v5.3.0

CHANGELOG.md

@@ -1,3 +1,11 @@
+## v5.3.0
+
+### New Features
+
+- Warn about unused rules (rules not reachable from any start rule). The
+  warnings are written to the log file and, with `-w`, are printed to stderr
+  and treated as fatal errors.
+
 ## v5.2.0
 
 ### New Features

Gemfile.lock

@@ -2,17 +2,27 @@ GEM
   remote: https://rubygems.org/
   specs:
     base64 (0.3.0)
-    date (3.5.1)
     diff-lcs (1.6.2)
-    docile (1.4.1)
-    erb (6.0.4)
-    psych (5.4.0)
-      date
-      stringio
+    erb (6.0.7)
+    logger (1.7.0)
+    prism (2.1.0)
+    prism (2.1.0-aarch64-linux-gnu)
+    prism (2.1.0-aarch64-linux-musl)
+    prism (2.1.0-arm-linux-gnu)
+    prism (2.1.0-arm-linux-musl)
+    prism (2.1.0-arm64-darwin)
+    prism (2.1.0-x86_64-darwin)
+    prism (2.1.0-x86_64-linux-gnu)
+    prism (2.1.0-x86_64-linux-musl)
     rake (13.4.2)
-    rdoc (7.2.0)
+    rbs (4.2.0)
+      logger
+      prism (>= 1.6.0)
+      tsort
+    rdoc (8.1.0)
       erb
-      psych (>= 4.0.0)
+      prism (>= 1.6.0)
+      rbs (>= 4.0.0)
       tsort
     redcarpet (3.6.1)
     rspec (3.13.2)
@@ -28,18 +38,20 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
     rspec-support (3.13.7)
-    simplecov (0.22.0)
-      docile (~> 1.1)
-      simplecov-html (~> 0.11)
-      simplecov_json_formatter (~> 0.1)
-    simplecov-html (0.13.2)
-    simplecov_json_formatter (0.1.4)
-    stringio (3.2.0)
+    simplecov (1.3.2)
     syntax (1.2.2)
     tsort (0.2.0)
 
 PLATFORMS
+  aarch64-linux-gnu
+  aarch64-linux-musl
+  arm-linux-gnu
+  arm-linux-musl
+  arm64-darwin
   ruby
+  x86_64-darwin
+  x86_64-linux-gnu
+  x86_64-linux-musl
 
 DEPENDENCIES
   base64

README.md

@@ -39,8 +39,8 @@ Propane is typically invoked from the command-line as `./propane`.
                   debugging a grammar.
       --version   Show program version and exit.
       -w          Treat warnings as errors. This option will treat shift/reduce
-                  conflicts as fatal errors and will print them to stderr in
-                  addition to the log file.
+                  conflicts and unused rules as fatal errors and will print
+                  them to stderr in addition to the log file.
 
 The user must specify the path to a Propane input grammar file and a path to an
 output file.

doc/user_guide.md

@@ -43,8 +43,8 @@ Propane is typically invoked from the command-line as `./propane`.
                   debugging a grammar.
       --version   Show program version and exit.
       -w          Treat warnings as errors. This option will treat shift/reduce
-                  conflicts as fatal errors and will print them to stderr in
-                  addition to the log file.
+                  conflicts and unused rules as fatal errors and will print
+                  them to stderr in addition to the log file.
 
