Use protobuf instead of dot to communicate between parsers and core

that is, between the language-specific parsers and the language-agnostic core.

.bazelrc

@@ -0,0 +1,2 @@
+# Avoid downloading protobuf twice:
+build --proto_toolchain_for_java="@com_google_protobuf//:java_toolchain"

WORKSPACE

@@ -2,3 +2,11 @@ load("//thirdparty:workspace.bzl", "maven_dependencies")
 load("//thirdparty:load.bzl", "declare_maven")
 
 maven_dependencies(declare_maven)
+
+# Provide dependencies for proto_library and java_proto_library rules.
+http_archive(
+    name = "com_google_protobuf",
+    urls = ["https://github.com/google/protobuf/releases/download/v3.4.1/protobuf-java-3.4.1.zip"],
+    strip_prefix = "protobuf-3.4.1",
+    sha256 = "091e1aa2b64ea6d512ff9294ecc9da95132c3b961a8fb39a3bab3929e5122f50",
+)

src/main/java/com/google/devtools/build/bfg/BUILD

@@ -20,15 +20,6 @@ java_library(
     ],
 )
 
-java_library(
-    name = "DotFileParser",
-    srcs = ["DotFileParser.java"],
-    deps = [
-        "//thirdparty/jvm/com/google/guava",
-        "//thirdparty/jvm/com/google/re2j",
-    ],
-)
-
 java_library(
     name = "GraphProcessor",
     srcs = [
@@ -91,10 +82,10 @@ java_library(
         "Bfg.java",
     ],
     deps = [
+        ":bfg_java_proto",
         ":BuildRule",
         ":BuildozerCommandCreator",
         ":ClassToRuleResolver",
-        ":DotFileParser",
         ":ExternalResolver",
         ":GraphProcessor",
         "//thirdparty/jvm/args4j",
@@ -117,6 +108,7 @@ java_library(
         "JavaSourceFileParserCli.java",
     ],
     deps = [
+        ":bfg_java_proto",
         ":ReferencedClassesParser",
         "//thirdparty/jvm/args4j",
         "//thirdparty/jvm/com/google/guava",
@@ -163,3 +155,13 @@ java_library(
         "//thirdparty/jvm/com/google/guava",
     ],
 )
+
+proto_library(
+    name = "bfg_proto",
+    srcs = ["bfg.proto"],
+)
+
+java_proto_library( 
+    name = "bfg_java_proto"
+, deps = [":bfg_proto" ], 
+)

src/main/java/com/google/devtools/build/bfg/Bfg.java

@@ -21,13 +21,14 @@
 import static com.google.devtools.build.bfg.BuildozerCommandCreator.computeBuildozerCommands;
 import static com.google.devtools.build.bfg.BuildozerCommandCreator.getBuildFilesForBuildozer;
 import static com.google.devtools.build.bfg.ClassGraphPreprocessor.preProcessClassGraph;
-import static com.google.devtools.build.bfg.DotFileParser.getDirectedGraphFromDotFile;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Splitter;
 import com.google.common.collect.ImmutableList;
+import com.google.common.graph.GraphBuilder;
 import com.google.common.graph.ImmutableGraph;
+import com.google.common.graph.MutableGraph;
 import com.google.re2j.Pattern;
 import java.io.BufferedInputStream;
 import java.io.BufferedReader;
@@ -39,9 +40,11 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.List;
+import java.util.Map;
 import java.util.Scanner;
 import org.kohsuke.args4j.CmdLineParser;
 import org.kohsuke.args4j.Option;
+import protos.com.google.devtools.build.bfg.Bfg.ParserOutput;
 
 /** Entry point to the BUILD file generator. */
 public class Bfg {
@@ -108,6 +111,7 @@ private void run(String[] args) throws Exception {
     cmdLineParser.parseArgument(args);
 
     List<String> dotFile = readDotFileFromStdIn();
+    ParserOutput parserOutput = ParserOutput.parseFrom(System.in);
     if (dotFile.isEmpty()) {
       explainUsageErrorAndExit(cmdLineParser, "Expected nonempty class graph as input");
     }
@@ -118,7 +122,8 @@ private void run(String[] args) throws Exception {
     Pattern blackList = compilePattern(cmdLineParser, blackListRegex);
 
