Add browser and module field support to package.json processing

Closes #2598

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=164176438

src/com/google/javascript/jscomp/CompilerOptions.java

@@ -1169,6 +1169,15 @@ public void setWrapGoogModulesForWhitespaceOnly(boolean enable) {
   /** Which algorithm to use for locating ES6 and CommonJS modules */
   ModuleLoader.ResolutionMode moduleResolutionMode;
 
+  /** Which entries to look for in package.json files when processing modules */
+  List<String> packageJsonEntryNames;
+
+  /**
+   * Needed by {@link RewriteJsonToModule}, but defined here because RewriteJsonToModule is not
+   * part of the core build.
+   */
+  public static final String PACKAGE_JSON_MAIN = "main";
+
   /**
    * Should the compiler print its configuration options to stderr when they are initialized?
    *
@@ -1194,6 +1203,7 @@ public CompilerOptions() {
 
     // Modules
     moduleResolutionMode = ModuleLoader.ResolutionMode.BROWSER;
+    packageJsonEntryNames = ImmutableList.of(CompilerOptions.PACKAGE_JSON_MAIN);
 
     // Checks
     skipNonTranspilationPasses = false;
@@ -2781,6 +2791,14 @@ public void setModuleResolutionMode(ModuleLoader.ResolutionMode mode) {
     this.moduleResolutionMode = mode;
   }
 
+  public List<String> getPackageJsonEntryNames() {
+    return this.packageJsonEntryNames;
+  }
+
+  public void setPackageJsonEntryNames(List<String> names) {
+    this.packageJsonEntryNames = names;
+  }
+
   /** Serializes compiler options to a stream. */
   @GwtIncompatible("ObjectOutputStream")
   public void serialize(OutputStream objectOutputStream) throws IOException {

src/com/google/javascript/jscomp/RewriteJsonToModule.java

@@ -21,6 +21,7 @@
 import com.google.javascript.rhino.IR;
 import com.google.javascript.rhino.Node;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -35,7 +36,6 @@ public class RewriteJsonToModule extends NodeTraversal.AbstractPostOrderCallback
     implements CompilerPass {
   public static final DiagnosticType JSON_UNEXPECTED_TOKEN =
       DiagnosticType.error("JSC_JSON_UNEXPECTED_TOKEN", "Unexpected JSON token");
-
   private final Map<String, String> packageJsonMainEntries;
   private final AbstractCompiler compiler;
 
@@ -136,10 +136,16 @@ private void visitScript(NodeTraversal t, Node n, Node parent) {
 
     String inputPath = t.getInput().getSourceFile().getOriginalPath();
     if (inputPath.endsWith("/package.json") && jsonObject.isObjectLit()) {
-      Node main = NodeUtil.getFirstPropMatchingKey(jsonObject, "main");
-      if (main != null && main.isString()) {
-        String dirName = inputPath.substring(0, inputPath.length() - "package.json".length());
-        packageJsonMainEntries.put(inputPath, dirName + main.getString());
+      List<String> possibleMainEntries = compiler.getOptions().getPackageJsonEntryNames();
+
+      for (String entryName : possibleMainEntries) {
+        Node entry = NodeUtil.getFirstPropMatchingKey(jsonObject, entryName);
+
+        if (entry != null && entry.isString()) {
+          String dirName = inputPath.substring(0, inputPath.length() - "package.json".length());
+          packageJsonMainEntries.put(inputPath, dirName + entry.getString());
+          break;
+        }
       }
     }
 

test/com/google/javascript/jscomp/RewriteJsonToModuleTest.java

@@ -18,6 +18,7 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
+import com.google.common.collect.ImmutableList;
 import com.google.javascript.jscomp.deps.ModuleLoader;
 import com.google.javascript.rhino.Node;
 
@@ -40,6 +41,8 @@ protected CompilerOptions getOptions() {
     // Trigger module processing after parsing.
     options.setProcessCommonJSModules(true);
     options.setModuleResolutionMode(ModuleLoader.ResolutionMode.NODE);
+    options.setPackageJsonEntryNames(
+        ImmutableList.of("browser", CompilerOptions.PACKAGE_JSON_MAIN));
     return options;
   }
 
@@ -50,18 +53,18 @@ protected int getNumRepetitions() {
 
   public void testJsonFile() {
     test(
-        srcs(SourceFile.fromCode("/test.json", "{ \"foo\": \"bar\"}")),
-        expected("goog.provide('module$test_json'); var module$test_json = { \"foo\": \"bar\"};"));
+        srcs(SourceFile.fromCode("/test.json", "{ 'foo': 'bar'}")),
+        expected("goog.provide('module$test_json'); var module$test_json = { 'foo': 'bar'};"));
 
     assertEquals(0, getLastCompiler().getModuleLoader().getPackageJsonMainEntries().size());
   }
 
   public void testPackageJsonFile() {
     test(
-        srcs(SourceFile.fromCode("/package.json", "{ \"main\": \"foo/bar/baz.js\"}")),
+        srcs(SourceFile.fromCode("/package.json", "{ 'main': 'foo/bar/baz.js'}")),
         expected(lines(
             "goog.provide('module$package_json')",
-            "var module$package_json = {\"main\": \"foo/bar/baz.js\"};")));
+            "var module$package_json = {'main': 'foo/bar/baz.js'};")));
 
     assertEquals(1, getLastCompiler().getModuleLoader().getPackageJsonMainEntries().size());
     assert (getLastCompiler()
@@ -74,11 +77,30 @@ public void testPackageJsonFile() {
 
   public void testPackageJsonWithoutMain() {
     test(
-        srcs(SourceFile.fromCode("/package.json", "{\"other\": { \"main\": \"foo/bar/baz.js\"}}")),
+        srcs(SourceFile.fromCode("/package.json", "{'other': { 'main': 'foo/bar/baz.js'}}")),
         expected(lines(
             "goog.provide('module$package_json')",
-            "var module$package_json = {\"other\": { \"main\": \"foo/bar/baz.js\"}};")));
+            "var module$package_json = {'other': { 'main': 'foo/bar/baz.js'}};")));
 
     assertEquals(0, getLastCompiler().getModuleLoader().getPackageJsonMainEntries().size());
   }
+
+  public void testPackageJsonFileBrowserField() {
+    test(
+        srcs(
+            SourceFile.fromCode(
+                "/package.json",
+                "{ 'main': 'foo/bar/baz.js', 'browser': 'browser/foo.js' }")),
+        expected(
+            lines(
+                "goog.provide('module$package_json')",
+                "var module$package_json = {",
+                "  'main': 'foo/bar/baz.js',",
+                "  'browser': 'browser/foo.js'",
+                "};")));
+
+    assertThat(getLastCompiler().getModuleLoader().getPackageJsonMainEntries()).hasSize(1);
+    assertThat(getLastCompiler().getModuleLoader().getPackageJsonMainEntries())
+        .containsEntry("/package.json", "/browser/foo.js");
+  }
 }