raise error when circular dependencies are found - close #38

build_tests/simple/error_circular_dependency.rb

@@ -0,0 +1,5 @@
+Rscons::Environment.new do |env|
+  env.Command("foo", "bar")
+  env.Command("bar", "baz")
+  env.Command("baz", "foo")
+end

build_tests/simple/error_circular_dependency2.rb

@@ -0,0 +1,3 @@
+Rscons::Environment.new do |env|
+  env.Command("foo", "foo")
+end

lib/rscons/job_set.rb

@@ -47,12 +47,18 @@ module Rscons
     # @return [nil, Hash]
     #   The next job to run.
     def get_next_job_to_run(targets_still_building)
+      targets_skipped = Set.new
       @jobs.keys.each do |target|
         skip = false
         (@jobs[target][0][:sources] + (@build_dependencies[target] || []).to_a).each do |src|
           if @jobs.include?(src)
+            if targets_skipped.include?(src) or (src == target)
+              # We have encountered a circular dependency.
+              raise "Circular build dependency for #{src}"
+            end
             # Skip this target because it depends on another target later in
             # the job set.
+            targets_skipped << target
             skip = true
             break
           end

spec/build_tests_spec.rb

@@ -732,6 +732,20 @@ EOF
     expect(`./test-static.exe`).to match /Hi from one/
   end
 
+  it "raises an error for a circular dependency" do
+    test_dir("simple")
+    result = run_test(rsconsfile: "error_circular_dependency.rb")
+    expect(result.stderr).to match /Circular build dependency for (foo|bar|baz)/
+    expect(result.status).to_not eq 0
+  end
+
+  it "raises an error for a circular dependency where a build target contains itself in its source list" do
+    test_dir("simple")
+    result = run_test(rsconsfile: "error_circular_dependency2.rb")
+    expect(result.stderr).to match /Circular build dependency for foo/
+    expect(result.status).to_not eq 0
+  end
+
   context "backward compatibility" do
     it "allows a builder to call Environment#run_builder in a non-threaded manner" do
       test_dir("simple")