = builder
       var_defs = builder.default_variables(self)
       if var_defs
@@ -132,6 +157,12 @@ module Rscons
 
     # Add a build hook to the Environment.
     #
+    # Build hooks are Ruby blocks which are invoked immediately before a
+    # build operation takes place. Build hooks have an opportunity to modify
+    # the construction variables in use for the build operation based on the
+    # builder in use, target file name, or sources. Build hooks can also
+    # register new build targets.
+    #
     # @yield [build_op]
     #   Invoke the given block with the current build operation.
     # @yieldparam build_op [Hash]
@@ -144,19 +175,50 @@ module Rscons
     #
     # @return [void]
     def add_build_hook(&block)
-      @build_hooks << block
+      @build_hooks[:pre] << block
+    end
+
+    # Add a post build hook to the Environment.
+    #
+    # Post-build hooks are Ruby blocks which are invoked immediately after a
+    # build operation takes place. Post-build hooks are only invoked if the
+    # build operation succeeded. Post-build hooks can register new build
+    # targets.
+    #
+    # @since 1.7.0
+    #
+    # @yield [build_op]
+    #   Invoke the given block with the current build operation.
+    # @yieldparam build_op [Hash]
+    #   Hash with keys:
+    #   - :builder - The builder object in use.
+    #   - :target - Target file name.
+    #   - :sources - List of source file(s).
+    #   - :vars - Set of construction variable values in use.
+    #   - :env - The Environment invoking the builder.
+    #
+    # @return [void]
+    def add_post_build_hook(&block)
+      @build_hooks[:post] << block
     end
 
     # Specify a build directory for this Environment.
     #
     # Source files from src_dir will produce object files under obj_dir.
     #
-    # @param src_dir [String] Path to the source directory.
-    # @param obj_dir [String] Path to the object directory.
+    # @param src_dir [String, Regexp]
+    #   Path to the source directory. If a Regexp is given, it will be matched
+    #   to source file names.
+    # @param obj_dir [String]
+    #   Path to the object directory. If a Regexp is given as src_dir, then
+    #   obj_dir can contain backreferences to groups matched from the source
+    #   file name.
     #
     # @return [void]
     def build_dir(src_dir, obj_dir)
-      src_dir = src_dir.gsub('\\', '/') if src_dir.is_a?(String)
+      if src_dir.is_a?(String)
+        src_dir = src_dir.gsub("\\", "/").sub(%r{/*$}, "")
+      end
       @build_dirs << [src_dir, obj_dir]
     end
 
@@ -188,25 +250,27 @@ module Rscons
       build_fname
     end
 
-    # Access a construction variable or environment option.
+    # Get a construction variable's value.
     #
     # @see VarSet#[]
     def [](*args)
       @varset.send(:[], *args)
     end
 
-    # Set a construction variable or environment option.
+    # Set a construction variable's value.
     #
     # @see VarSet#[]=
     def []=(*args)
       @varset.send(:[]=, *args)
     end
 
-    # Add a set of construction variables or environment options.
+    # Add a set of construction variables to the Environment.
     #
-    # @see VarSet#append
-    def append(*args)
-      @varset.append(*args)
+    # @param values [VarSet, Hash] New set of variables.
+    #
+    # @return [void]
+    def append(values)
+      @varset.append(values)
     end
 
     # Build all build targets specified in the Environment.
@@ -216,23 +280,25 @@ module Rscons
     #
     # @return [void]
     def process
-      unless @targets.empty?
-        expand_paths!
+      expand_paths!
+      while @targets.size > 0
+        targets = @targets
+        @targets = {}
         cache = Cache.instance
         cache.clear_checksum_cache!
         targets_processed = {}
         process_target = proc do |target|
           targets_processed[target] ||= begin
-            @targets[target][:sources].each do |src|
-              if @targets.include?(src) and not targets_processed.include?(src)
+            targets[target][:sources].each do |src|
+              if targets.include?(src) and not targets_processed.include?(src)
                 process_target.call(src)
               end
             end
-            result = run_builder(@targets[target][:builder],
+            result = run_builder(targets[target][:builder],
                                  target,
-                                 @targets[target][:sources],
+                                 targets[target][:sources],
                                  cache,
-                                 @targets[target][:vars] || {})
+                                 targets[target][:vars] || {})
             unless result
               raise BuildError.new("Failed to build #{target}")
             end
@@ -240,7 +306,7 @@ module Rscons
           end
         end
         begin
-          @targets.each do |target, target_params|
+          targets.each do |target, target_params|
             process_target.call(target)
           end
         ensure
@@ -250,6 +316,8 @@ module Rscons
     end
 
