JSON: Disallow sparse array (#10443)

changelog_unreleased/json/10346.md

@@ -1,4 +1,4 @@
-#### Stricter JSON parser (#10346 by @fisker)
+#### Stricter JSON parser (#10346, #10443 by @fisker)
 
 Previously we allow all kinds of JavaScript expressions in `json` and `json5` parser, now they are stricter.
 

src/language-js/parser/json.js

@@ -35,6 +35,15 @@ function assertJsonNode(node, parent) {
   switch (node.type) {
     case "ArrayExpression":
       for (const element of node.elements) {
+        if (element === null) {
+          throw createError("Sparse array is not allowed in JSON.", {
+            start: {
+              line: node.loc.start.line,
+              column: node.loc.start.column + 1,
+            },
+          });
+        }
+
         assertJsonChildNode(element);
       }
       return;

tests/json/json/__snapshots__/jsfmt.spec.js.snap

@@ -1,5 +1,138 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`array.json - {"trailingComma":"all"} format 1`] = `
+====================================options=====================================
+parsers: ["json"]
+printWidth: 80
+trailingComma: "all"
+                                                                                | printWidth
+=====================================input======================================
+[
+  [
+1,null],
+  [1,null,],
+  [null,],
+  [0,],
+  [false,],
+  ['',]
+]
+
+=====================================output=====================================
+[[1, null], [1, null], [null], [0], [false], [""]]
+
+================================================================================
+`;
+
+exports[`array.json - {"trailingComma":"all"} format 2`] = `
+====================================options=====================================
+parsers: ["json5"]
+printWidth: 80
+trailingComma: "all"
+                                                                                | printWidth
+=====================================input======================================
+[
+  [
+1,null],
+  [1,null,],
+  [null,],
+  [0,],
+  [false,],
+  ['',]
+]
+
+=====================================output=====================================
+[[1, null], [1, null], [null], [0], [false], [""]]
+
+================================================================================
+`;
+
+exports[`array.json format 1`] = `
+====================================options=====================================
+parsers: ["json"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+[
+  [
+1,null],
+  [1,null,],
+  [null,],
+  [0,],
+  [false,],
+  ['',]
+]
+
+=====================================output=====================================
+[[1, null], [1, null], [null], [0], [false], [""]]
+
+================================================================================
+`;
+
+exports[`array.json format 2`] = `
+====================================options=====================================
+parsers: ["json5"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+[
+  [
+1,null],
+  [1,null,],
+  [null,],
+  [0,],
+  [false,],
+  ['',]
+]
+
+=====================================output=====================================
+[[1, null], [1, null], [null], [0], [false], [""]]
+
+================================================================================
+`;
+
+exports[`array.json format 3`] = `
+====================================options=====================================
+parsers: ["json-stringify"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+[
+  [
+1,null],
+  [1,null,],
+  [null,],
+  [0,],
+  [false,],
+  ['',]
+]
+
+=====================================output=====================================
+[
+  [
+    1,
+    null
+  ],
+  [
+    1,
+    null
+  ],
+  [
+    null
+  ],
+  [
+    0
+  ],
+  [
+    false
+  ],
+  [
+    ""
+  ]
+]
+
+================================================================================
+`;
+
 exports[`boolean.json - {"trailingComma":"all"} format 1`] = `
 ====================================options=====================================
 parsers: ["json"]

tests/json/json/array.json

@@ -0,0 +1,9 @@
+[
+  [
+1,null],
+  [1,null,],
+  [null,],
+  [0,],
+  [false,],
+  ['',]
+]

tests/misc/errors/json/__snapshots__/jsfmt.spec.js.snap

@@ -24,12 +24,24 @@ exports[`snippet: #1 [json-stringify] format 1`] = `
     |  ^"
 `;
 
+exports[`snippet: #2 [json] format 1`] = `
+"Sparse array is not allowed in JSON. (1:1)
+> 1 | [,]
+    | ^"
+`;
+
 exports[`snippet: #2 [json-stringify] format 1`] = `
 "UnaryExpression with operator=\\"~\\" is not allowed in JSON. (1:9)
 > 1 | {\\"foo\\": ~1}
     |         ^"
 `;
 
+exports[`snippet: #3 [json] format 1`] = `
+"Sparse array is not allowed in JSON. (1:1)
+> 1 | [1,,2]
+    | ^"
+`;
+
 exports[`snippet: #3 [json-stringify] format 1`] = `
 "LogicalExpression is not allowed in JSON. (1:9)
 > 1 | {\\"foo\\": false || \\"bar\\"}

tests/misc/errors/json/jsfmt.spec.js

@@ -21,6 +21,8 @@ run_spec(
     snippets: [
       "packages\\the-hub\\cypress\\fixtures\\gridConfiguration.json",
       "1+2",
+      "[,]",
+      "[1,,2]",
     ],
   },
   ["json"]