 The user must specify the path to a Propane input grammar file and a path to an
 output file.

lib/propane/cli.rb

@@ -10,8 +10,8 @@ Options:
               debugging a grammar.
   --version   Show program version and exit.
   -w          Treat warnings as errors. This option will treat shift/reduce
-              conflicts as fatal errors and will print them to stderr in
-              addition to the log file.
+              conflicts and unused rules as fatal errors and will print
+              them to stderr in addition to the log file.
 EOF
 
     class << self

lib/propane/parser.rb

@@ -50,6 +50,7 @@ class Propane
 
       build_reduce_actions!
       build_tables!
+      check_unused_rules!
       write_log!
       errormessage = ""
       if @errors.size > 0
@@ -68,6 +69,34 @@ class Propane
 
     private
 
+    # Record a warning for each user-defined rule that cannot be reached from
+    # any start rule.
+    #
+    # @return [void]
+    def check_unused_rules!
+      reachable = Set.new
+      pending = @grammar.rules[0...@grammar.start_rules.length].map(&:rule_set)
+      while rule_set = pending.pop
+        next if reachable.include?(rule_set)
+        reachable << rule_set
+        rule_set.rules.each do |rule|
+          rule.components.each do |component|
+            if component.is_a?(RuleSet) && !reachable.include?(component)
+              pending << component
+            end
+          end
+        end
+      end
+      @rule_sets.each do |name, rule_set|
+        # Skip rule sets generated internally (real start rules and optional
+        # component rules).
+        next if name.start_with?("$") || rule_set.optional?
+        unless reachable.include?(rule_set)
+          @warnings << "Unused rule #{name} (defined on line #{rule_set.rules.first.line_number})"
+        end
+      end
+    end
+
     def build_tables!
       @state_table = []
       @shift_table = []

lib/propane/version.rb

@@ -1,3 +1,3 @@
 class Propane
-  VERSION = "5.2.0"
+  VERSION = "5.3.0"
 end

spec/propane_spec.rb

@@ -45,7 +45,7 @@ SimpleCov.start do
   # suite. The parts are merged once at the end by the spec Rake task.
   coverage_dir(#{"coverage/parts/#{command_name}".inspect})
   filters.clear
-  add_filter do |src|
+  skip do |src|
     !(src.filename[SimpleCov.root])
   end
   formatter(MyFormatter)
@@ -267,6 +267,50 @@ EOF
     expect(File.binread("spec/run/testparser.log")).to match %r{Shift/Reduce conflict \(state \d+\) between token b and rule As2\? \(defined on line 4\)}
   end
 
+  it "warns on unused rules" do
+    write_grammar <<EOF
+token a;
+token b;
+Start -> a;
+Unused -> b Other?;
+Other -> a;
+EOF
+    results = run_propane(capture: true)
+    expect(results.stderr).to eq ""
+    expect(results.status).to eq 0
+    log = File.binread("spec/run/testparser.log")
+    expect(log).to match %r{Unused rule Unused \(defined on line 4\)}
+    expect(log).to match %r{Unused rule Other \(defined on line 5\)}
+    expect(log).to_not match %r{Unused rule (Start|Other\?)}
+  end
+
+  it "errors on unused rules with -w" do
+    write_grammar <<EOF
+token a;
+token b;
+Start -> a Used;
+Used -> b;
+Unused -> b;
+EOF
+    results = run_propane(extra_args: %w[-w], capture: true)
+    expect(results.stderr).to match %r{Unused rule Unused \(defined on line 5\)}
+    expect(results.stderr).to_not match %r{Unused rule (Start|Used)\b}
+    expect(results.status).to_not eq 0
+  end
+
+  it "does not warn about rules reachable from any of multiple start rules" do
+    write_grammar <<EOF
+token a;
+token b;
+start Start Other;
+Start -> a;
+Other -> b;
+EOF
+    results = run_propane(extra_args: %w[-w], capture: true)
+    expect(results.stderr).to eq ""
+    expect(results.status).to eq 0
+  end
+
   it "errors on duplicate field aliases in a rule" do
     write_grammar <<EOF
 token a;

spec/spec_helper.rb

@@ -7,8 +7,8 @@ unless ENV["dist_specs"]
     end
   end
   SimpleCov.start do
-    add_filter "/spec/"
-    add_filter "/.bundle/"
+    skip "/spec/"
+    skip "/.bundle/"
     if ENV["partial_specs"]
       command_name "RSpec-partial"
     else