     # Clear all targets registered for the Environment.
+    #
+    # @return [void]
     def clear_targets
       @targets = {}
     end
@@ -263,11 +331,13 @@ module Rscons
     #
     # @return [Array, String] Expansion of the variable reference.
     def expand_varref(varref, extra_vars = nil)
-      if extra_vars.nil?
-        @varset
-      else
-        @varset.merge(extra_vars)
-      end.expand_varref(varref)
+      vars = if extra_vars.nil?
+               @varset
+             else
+               @varset.merge(extra_vars)
+             end
+      lambda_args = [env: self, vars: vars]
+      vars.expand_varref(varref, lambda_args)
     end
     alias_method :build_command, :expand_varref
 
@@ -349,7 +419,8 @@ module Rscons
     #
     # @return [void]
     def depends(target, *user_deps)
-      target = target.to_s
+      target = expand_varref(target.to_s)
+      user_deps = user_deps.map {|ud| expand_varref(ud)}
       @user_deps[target] ||= []
       @user_deps[target] = (@user_deps[target] + user_deps).uniq
     end
@@ -370,8 +441,9 @@ module Rscons
     #
     # This method is used internally by Rscons builders.
     #
-    # @param sources [Array] List of source files to build.
-    # @param suffixes [Array] List of suffixes to try to convert source files into.
+    # @param sources [Array<String>] List of source files to build.
+    # @param suffixes [Array<String>]
+    #   List of suffixes to try to convert source files into.
     # @param cache [Cache] The Cache.
     # @param vars [Hash] Extra variables to pass to the builder.
     #
@@ -400,24 +472,29 @@ module Rscons
     #
     # @param builder [Builder] The Builder to use.
     # @param target [String] The target output file.
-    # @param sources [Array] List of source files.
+    # @param sources [Array<String>] List of source files.
     # @param cache [Cache] The Cache.
     # @param vars [Hash] Extra variables to pass to the builder.
     #
     # @return [String,false] Return value from the {Builder}'s +run+ method.
     def run_builder(builder, target, sources, cache, vars)
       vars = @varset.merge(vars)
-      @build_hooks.each do |build_hook_block|
-        build_operation = {
-          builder: builder,
-          target: target,
-          sources: sources,
-          vars: vars,
-          env: self,
-        }
-        build_hook_block.call(build_operation)
+      call_build_hooks = lambda do |sec|
+        @build_hooks[sec].each do |build_hook_block|
+          build_operation = {
+            builder: builder,
+            target: target,
+            sources: sources,
+            vars: vars,
+            env: self,
+          }
+          build_hook_block.call(build_operation)
+        end
       end
-      builder.run(target, sources, cache, self, vars)
+      call_build_hooks[:pre]
+      rv = builder.run(target, sources, cache, self, vars)
+      call_build_hooks[:post] if rv
+      rv
     end
 
     # Expand a path to be relative to the Environment's build root.
@@ -461,10 +538,10 @@ module Rscons
     # Parse command-line flags for compilation/linking options into separate
     # construction variables.
     #
-    # The parsed construction variables are returned in a Hash instead of
-    # merging them directly to the Environment. They can be merged with
-    # {#merge_flags}. The {#parse_flags!} version immediately merges the parsed
-    # flags as well.
+    # For {#parse_flags}, the parsed construction variables are returned in a
+    # Hash instead of merging them directly to the Environment. They can be
+    # merged with {#merge_flags}. The {#parse_flags!} version immediately
+    # merges the parsed flags as well.
     #
     # Example:
     #   # Import FreeType build options
@@ -583,6 +660,13 @@ module Rscons
       end
     end
 
+    # Print the Environment's construction variables for debugging.
+    def dump
+      @varset.to_h.sort.each do |var, val|
+        puts "#{var} => #{val.inspect}"
+      end
+    end
+
     private
 
     # Expand target and source paths before invoking builders.

lib/rscons/varset.rb

@@ -58,7 +58,7 @@ module Rscons
     #
     # @param values [VarSet, Hash] New set of variables.
     #
-    # @return [self]
+    # @return [VarSet] Returns self.
     def append(values)
       coa!
       if values.is_a?(VarSet)
@@ -83,32 +83,61 @@ module Rscons
     end
     alias_method :clone, :merge
 
