A mojom .d generator.

mojom/mojom_parser/generators/common/common.go

Index: mojom/mojom_parser/generators/common/common.go
diff --git a/mojom/mojom_parser/generators/common/common.go b/mojom/mojom_parser/generators/common/common.go
new file mode 100644
index 0000000000000000000000000000000000000000..829442b192ff1975126abbb178ec7ef264214080
--- /dev/null
+++ b/mojom/mojom_parser/generators/common/common.go
@@ -0,0 +1,60 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package common
+
+import (
+	"mojom/mojom_parser/generated/mojom_files"
+)
+
+// common groups together functions which make it easier for generators
+// implemented in go to implement the same interface.
+
+// GeneratorConfig is used to specify configuration for a generator.
+type GeneratorConfig interface {
+	// FileGraph returns a parsed MojomFileGraph.
+	FileGraph() *mojom_files.MojomFileGraph
+
+	// OutputDir returns an absolute path in which generator output must be
+	// written.
+	OutputDir() string
+
+	// SrcRootPath returns an absolute path to the root of the source tree. This
+	// is used to compute the relative path from the root of the source tree to
+	// mojom files for which output is to be generated.
+	SrcRootPath() string
+
+	// GenImports returns true if all files in the provided file graph should
+	// be generated and and false if only the files for which a SpecifiedFileName
+	// is specified should be generated.
+	GenImports() bool

[rudominer, 2016/02/27 01:28:10]

My suggestion for a more complete description. Do with it as you will:

GenImports returns true if the generator should generate output files for all of
the files in the provided file graph, including those that were not specified on
the command line but are only present because they were referenced in an import
statement. It returns false if the generator should generate output files only
for the files which were explicitly specified (as indicated by the fact that
they have a non-empty |SpecifiedFileName|).

[azani, 2016/02/29 21:28:32]

Done.

+}
+
+// Writer is the interface used by the generators to write their output.
+// It is also made to faciliate testing by allowing generator code to write
+// to a provided buffer such as a bytes.Buffer.
+type Writer interface {
+	WriteString(s string) (n int, err error)
+}
+
+// writeOutput is the type of the generator function which writes the specified
+// file's generated code to the writer.
+type writeOutput func(fileName string, config GeneratorConfig, writer Writer)
+
+// getOutputWriter is the type of the generator function which decides where
+// the generated code for a particular file is to be written.
+// This allows generators to decide where they should write their output to.
+type getOutputWriter func(fileName string, config GeneratorConfig) Writer
+
+// GenerateOutput iterates through the files in the file graph in config and

[rudominer, 2016/02/27 01:28:10]

config -> |config|

[azani, 2016/02/29 21:28:32]

Done.

+// for all the files for which an output should be generated, it uses
+// writeOutput to write the output to the location specified by getOutputWriter.
+func GenerateOutput(writeOutput writeOutput, getOutputWriter getOutputWriter, config GeneratorConfig) {
+	for fileName, file := range config.FileGraph().Files {
+		if config.GenImports() || *file.SpecifiedFileName != "" {
+			writer := getOutputWriter(fileName, config)
+			writeOutput(fileName, config, writer)

[rudominer, 2016/02/27 01:28:10]

getOutputWriter isn't really helping here and instead is mandating a separation
that not all implementers might want. How about:

func GenerateOutput(generateFile generateFile, config GeneratorConfig) {
     for fileName, file := range config.FileGraph().Files {
         if config.GenImports() || *file.SpecifiedFileName != "" {
             generateFile(fileName, config)
}

[azani, 2016/02/29 21:28:32]

I prefer this decoupling because it means that it's always possible to pass in a
different writer to writeOutput for testing purposes.

+		}
+	}
+}