Merge pull request #19267 from asgerf/js/json-array-trailing-comma

JS: Tolerate trailing commas in JSON arrays

Author: asgerf

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

@@ -42,7 +42,7 @@ public class Main {
    * A version identifier that should be updated every time the extractor changes in such a way that
    * it may produce different tuples for the same file under the same {@link ExtractorConfig}.
    */
-  public static final String EXTRACTOR_VERSION = "2025-03-20";
+  public static final String EXTRACTOR_VERSION = "2025-04-10";
 
   public static final Pattern NEWLINE = Pattern.compile("\n");
 

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

@@ -205,9 +205,6 @@ private JSONArray readArray(int startoff, Position start) throws ParseError {
         char c = peek();
         switch (c) {
           case ']':
-            if (!needsComma) {
-              raise("Omitted elements are not allowed in JSON.");
-            }
             next();
             break out;
           case ',':

javascript/extractor/tests/json/input/array-trailing-comma.json

@@ -0,0 +1,6 @@
+{
+    "array": [
+        "foo",
+        "bar",
+    ]
+}

javascript/extractor/tests/json/output/trap/array-trailing-comma.json.trap

@@ -0,0 +1,33 @@
+#10000=@"/array-trailing-comma.json;sourcefile"
+files(#10000,"/array-trailing-comma.json")
+#10001=@"/;folder"
+folders(#10001,"/")
+containerparent(#10001,#10000)
+#10002=@"loc,{#10000},0,0,0,0"
+locations_default(#10002,#10000,0,0,0,0)
+hasLocation(#10000,#10002)
+#20000=*
+json(#20000,5,#10000,0,"{\n    "" ...     ]\n}")
+#20001=@"loc,{#10000},1,1,6,1"
+locations_default(#20001,#10000,1,1,6,1)
+json_locations(#20000,#20001)
+#20002=*
+json(#20002,4,#20000,0,"[\n      ... ,\n    ]")
+#20003=@"loc,{#10000},2,14,5,5"
+locations_default(#20003,#10000,2,14,5,5)
+json_locations(#20002,#20003)
+#20004=*
+json(#20004,3,#20002,0,"""foo""")
+#20005=@"loc,{#10000},3,9,3,13"
+locations_default(#20005,#10000,3,9,3,13)
+json_locations(#20004,#20005)
+json_literals("foo","""foo""",#20004)
+#20006=*
+json(#20006,3,#20002,1,"""bar""")
+#20007=@"loc,{#10000},4,9,4,13"
+locations_default(#20007,#10000,4,9,4,13)
+json_locations(#20006,#20007)
+json_literals("bar","""bar""",#20006)
+json_properties(#20000,"array",#20002)
+numlines(#10000,6,0,0)
+filetype(#10000,"json")

javascript/ql/src/change-notes/2025-04-10-json-array-trailing-comma.md

@@ -0,0 +1,4 @@
+---
+category: fix
+---
+* Fixed a bug that would prevent extraction of `tsconfig.json` files when it contained an array literal with a trailing comma.