-    # Replace "$\{var}" variable references in varref with the expanded
+    # Replace "$!{var}" variable references in varref with the expanded
     # variables' values, recursively.
     #
-    # @param varref [String, Array] Value containing references to variables.
+    # @param varref [nil, String, Array, Proc]
+    #   Value containing references to variables.
+    # @param lambda_args [Array]
+    #   Arguments to pass to any lambda variable values to be expanded.
     #
-    # @return [String, Array]
-    #   Expanded value with "$\{var}" variable references replaced.
-    def expand_varref(varref)
-      if varref.is_a?(Array)
-        varref.map do |ent|
-          expand_varref(ent)
-        end.flatten
-      else
+    # @return [nil, String, Array]
+    #   Expanded value with "$!{var}" variable references replaced.
+    def expand_varref(varref, lambda_args)
+      if varref.is_a?(String)
         if varref =~ /^(.*)\$\{([^}]+)\}(.*)$/
           prefix, varname, suffix = $1, $2, $3
-          varval = expand_varref(self[varname])
+          varval = expand_varref(self[varname], lambda_args)
           if varval.is_a?(String) or varval.nil?
-            expand_varref("#{prefix}#{varval}#{suffix}")
+            expand_varref("#{prefix}#{varval}#{suffix}", lambda_args)
           elsif varval.is_a?(Array)
-            varval.map {|vv| expand_varref("#{prefix}#{vv}#{suffix}")}.flatten
+            varval.map {|vv| expand_varref("#{prefix}#{vv}#{suffix}", lambda_args)}.flatten
           else
             raise "I do not know how to expand a variable reference to a #{varval.class.name} (from #{varname.inspect} => #{self[varname].inspect})"
           end
         else
           varref
         end
+      elsif varref.is_a?(Array)
+        varref.map do |ent|
+          expand_varref(ent, lambda_args)
+        end.flatten
+      elsif varref.is_a?(Proc)
+        expand_varref(varref[*lambda_args], lambda_args)
+      elsif varref.nil?
+        nil
+      else
+        raise "Unknown varref type: #{varref.class} (#{varref.inspect})"
+      end
+    end
+
+    # Return a Hash containing all variables in the VarSet.
+    #
+    # @since 1.8.0
+    #
+    # This method is not terribly efficient. It is intended to be used only by
+    # debugging code to dump out a VarSet's variables.
+    #
+    # @return [Hash] All variables in the VarSet.
+    def to_h
+      result = deep_dup(@my_vars)
+      @coa_vars.reduce(result) do |result, coa_vars|
+        coa_vars.each_pair do |key, value|
+          unless result.include?(key)
+            result[key] = deep_dup(value)
+          end
+        end
+        result
       end
     end
 

lib/rscons/version.rb

@@ -1,4 +1,4 @@
 module Rscons
   # gem version
-  VERSION = "1.5.0"
+  VERSION = "1.8.0"
 end

rscons.gemspec

@@ -24,5 +24,6 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency "rake"
   gem.add_development_dependency "simplecov"
   gem.add_development_dependency "yard"
+  gem.add_development_dependency "rdoc"
   gem.add_development_dependency "redcarpet"
 end

spec/build_tests_spec.rb

@@ -10,6 +10,7 @@ class Dir
 end
 
 describe Rscons do
+
   BUILD_TEST_RUN_DIR = "build_test_run"
 
   def rm_rf(dir)
@@ -120,34 +121,43 @@ describe Rscons do
 
   it 'rebuilds a C module when a header it depends on changes' do
     test_dir('header')
-    env = Rscons::Environment.new do |env|
-      env.Program('header', Dir['*.c'])
+    make_env = lambda do
+      Rscons::Environment.new do |env|
+        env.Program('header', Dir['*.c'])
+      end
     end
+    make_env[]
     expect(`./header`).to eq "The value is 2\n"
     file_sub('header.h') {|line| line.sub(/2/, '5')}
-    env.process
+    make_env[]
     expect(`./header`).to eq "The value is 5\n"
   end
 
   it 'does not rebuild a C module when its dependencies have not changed' do
     test_dir('header')
-    env = Rscons::Environment.new do |env|
-      env.Program('header', Dir['*.c'])
+    make_env = lambda do
+      Rscons::Environment.new do |env|
+        env.Program('header', Dir['*.c'])
+      end
     end
+    env = make_env[]
     expect(`./header`).to eq "The value is 2\n"
     expect(lines).to eq [
       'CC header.o',
       "LD header#{env["PROGSUFFIX"]}",
     ]
-    env.process
+    make_env[]
     expect(lines).to eq []
   end
 
   it "does not rebuild a C module when only the file's timestamp has changed" do
     test_dir('header')
-    env = Rscons::Environment.new do |env|
-      env.Program('header', Dir['*.c'])
+    make_env = lambda do
+      Rscons::Environment.new do |env|
+        env.Program('header', Dir['*.c'])
+      end
     end
+    env = make_env[]
     expect(`./header`).to eq "The value is 2\n"
     expect(lines).to eq [
       'CC header.o',
@@ -155,7 +165,7 @@ describe Rscons do
     ]
     sleep 0.05
     file_sub('header.c') {|line| line}
-    env.process
+    make_env[]
     expect(lines).to eq []
   end
 
