Add a dependency fixer for proto deps

protoc dependency files, at least for C++ outputs, uses the form of:

  a/b.c \
  a/b.h: <dep1> <dep2>...

Ninja will fail the command when it parses a dep file and there's more
than one output file (even though it doesn't care what the output file
name is). So this tool will parse the original file, and output a
version with only a single output file.

Bug: 67329638
Test: NINJA_ARGS="-t deps ...pb.c" m
Test: NINJA_ARGS="-t deps ...srcjar" m
Test: NINJA_ARGS="-t deps ...srcszip" m
Test: Run dep_fixer across all of taimen's dep files, no failures.
Test: Run dep_fixer against the processed files, no changes.
Test: Run androidmk across all of our Android.mk files, inspect the diffs
Change-Id: I4263b7d5faea37285afa6b24dedf5964aa7d19dc

1 files changed, 67 insertions, 0 deletions

diff --git a/cmd/dep_fixer/main.go b/cmd/dep_fixer/main.go
new file mode 100644
index 00000000..bac3772b
--- /dev/null
+++ b/cmd/dep_fixer/main.go
@@ -0,0 +1,67 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This tool reads "make"-like dependency files, and outputs a canonical version
+// that can be used by ninja. Ninja doesn't support multiple output files (even
+// though it doesn't care what the output file is, or whether it matches what is
+// expected).
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+)
+
+func main() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s <depfile.d>")
+		flag.PrintDefaults()
+	}
+	output := flag.String("o", "", "Optional output file (defaults to rewriting source if necessary)")
+	flag.Parse()
+
+	if flag.NArg() != 1 {
+		log.Fatal("Expected a single file as an argument")
+	}
+
+	old, err := ioutil.ReadFile(flag.Arg(0))
+	if err != nil {
+		log.Fatalf("Error opening %q: %v", flag.Arg(0), err)
+	}
+
+	deps, err := Parse(flag.Arg(0), bytes.NewBuffer(append([]byte(nil), old...)))
+	if err != nil {
+		log.Fatalf("Failed to parse: %v", err)
+	}
+
+	new := deps.Print()
+
+	if *output == "" || *output == flag.Arg(0) {
+		if !bytes.Equal(old, new) {
+			err := ioutil.WriteFile(flag.Arg(0), new, 0666)
+			if err != nil {
+				log.Fatalf("Failed to write: %v", err)
+			}
+		}
+	} else {
+		err := ioutil.WriteFile(*output, new, 0666)
+		if err != nil {
+			log.Fatalf("Failed to write to %q: %v", *output, err)
+		}
+	}
+}