     ImmutableGraph<String> classGraph =
-        preProcessClassGraph(getDirectedGraphFromDotFile(dotFile), whiteList, blackList);
+        preProcessClassGraph(
+            protoMultimapToGraph(parserOutput.getClassToClassMap()), whiteList, blackList);
 
     ImmutableList<Path> contentRoots =
         stream(Splitter.on(',').split(contentRootPaths))
@@ -148,6 +153,18 @@ private void run(String[] args) throws Exception {
     executeBuildozerCommands(buildRuleGraph, workspace, isDryRun, buildozerPath);
   }
 
+  private ImmutableGraph<String> protoMultimapToGraph(
+      Map<String, protos.com.google.devtools.build.bfg.Bfg.Strings> m) {
+    MutableGraph<String> result = GraphBuilder.directed().build();
+    m.forEach(
+        (u, deps) -> {
+          for (String s : deps.getSList()) {
+            result.putEdge(u, s);
+          }
+        });
+    return ImmutableGraph.copyOf(result);
+  }
+
   private static Pattern compilePattern(CmdLineParser cmdLineParser, String patternString) {
     try {
       return Pattern.compile(patternString);

src/main/java/com/google/devtools/build/bfg/JavaSourceFileParserCli.java

@@ -27,13 +27,16 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.logging.Logger;
 import org.kohsuke.args4j.Argument;
 import org.kohsuke.args4j.CmdLineException;
 import org.kohsuke.args4j.CmdLineParser;
 import org.kohsuke.args4j.Option;
+import protos.com.google.devtools.build.bfg.Bfg;
 
 /**
  * Entry point to BFG java source file parser. Given a list of source files, it prints a graph viz
@@ -104,15 +107,19 @@ private void run(String[] args) throws Exception {
       logger.warning(
           String.format("Class Names not found %s", Joiner.on("\n\t").join(unresolvedClassNames)));
     }
-    printDotFileContent(classDepsGraph);
+    Bfg.ParserOutput.Builder result = Bfg.ParserOutput.newBuilder();
+    result.putAllClassToClass(writeGraphToProtoMap(classDepsGraph));
+    result.build().writeTo(System.out);
   }
 
-  /** Given a directed graph, generates the content of desired dot file */
-  private static void printDotFileContent(ImmutableGraph<String> depsGraph) {
-    System.out.println("digraph \"depsgraph\" {");
-    for (EndpointPair<String> edge : depsGraph.edges()) {
-      System.out.printf("\t\"%s\" -> \"%s\";%n", edge.nodeU(), edge.nodeV());
+  private static HashMap<String, Bfg.Strings> writeGraphToProtoMap(
+      ImmutableGraph<String> graph) {
+    HashMap<String, Bfg.Strings> result = new HashMap<>();
+    for (String u : graph.nodes()) {
+      Bfg.Strings.Builder adj = Bfg.Strings.newBuilder();
+      adj.addAllS(graph.adjacentNodes(u));
+      result.put(u, adj.build());
     }
-    System.out.println("}");
+    return result;
   }
 }

src/main/java/com/google/devtools/build/bfg/bfg.proto

@@ -0,0 +1,19 @@
+syntax = "proto2";
+
+package com.google.devtools.build.bfg;
+
+option java_package = "protos.com.google.devtools.build.bfg";
+
+// ParserOutput is used to communicate between language-specific parsers and the language-agnostic
+// BFG core.
+message ParserOutput {
+    // The class dependency graph.
+    // In the Java case, we have (u, v) if 'u' mentions [1] 'v'.
+    // [1] - By mention, we mean either imports or references in code, either as a fully qualified
+    //       name, or an implied same-package name.
+    map<string, Strings> class_to_class = 1;
+}
+
+message Strings {
+    repeated string s = 1;
+}

src/test/java/com/google/devtools/build/bfg/BUILD

@@ -1,17 +1,5 @@
 licenses(["notice"])  # Apache 2.0
 
-java_test(
-    name = "DotFileParserTest",
-    srcs = ["DotFileParserTest.java"],
-    deps = [
-        "//src/main/java/com/google/devtools/build/bfg:DotFileParser",
-        "//thirdparty/jvm/com/google/guava",
-        "//thirdparty/jvm/com/google/re2j",
-        "//thirdparty/jvm/com/google/truth",
-        "//thirdparty/jvm/junit",
-    ],
-)
-
 java_test(
     name = "GraphProcessorTest",
     srcs = ["GraphProcessorTest.java"],