@@ -187,6 +197,19 @@ describe Rscons do
     expect(File.exists?('build_two/two.o')).to be_truthy
   end
 
+  it "supports trailing slashes at the end of build_dir sources and destinations" do
+    test_dir("build_dir")
+    Rscons::Environment.new do |env|
+      env.append("CPPPATH" => Dir["src/**/*/"])
+      env.build_dir("src/one/", "build_one/")
+      env.build_dir("src/two", "build_two")
+      env.Program("build_dir", Dir["src/**/*.c"])
+    end
+    expect(`./build_dir`).to eq "Hello from two()\n"
+    expect(File.exists?("build_one/one.o")).to be_truthy
+    expect(File.exists?("build_two/two.o")).to be_truthy
+  end
+
   it 'uses build directories before build root' do
     test_dir('build_dir')
     env = Rscons::Environment.new do |env|
@@ -226,6 +249,27 @@ describe Rscons do
     ]
   end
 
+  it 'supports simple builders' do
+    test_dir('json_to_yaml')
+    Rscons::Environment.new do |env|
+      require 'json'
+      require 'yaml'
+      env.add_builder(:JsonToYaml) do |target, sources, cache, env, vars|
+        unless cache.up_to_date?(target, :JsonToYaml, sources, env)
+          cache.mkdir_p(File.dirname(target))
+          File.open(target, 'w') do |f|
+            f.write(YAML.dump(JSON.load(IO.read(sources.first))))
+          end
+          cache.register_build(target, :JsonToYaml, sources, env)
+        end
+        target
+      end
+      env.JsonToYaml('foo.yml','foo.json')
+    end
+    expect(File.exists?('foo.yml')).to be_truthy
+    expect(IO.read('foo.yml')).to eq("---\nkey: value\n")
+  end
+
   it 'cleans built files' do
     test_dir('build_dir')
     Rscons::Environment.new do |env|
@@ -303,11 +347,14 @@ EOF
       end
     end
 
-    env = Rscons::Environment.new do |env|
-      env.add_builder(CHGen.new)
-      env.CHGen("inc.c", ["program.c"])
-      env.Program("program", Dir["*.c"] + ["inc.c"])
+    make_env = lambda do
+      Rscons::Environment.new do |env|
+        env.add_builder(CHGen.new)
+        env.CHGen("inc.c", ["program.c"])
+        env.Program("program", %w[program.c inc.c])
+      end
     end
+    env = make_env[]
 
     expect(lines).to eq ["CHGen inc.c", "CC program.o", "CC inc.o", "LD program#{env["PROGSUFFIX"]}"]
     expect(File.exists?("inc.c")).to be_truthy
@@ -315,7 +362,7 @@ EOF
     expect(`./program`).to eq "The value is 42\n"
 
     File.open("inc.c", "w") {|fh| fh.puts "int THE_VALUE = 33;"}
-    env.process
+    make_env[]
     expect(lines).to eq ["CHGen inc.c"]
     expect(`./program`).to eq "The value is 42\n"
   end
@@ -347,12 +394,16 @@ EOF
   it 'allows cloning all attributes of an Environment object' do
     test_dir('clone_env')
 
+    built_targets = []
     env1 = Rscons::Environment.new(echo: :command) do |env|
       env.build_dir('src', 'build')
       env['CFLAGS'] = '-O2'
       env.add_build_hook do |build_op|
         build_op[:vars]['CPPFLAGS'] = '-DSTRING="Hello"'
       end
+      env.add_post_build_hook do |build_op|
+        built_targets << build_op[:target]
+      end
       env.Program('program', Dir['src/*.c'])
     end
 
