support phony targets - close #25

lib/rscons.rb

@@ -65,6 +65,15 @@ module Rscons
     path =~ %r{^(/|\w:[\\/])}
   end
 
+  # Return whether the given target is a phony target.
+  #
+  # @param target [Symbol, String] Target name.
+  #
+  # @return [Boolean] Whether the given target is a phony target.
+  def self.phony_target?(target)
+    target.is_a?(Symbol)
+  end
+
   # Return a new path by changing the suffix in path to suffix.
   #
   # @param path [String] The path to alter.

lib/rscons/builder.rb

@@ -87,8 +87,10 @@ module Rscons
     #   The name of the target on success or false on failure.
     def standard_build(short_cmd_string, target, command, sources, env, cache)
       unless cache.up_to_date?(target, command, sources, env)
-        cache.mkdir_p(File.dirname(target))
-        FileUtils.rm_f(target)
+        unless Rscons.phony_target?(target)
+          cache.mkdir_p(File.dirname(target))
+          FileUtils.rm_f(target)
+        end
         return false unless env.execute(short_cmd_string, command)
         cache.register_build(target, command, sources, env)
       end

lib/rscons/cache.rb

@@ -56,6 +56,9 @@ module Rscons
     # Name of the file to store cache information in
     CACHE_FILE = ".rsconscache"
 
+    # Prefix for phony cache entries.
+    PHONY_PREFIX = ":PHONY:"
+
     # Create a Cache object and load in the previous contents from the cache
     # file.
     def initialize
@@ -92,7 +95,8 @@ module Rscons
 
     # Check if target(s) are up to date.
     #
-    # @param targets [String, Array<String>] The name(s) of the target file(s).
+    # @param targets [Symbol, 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
@@ -120,19 +124,25 @@ module Rscons
     #     stored in the cache file
     def up_to_date?(targets, command, deps, env, options = {})
       Array(targets).each do |target|
-        # target file must exist on disk
-        return false unless File.exists?(target)
+        cache_key = get_cache_key(target)
+
+        unless Rscons.phony_target?(target)
+          # target file must exist on disk
+          return false unless File.exists?(target)
+        end
 
         # target must be registered in the cache
-        return false unless @cache["targets"].has_key?(target)
+        return false unless @cache["targets"].has_key?(cache_key)
 
-        # target must have the same checksum as when it was built last
-        return false unless @cache["targets"][target]["checksum"] == lookup_checksum(target)
+        unless Rscons.phony_target?(target)
+          # target must have the same checksum as when it was built last
+          return false unless @cache["targets"][cache_key]["checksum"] == lookup_checksum(target)
+        end
 
         # command used to build target must be identical
-        return false unless @cache["targets"][target]["command"] == Digest::MD5.hexdigest(command.inspect)
+        return false unless @cache["targets"][cache_key]["command"] == Digest::MD5.hexdigest(command.inspect)
 
-        cached_deps = @cache["targets"][target]["deps"] || []
+        cached_deps = @cache["targets"][cache_key]["deps"] || []
         cached_deps_fnames = cached_deps.map { |dc| dc["fname"] }
         if options[:strict_deps]
           # depedencies passed in must exactly equal those in the cache
@@ -144,7 +154,7 @@ module Rscons
 
         # set of user dependencies must match
         user_deps = env.get_user_deps(target) || []
-        cached_user_deps = @cache["targets"][target]["user_deps"] || []
+        cached_user_deps = @cache["targets"][cache_key]["user_deps"] || []
         cached_user_deps_fnames = cached_user_deps.map { |dc| dc["fname"] }
         return false unless user_deps == cached_user_deps_fnames
 
@@ -159,7 +169,8 @@ module Rscons
 
     # Store cache information about target(s) built by a builder.
     #
-    # @param targets [String, Array<String>] The name of the target(s) built.
+    # @param targets [Symbol, 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
@@ -172,9 +183,10 @@ module Rscons
     # @return [void]
     def register_build(targets, command, deps, env)
       Array(targets).each do |target|
-        @cache["targets"][target] = {
+        target_checksum = Rscons.phony_target?(target) ? "" : calculate_checksum(target)
+        @cache["targets"][get_cache_key(target)] = {
           "command" => Digest::MD5.hexdigest(command.inspect),
-          "checksum" => calculate_checksum(target),
+          "checksum" => target_checksum,
           "deps" => deps.map do |dep|
             {
               "fname" => dep,
@@ -228,6 +240,21 @@ module Rscons
 
     private
 
+    # Return a String key based on the target name to use in the on-disk cache.
+    #
+    # @param target_name [Symbol, String]
+    #   Target name.
+    #
+    # @return [String]
+    #   Key name.
+    def get_cache_key(target_name)
+      if Rscons.phony_target?(target_name)
+        PHONY_PREFIX + target_name.to_s
+      else
+        target_name
+      end
+    end
+
     # Create a Cache object and load in the previous contents from the cache
     # file.
     def initialize!

lib/rscons/varset.rb

@@ -116,6 +116,8 @@ module Rscons
         expand_varref(varref[*lambda_args], lambda_args)
       elsif varref.nil?
         nil
+      elsif varref.is_a?(Symbol)
+        varref
       else
         raise "Unknown varref type: #{varref.class} (#{varref.inspect})"
       end

spec/build_tests_spec.rb

@@ -932,4 +932,35 @@ EOF
     end
   end
 
+  context "phony targets" do
+    it "allows specifying a Symbol as a target name and reruns the builder if the sources or command have changed" do
+      test_dir("simple")
+      env = Rscons::Environment.new do |env|
+        env.add_builder(:Checker) do |target, sources, cache, env, vars|
+          unless cache.up_to_date?(target, :Checker, sources, env)
+            puts "Checker #{sources.first}" if env.echo != :off
+            cache.register_build(target, :Checker, sources, env)
+          end
+          target
+        end
+        env.Program("simple.exe", "simple.c")
+        env.Checker(:checker, "simple.exe")
+      end
+      expect(lines).to eq(["CC simple.o", "LD simple.exe", "Checker simple.exe"])
+
+      env.clone do |env|
+        env.Checker(:checker, "simple.exe")
+      end
+      expect(lines).to eq([])
+
+      File.open("simple.exe", "w") do |fh|
+        fh.puts "Changed simple.exe"
+      end
+      env.clone do |env|
+        env.Checker(:checker, "simple.exe")
+      end
+      expect(lines).to eq(["Checker simple.exe"])
+    end
+  end
+
 end