Avoid using regex parser unless bundling or pruning unused inputs

This assumes all other kinds of compilations will need an actual AST for each input, and so regex parsing, while faster, is redundant.

PiperOrigin-RevId: 506075616

Author: lauraharker

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

@@ -487,6 +487,11 @@ protected void setRunOptions(CompilerOptions options) throws IOException {
     if (config.printTree || config.printTreeJson) {
       options.setParseJsDocDocumentation(Config.JsDocParsing.INCLUDE_ALL_COMMENTS);
     }
+    if (config.skipNormalOutputs) {
+      // If skipping normal outputs, it's unnecessary to do a full AST parse of each input file.
+      // The regex parser may still run if ordering/pruning inputs.
+      compiler.setPreferRegexParser(true);
+    }
   }
 
   @GwtIncompatible("Unnecessary")

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

@@ -421,6 +421,9 @@ public int size() {
       // description.
       options.setParseJsDocDocumentation(JsDocParsing.INCLUDE_ALL_COMMENTS);
     }
+    // If pruning many unused inputs, it's possible that it's faster to regex-parse everything and
+    // AST-parse only the non-pruned inputs, rather than just AST-parse everything once.
+    this.preferRegexParser = this.preferRegexParser || options.getDependencyOptions().shouldPrune();
   }
 
   public void printConfig() {
@@ -2001,8 +2004,7 @@ void setPreferRegexParser(boolean preferRegexParser) {
     this.preferRegexParser = preferRegexParser;
   }
 
-  // TODO(b/264916633): make this default to false.
-  private boolean preferRegexParser = true;
+  private boolean preferRegexParser = false;
 
   void orderInputsWithLargeStack() {
     runInCompilerThread(

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

@@ -2835,6 +2835,55 @@ public void testInstrumentCodeProductionArrayArgNotSet() {
                 + "--instrument_for_coverage_option is set to Production");
   }
 
+  @Test
+  public void testBundleOutput_bundlesGoogModule() throws IOException {
+    // Create a path for the final output
+    File bundledFile = temporaryFolder.newFile("bundle.js");
+
+    FlagEntry<JsSourceType> jsFile1 = createJsFile("test1", "var a;");
+    FlagEntry<JsSourceType> jsFile2 = createJsFile("test2", "goog.module('foo'); var b;");
+
+    args.add("--compilation_level=BUNDLE");
+    args.add("--dependency_mode=NONE");
+    args.add("--js_output_file");
+    args.add(bundledFile.getPath());
+
+    compileJsFiles("", jsFile1, jsFile2);
+
+    String bundledJs = java.nio.file.Files.readString(bundledFile.toPath());
+    String expected =
+        lines(
+            "//" + jsFile1.getValue(),
+            "var a;",
+            "//" + jsFile2.getValue(),
+            "goog.loadModule(function(exports) {'use strict';goog.module('foo'); var b;",
+            ";return exports;});",
+            "\n");
+    assertThat(bundledJs).isEqualTo(expected);
+  }
+
+  @Test
+  public void testBundleOutput_ignoresSyntaxErrors() throws IOException {
+    // Verify that if bundling, the compiler doesn't run a full parse and thus doesn't report
+    // syntax errors.
+
+    // Create a path for the final output
+    File bundledFile = temporaryFolder.newFile("bundle.js");
+
+    FlagEntry<JsSourceType> jsFile = createJsFile("test1", "var a; syntax error!");
+
+    args.add("--compilation_level=BUNDLE");
+    args.add("--dependency_mode=NONE");
+    args.add("--js_output_file");
+    args.add(bundledFile.getPath());
+
+    compileJsFiles("", jsFile);
+
+    String bundledJs = java.nio.file.Files.readString(bundledFile.toPath());
+    String expected = lines("//" + jsFile.getValue(), "var a; syntax error!\n");
+    assertThat(bundledJs).isEqualTo(expected);
+  }
+
   @Rule public TemporaryFolder folder = new TemporaryFolder();
 
   @Test
@@ -3278,6 +3327,7 @@ private void compileArgs(String expectedOutput, @Nullable DiagnosticType expecte
       assertThat(compiler.getErrors()).hasSize(1);
       assertError(compiler.getErrors().get(0)).hasType(expectedError);
     }
+    lastCommandLineRunner = runner;
   }
 
   private String compile(String inputString, List<String> args) {