@@ -365,6 +416,12 @@ EOF
       %Q{gcc -o program#{env1["PROGSUFFIX"]} build/program.o},
       %Q{gcc -o program2#{env2["PROGSUFFIX"]} build/program.o},
     ]
+    expect(built_targets).to eq([
+      "build/program.o",
+      "program#{env1['PROGSUFFIX']}",
+      "build/program.o",
+      "program2#{env1['PROGSUFFIX']}",
+    ])
   end
 
   it 'builds a C++ program with one source file' do
@@ -543,4 +600,136 @@ EOF
     expect(File.exists?('inc.h')).to be_truthy
     expect(`./program`).to eq "The value is 678\n"
   end
+
+  it "supports lambdas as construction variable values" do
+    env = Rscons::Environment.new do |env|
+      env["prefix"] = "-H"
+      env["suffix"] = "xyz"
+      env[:cfg] = {val: 44}
+      env["computed"] = lambda do |args|
+        "#{args[:env]['prefix']}#{args[:env][:cfg][:val]}#{args[:env]['suffix']}"
+      end
+      env["lambda_recurse"] = lambda do |args|
+        "${prefix}ello"
+      end
+    end
+    e2 = env.clone
+    e2[:cfg][:val] = 38
+    expect(env.expand_varref("${computed}")).to eq("-H44xyz")
+    expect(e2.expand_varref("${computed}")).to eq("-H38xyz")
+    expect(env.expand_varref("${lambda_recurse}")).to eq("-Hello")
+  end
+
+  it "supports registering build targets from within a build hook" do
+    test_dir("simple")
+    Rscons::Environment.new do |env|
+      env.Program("simple", Dir["*.c"])
+      env.add_build_hook do |build_op|
+        if build_op[:target].end_with?(".o")
+          env.Disassemble("#{build_op[:target]}.txt", build_op[:target])
+        end
+      end
+    end
+    expect(File.exists?("simple.o")).to be_truthy
+    expect(File.exists?("simple.o.txt")).to be_truthy
+    expect(`./simple`).to eq "This is a simple C program\n"
+  end
+
+  it "supports post-build hooks" do
+    test_dir("simple")
+    built_targets = []
+    env = Rscons::Environment.new do |env|
+      env.Program("simple", Dir["*.c"])
+      env.add_post_build_hook do |build_op|
+        built_targets << build_op[:target]
+        expect(File.exists?(build_op[:target])).to be_truthy
+      end
+    end
+    expect(File.exists?("simple.o")).to be_truthy
+    expect(`./simple`).to eq "This is a simple C program\n"
+    expect(built_targets).to eq ["simple.o", "simple#{env["PROGSUFFIX"]}"]
+  end
+
+  it "supports multiple values for CXXSUFFIX" do
+    test_dir("simple_cc")
+    File.open("other.cccc", "w") {|fh| fh.puts}
+    Rscons::Environment.new do |env|
+      env["CXXSUFFIX"] = %w[.cccc .cc]
+      env["CXXFLAGS"] += %w[-x c++]
+      env.Program("simple", Dir["*.cc"] + ["other.cccc"])
+    end
+    expect(File.exists?("simple.o")).to be_truthy
+    expect(File.exists?("other.o")).to be_truthy
+    expect(`./simple`).to eq "This is a simple C++ program\n"
+  end
+
+  it "supports multiple values for CSUFFIX" do
+    test_dir("build_dir")
+    FileUtils.mv("src/one/one.c", "src/one/one.yargh")
+    Rscons::Environment.new do |env|
+      env["CSUFFIX"] = %w[.yargh .c]
+      env["CFLAGS"] += %w[-x c]
+      env["CPPPATH"] += Dir["src/**/"]
+      env.Program("build_dir", Dir["src/**/*.{c,yargh}"])
+    end
+    expect(File.exists?("src/one/one.o")).to be_truthy
+    expect(File.exists?("src/two/two.o")).to be_truthy
+    expect(`./build_dir`).to eq "Hello from two()\n"
+  end
+
+  it "supports multiple values for OBJSUFFIX" do
+    test_dir("two_sources")
+    env = Rscons::Environment.new() do |env|
+      env["OBJSUFFIX"] = %w[.oooo .ooo]
+      env.Object("one.oooo", "one.c", "CPPFLAGS" => ["-DONE"])
+      env.Object("two.ooo", "two.c")
+      env.Program("two_sources", %w[one.oooo two.ooo])
+    end
+    expect(File.exists?("two_sources#{env["PROGSUFFIX"]}")).to be_truthy
+    expect(`./two_sources`).to eq "This is a C program with two sources.\n"
+  end
+
+  it "supports multiple values for LIBSUFFIX" do
+    test_dir("two_sources")
+    env = Rscons::Environment.new() do |env|
+      env["LIBSUFFIX"] = %w[.aaaa .aaa]
+      env.Library("one.aaaa", "one.c", "CPPFLAGS" => ["-DONE"])
+      env.Library("two.aaa", "two.c")
+      env.Program("two_sources", %w[one.aaaa two.aaa])
+    end
+    expect(File.exists?("two_sources#{env["PROGSUFFIX"]}")).to be_truthy
+    expect(`./two_sources`).to eq "This is a C program with two sources.\n"
+  end
+
+  it "supports multiple values for ASSUFFIX" do
+    test_dir("two_sources")
+    env = Rscons::Environment.new() do |env|
+      env["ASSUFFIX"] = %w[.ssss .sss]
+      env["CFLAGS"] += %w[-S]
+      env.Object("one.ssss", "one.c", "CPPFLAGS" => ["-DONE"])
+      env.Object("two.sss", "two.c")
+      env.Program("two_sources", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler])
+    end
+    expect(lines).to eq([
+      "CC one.ssss",
+      "CC two.sss",
+      "AS one.o",
+      "AS two.o",
+      "LD two_sources#{env["PROGSUFFIX"]}",
+    ])
+    expect(File.exists?("two_sources#{env["PROGSUFFIX"]}")).to be_truthy
+    expect(`./two_sources`).to eq "This is a C program with two sources.\n"
+  end
+
+  it "supports dumping an Environment's construction variables" do
+    test_dir("simple")
+    env = Rscons::Environment.new do |env|
+      env["CFLAGS"] += %w[-O2 -fomit-frame-pointer]
+    end
+    env.dump
+    result = lines
+    expect(result.include?(%{CFLAGS => ["-O2", "-fomit-frame-pointer"]})).to be_truthy
+    expect(result.include?(%{CPPPATH => []})).to be_truthy
+  end
+
 end

