JS: Use JSX syntax in first attempt when extension is .jsx

javascript/extractor/src/com/semmle/js/extractor/JSExtractor.java

@@ -56,8 +56,10 @@ public Pair<Label, ParseResultInfo> extract(
 
     SourceType sourceType = establishSourceType(source, true);
 
+    String extension = textualExtractor.getLocationManager().getSourceFileExtension();
+
     JSParser.Result parserRes =
-        JSParser.parse(config, sourceType, source, textualExtractor.getMetrics());
+        JSParser.parse(config, sourceType, extension, source, textualExtractor.getMetrics());
 
     // Check if we guessed wrong with the regex in `establishSourceType`, (which could
     // happen due to a block-comment line starting with '  import').
@@ -74,7 +76,7 @@ public Pair<Label, ParseResultInfo> extract(
       if (wrongGuess) {
         sourceType = SourceType.SCRIPT;
         parserRes =
-          JSParser.parse(config, sourceType, source, textualExtractor.getMetrics());
+          JSParser.parse(config, sourceType, extension, source, textualExtractor.getMetrics());
       }
     }
 

javascript/extractor/src/com/semmle/js/parser/JSParser.java

@@ -68,9 +68,9 @@ public List<ParseError> getErrors() {
   }
 
   public static Result parse(
-      ExtractorConfig config, SourceType sourceType, String source, ExtractionMetrics metrics) {
+      ExtractorConfig config, SourceType sourceType, String extension, String source, ExtractionMetrics metrics) {
     metrics.startPhase(ExtractionPhase.JSParser_parse);
-    Result result = JcornWrapper.parse(config, sourceType, source);
+    Result result = JcornWrapper.parse(config, sourceType, extension, source);
     metrics.stopPhase(ExtractionPhase.JSParser_parse);
     return result;
   }

javascript/extractor/src/com/semmle/js/parser/JcornWrapper.java

@@ -14,9 +14,14 @@
 import com.semmle.js.extractor.ExtractorConfig.SourceType;
 
 public class JcornWrapper {
+  public static boolean alwaysParseWithJsx(String extension) {
+    // Note that .tsx is not relevant here since this is specifically for the JS parser.
+    return extension.equals(".jsx");
+  }
+
   /** Parse source code as a program. */
   public static JSParser.Result parse(
-      ExtractorConfig config, SourceType sourceType, String source) {
+      ExtractorConfig config, SourceType sourceType, String extension, String source) {
     ECMAVersion ecmaVersion = config.getEcmaVersion();
     List<Comment> comments = new ArrayList<>();
     List<Token> tokens = new ArrayList<>();
@@ -32,7 +37,11 @@ public static JSParser.Result parse(
 
     Program program = null;
     List<ParseError> errors = new ArrayList<>();
-
+
+    // If the file extension implies JSX syntax, use that in the first parsing attempt.
+    // This enables us to parse JSX files that the Flow parser cannot handle due to ambiguous syntax.
+    if (alwaysParseWithJsx(extension)) options = new JSXOptions(options);
+
     try {
       try {
         // First try to parse as a regular JavaScript program.

javascript/extractor/test/com/semmle/js/extractor/test/ES2015DetectorTests.java

@@ -16,7 +16,7 @@ public class ES2015DetectorTests {
   private static final ExtractorConfig CONFIG = new ExtractorConfig(true);
 
   private void isES2015(String src, boolean expected) {
-    Result res = JSParser.parse(CONFIG, SourceType.MODULE, src, new ExtractionMetrics());
+    Result res = JSParser.parse(CONFIG, SourceType.MODULE, ".jsx", src, new ExtractionMetrics());
     Node ast = res.getAST();
     Assert.assertNotNull(ast);
     Assert.assertTrue(ES2015Detector.looksLikeES2015(ast) == expected);

javascript/extractor/test/com/semmle/js/extractor/test/NodeJSDetectorTests.java

@@ -16,7 +16,7 @@ public class NodeJSDetectorTests {
   private static final ExtractorConfig CONFIG = new ExtractorConfig(true);
 
   private void isNodeJS(String src, boolean expected) {
-    Result res = JSParser.parse(CONFIG, SourceType.SCRIPT, src, new ExtractionMetrics());
+    Result res = JSParser.parse(CONFIG, SourceType.SCRIPT, ".jsx", src, new ExtractionMetrics());
     Node ast = res.getAST();
     Assert.assertNotNull(ast);
     Assert.assertTrue(NodeJSDetector.looksLikeNodeJS(ast) == expected);

javascript/extractor/tests/jsx/input/repro1.jsx

@@ -0,0 +1,4 @@
+function foo() {
+    let x = <div></div>;
+    return true ? (null, null) : e => { };
+}