spec/rscons/builder_spec.rb

@@ -0,0 +1,9 @@
+module Rscons
+  describe Builder do
+    describe "#run" do
+      it "raises an error if called directly and not through a subclass" do
+        expect{subject.run(:target, :sources, :cache, :env, :vars)}.to raise_error /This method must be overridden in a subclass/
+      end
+    end
+  end
+end

spec/rscons/builders/command_spec.rb

@@ -0,0 +1,16 @@
+module Rscons
+  module Builders
+    describe Command do
+      let(:command) { ['pandoc', '-fmarkdown', '-thtml', '-o${_TARGET}', '${_SOURCES}'] }
+      let(:env) {Environment.new}
+      subject {Command.new}
+
+
+      it "invokes the command to build the target" do
+        expected_cmd = ['pandoc', '-fmarkdown', '-thtml', '-ofoo.html', 'foo.md']
+        expect(subject).to receive(:standard_build).with("CMD foo.html", "foo.html", expected_cmd, ["foo.md"], env, :cache)
+        subject.run("foo.html", ["foo.md"], :cache, env, {'CMD' => command})
+      end
+    end
+  end
+end

spec/rscons/builders/object_spec.rb

@@ -2,19 +2,31 @@ module Rscons
   module Builders
     describe Object do
       let(:env) {Environment.new}
+      let(:cache) {double(Cache)}
       subject {Object.new}
 
       it "supports overriding CCCMD construction variable" do
-        cache = "cache"
-        allow(cache).to receive(:up_to_date?) { false }
-        allow(cache).to receive(:mkdir_p) { }
-        allow(cache).to receive(:register_build) { }
-        allow(FileUtils).to receive(:rm_f) { }
-        allow(File).to receive(:exists?) { false }
+        expect(cache).to receive(:up_to_date?).and_return(false)
+        expect(cache).to receive(:mkdir_p)
+        expect(FileUtils).to receive(:rm_f)
         expect(env).to receive(:execute).with("CC mod.o", ["llc", "mod.c"]).and_return(true)
+        expect(File).to receive(:exists?).and_return(false)
+        expect(cache).to receive(:register_build)
+
         subject.run("mod.o", ["mod.c"], cache, env, "CCCMD" => ["llc", "${_SOURCES}"])
       end
 
+      it "supports overriding DEPFILESUFFIX construction variable" do
+        expect(cache).to receive(:up_to_date?).and_return(false)
+        expect(cache).to receive(:mkdir_p)
+        expect(FileUtils).to receive(:rm_f)
+        expect(env).to receive(:execute).with(anything, %w[gcc -c -o f.o -MMD -MF f.d in.c]).and_return(true)
+        expect(File).to receive(:exists?).with("f.d").and_return(false)
+        expect(cache).to receive(:register_build)
+
+        subject.run("f.o", ["in.c"], cache, env, "DEPFILESUFFIX" => ".d")
+      end
+
       it "raises an error when given a source file with an unknown suffix" do
         expect { subject.run("mod.o", ["mod.xyz"], :cache, env, {}) }.to raise_error /unknown input file type: "mod.xyz"/
       end

spec/rscons/builders/simple_builder_spec.rb

@@ -0,0 +1,19 @@
+module Rscons
+  module Builders
+    describe SimpleBuilder do
+      let(:env) {Environment.new}
+
+      it "should create a new builder with the given name (as a symbol) and action" do
+        builder = Rscons::Builders::SimpleBuilder.new(:Foo) { 0x1234 }
+        expect(builder.name).to eq("Foo")
+        expect(builder.run(1,2,3,4,5)).to eq(0x1234)
+      end
+
+      it "should create a new builder with the given name (as a string) and action" do
+        builder = Rscons::Builders::SimpleBuilder.new("Foo") { 0x1234 }
+        expect(builder.name).to eq("Foo")
+        expect(builder.run(1,2,3,4,5)).to eq(0x1234)
+      end
+    end
+  end
+end

spec/rscons/environment_spec.rb

@@ -72,6 +72,13 @@ module Rscons
         env.add_builder(Rscons::Builders::Object.new)
         expect(env.builders.keys).to eq ["Object"]
       end
+
+      it "adds a new simple builder to the list of builders" do
+        env = Environment.new(exclude_builders: true)
+        expect(env.builders.keys).to eq []
+        env.add_builder(:Foo) {}
+        expect(env.builders.keys).to eq ["Foo"]
+      end
     end
 
     describe "#get_build_fname" do
@@ -247,7 +254,7 @@ module Rscons
         env["foo"] = {}
         expect(env.expand_varref(["-p${path}", "${flags}"])).to eq ["-pdir1", "-pdir2", "-x", "-y", "-z"]
         expect(env.expand_varref("foo")).to eq "foo"
-        expect {env.expand_varref("${foo}")}.to raise_error /expand.a.variable.reference/
+        expect {env.expand_varref("${foo}")}.to raise_error /Unknown.varref.type/
         expect(env.expand_varref("${specialflag}")).to eq "-z"
         expect(env.expand_varref("${path}")).to eq ["dir1", "dir2"]
       end
@@ -322,6 +329,13 @@ module Rscons
         env.depends("foo", "bar", "baz")
         expect(env.instance_variable_get(:@user_deps)).to eq({"foo" => ["bar", "baz"]})
       end
+      it "expands arguments for construction variable references" do
+        env = Environment.new
+        env["foo"] = "foo.exe"
+        env["bar"] = "bar.c"
+        env.depends("${foo}", "${bar}", "a.h")
+        expect(env.instance_variable_get(:@user_deps)).to eq({"foo.exe" => ["bar.c", "a.h"]})
+      end
     end
 
     describe "#build_sources" do

spec/rscons/varset_spec.rb

@@ -1,5 +1,6 @@
 module Rscons
   describe VarSet do
+
     describe '#initialize' do
       it "initializes variables from a Hash" do
         v = VarSet.new({"one" => 1, "two" => :two})
@@ -126,26 +127,26 @@ module Rscons
                      "CPPPATH" => ["dir1", "dir2"],
                      "compiler" => "${CC}",
                      "cmd" => ["${CC}", "-c", "${CFLAGS}", "-I${CPPPATH}"],
-                     "hash" => {})
+                     "lambda" => lambda {|args| "#{args[:v]}--12"})
       it "expands to the string itself if the string is not a variable reference" do
-        expect(v.expand_varref("CC")).to eq("CC")
-        expect(v.expand_varref("CPPPATH")).to eq("CPPPATH")
-        expect(v.expand_varref("str")).to eq("str")
+        expect(v.expand_varref("CC", :lambda_args)).to eq("CC")
+        expect(v.expand_varref("CPPPATH", :lambda_args)).to eq("CPPPATH")
+        expect(v.expand_varref("str", :lambda_args)).to eq("str")
       end
       it "expands a single variable reference beginning with a '$'" do
-        expect(v.expand_varref("${CC}")).to eq("gcc")
-        expect(v.expand_varref("${CPPPATH}")).to eq(["dir1", "dir2"])
+        expect(v.expand_varref("${CC}", :lambda_args)).to eq("gcc")
+        expect(v.expand_varref("${CPPPATH}", :lambda_args)).to eq(["dir1", "dir2"])
       end
       it "expands a single variable reference in ${arr} notation" do
-        expect(v.expand_varref("prefix${CFLAGS}suffix")).to eq(["prefix-Wallsuffix", "prefix-O2suffix"])
-        expect(v.expand_varref(v["cmd"])).to eq(["gcc", "-c", "-Wall", "-O2", "-Idir1", "-Idir2"])
+        expect(v.expand_varref("prefix${CFLAGS}suffix", :lambda_args)).to eq(["prefix-Wallsuffix", "prefix-O2suffix"])
+        expect(v.expand_varref(v["cmd"], :lambda_args)).to eq(["gcc", "-c", "-Wall", "-O2", "-Idir1", "-Idir2"])
       end
       it "expands a variable reference recursively" do
-        expect(v.expand_varref("${compiler}")).to eq("gcc")
-        expect(v.expand_varref("${cmd}")).to eq(["gcc", "-c", "-Wall", "-O2", "-Idir1", "-Idir2"])
+        expect(v.expand_varref("${compiler}", :lambda_args)).to eq("gcc")
+        expect(v.expand_varref("${cmd}", :lambda_args)).to eq(["gcc", "-c", "-Wall", "-O2", "-Idir1", "-Idir2"])
       end
       it "resolves multiple variable references in one element by enumerating all combinations" do
-        expect(v.expand_varref("cflag: ${CFLAGS}, cpppath: ${CPPPATH}, compiler: ${compiler}")).to eq([
+        expect(v.expand_varref("cflag: ${CFLAGS}, cpppath: ${CPPPATH}, compiler: ${compiler}", :lambda_args)).to eq([
           "cflag: -Wall, cpppath: dir1, compiler: gcc",
           "cflag: -O2, cpppath: dir1, compiler: gcc",
           "cflag: -Wall, cpppath: dir2, compiler: gcc",
@@ -153,11 +154,50 @@ module Rscons
         ])
       end
       it "returns an empty string when a variable reference refers to a non-existent variable" do
-        expect(v.expand_varref("${not_here}")).to eq("")
+        expect(v.expand_varref("${not_here}", :lambda_args)).to eq("")
       end
-      it "raises an error when a variable reference refers to an unhandled type" do
-        expect { v.expand_varref("${hash}") }.to raise_error /I do not know how to expand a variable reference to a Hash/
+      it "calls a lambda with the given lambda arguments" do
+        expect(v.expand_varref("${lambda}", [v: "fez"])).to eq("fez--12")
+      end
+      it "raises an error when given an invalid argument" do
+        expect { v.expand_varref({a: :b}, :lambda_args) }.to raise_error /Unknown varref type: Hash/
+      end
+      it "raises an error when an expanded variable is an unexpected type" do
+        expect(v).to receive(:[]).at_least(1).times.with("bad").and_return("bad_val")
+        expect(v).to receive(:expand_varref).with("bad_val", :lambda_args).and_return({a: :b})
+        expect(v).to receive(:expand_varref).and_call_original
+        expect { v.expand_varref("${bad}", :lambda_args) }.to raise_error /I do not know how to expand a variable reference to a Hash/
       end
     end
+
+    describe "#to_h" do
+      it "returns a Hash of all variables in the VarSet" do
+        v = VarSet.new({"fuz" => "a string", "foo" => 42, "bar" => :baz,
+                        "qax" => [3, 6], "qux" => {a: :b}})
+        v2 = v.merge("baz" => "qux", "qax" => [4, 7])
+        v3 = v2.merge("fuz" => nil)
+        v4 = v3.clone
+        v4["fuz"] = :fuzzy
+        v4["foo"] = 43
+        expect(v.to_h).to eq({
+          "fuz" => "a string", "foo" => 42, "bar" => :baz,
+          "qax" => [3, 6], "qux" => {a: :b},
+        })
+        expect(v2.to_h).to eq({
+          "fuz" => "a string", "foo" => 42, "bar" => :baz,
+          "qax" => [4, 7], "qux" => {a: :b}, "baz" => "qux",
+        })
+        expect(v3.to_h).to eq({
+          "fuz" => nil, "foo" => 42, "bar" => :baz,
+          "qax" => [4, 7], "qux" => {a: :b}, "baz" => "qux",
+        })
+        expect(v4.to_h).to eq({
+          "fuz" => :fuzzy, "foo" => 43, "bar" => :baz,
+          "qax" => [4, 7], "qux" => {a: :b}, "baz" => "qux",
+        })
+        expect(VarSet.new.to_h).to eq({})
+      end
+    end
+
   end
 end