Allow comment only JSONC files (#17269)

changelog_unreleased/json/17269.md

@@ -0,0 +1,15 @@
+#### Allow format comment-only JSONC files (#17269 by @fisker)
+
+<!-- prettier-ignore -->
+```jsonc
+// Input
+// Comment
+
+// Prettier stable
+SyntaxError: Unexpected token (1:11)
+> 1 | // Comment
+    |           ^
+
+// Prettier main
+// Comment
+```

src/language-js/print/estree.js

@@ -101,7 +101,7 @@ function printEstree(path, options, print, args) {
     case "JsExpressionRoot":
       return print("node");
     case "JsonRoot":
-      return [print("node"), hardline];
+      return [printDanglingComments(path, options), print("node"), hardline];
     case "File":
       return printHtmlBinding(path, options, print) ?? print("program");
     // Babel extension.

src/language-json/parser-json.js

@@ -1,35 +1,76 @@
-import { parseExpression } from "@babel/parser";
+import { parse, parseExpression } from "@babel/parser";
 import createError from "../common/parser-create-error.js";
 import createBabelParseError from "../language-js/parse/utils/create-babel-parse-error.js";
 import createParser from "../language-js/parse/utils/create-parser.js";
 import wrapBabelExpression from "../language-js/parse/utils/wrap-babel-expression.js";
 import isNonEmptyArray from "../utils/is-non-empty-array.js";
 
-function createJsonParse(options = {}) {
-  const { allowComments = true } = options;
+const babelParseOptions = {
+  tokens: true,
+  ranges: true,
+  attachComment: false,
+};
 
-  return function parse(text) {
-    let ast;
-    try {
-      ast = parseExpression(text, {
-        tokens: true,
-        ranges: true,
-        attachComment: false,
-      });
-    } catch (/** @type {any} */ error) {
+function parseEmptyJson(text) {
+  const file = parse(text, babelParseOptions);
+
+  const { program } = file;
+
+  // Not an empty JSON
+  /* c8 ignore next */
+  if (
+    !(
+      program.body.length === 0 &&
+      program.directives.length === 0 &&
+      !program.interpreter
+    )
+  ) {
+    return;
+  }
+
+  return file;
+}
+
+function parseJson(text, options = {}) {
+  const { allowComments = true, allowEmpty = false } = options;
+
+  let ast;
+  try {
+    ast = parseExpression(text, babelParseOptions);
+  } catch (/** @type {any} */ error) {
+    if (
+      allowEmpty &&
+      error.code === "BABEL_PARSER_SYNTAX_ERROR" &&
+      error.reasonCode === "UnexpectedToken" &&
+      error.pos === text.length
+    ) {
+      try {
+        ast = parseEmptyJson(text);
+      } catch {
+        // No op
+      }
+    }
+
+    if (!ast) {
       throw createBabelParseError(error);
     }
+  }
 
+  // @ts-expect-error
+  if (!allowComments && isNonEmptyArray(ast.comments)) {
     // @ts-expect-error
-    if (!allowComments && isNonEmptyArray(ast.comments)) {
-      // @ts-expect-error
-      throw createJsonError(ast.comments[0], "Comment");
-    }
+    throw createJsonError(ast.comments[0], "Comment");
+  }
 
-    assertJsonNode(ast);
+  ast = wrapBabelExpression(ast, { type: "JsonRoot", text });
 
-    return wrapBabelExpression(ast, { type: "JsonRoot", text });
-  };
+  if (ast.node.type === "File") {
+    delete ast.node;
+  } else {
+    assertJsonNode(ast.node);
+  }
+
+  return ast;
 }
 
 function createJsonError(node, description) {
@@ -131,19 +172,15 @@ function assertJsonNode(node) {
   }
 }
 
-const parseJson = createJsonParse();
-
 const jsonParsers = {
   json: createParser({
-    parse: parseJson,
-    hasPragma() {
-      return true;
-    },
+    parse: (text) => parseJson(text),
+    hasPragma: () => true,
   }),
-  json5: createParser(parseJson),
-  jsonc: createParser(parseJson),
+  json5: createParser((text) => parseJson(text)),
+  jsonc: createParser((text) => parseJson(text, { allowEmpty: true })),
   "json-stringify": createParser({
-    parse: createJsonParse({ allowComments: false }),
+    parse: (text) => parseJson(text, { allowComments: false }),
     astFormat: "estree-json",
   }),
 };

src/main/comments/attach.js

@@ -193,7 +193,7 @@ function attachComments(ast, options) {
         addLeadingComment(ast, comment);
         continue;
       }
-      if (locEnd(comment) - locEnd(ast) >= 0) {
+      if (locEnd(comment) > locEnd(ast)) {
         addTrailingComment(ast, comment);
         continue;
       }

tests/format/json/jsonc/empty/__snapshots__/format.test.js.snap

@@ -0,0 +1,47 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`snippet: #0 [json] format 1`] = `
+"Unexpected token (4:29)
+  2 |     /** Block comment 1 */
+  3 |     // Line comment 2
+> 4 |       /** Block comment 3 */
+    |                             ^
+Cause: Unexpected token (4:28)"
+`;
+
+exports[`snippet: #0 [json-stringify] format 1`] = `
+"Unexpected token (4:29)
+  2 |     /** Block comment 1 */
+  3 |     // Line comment 2
+> 4 |       /** Block comment 3 */
+    |                             ^
+Cause: Unexpected token (4:28)"
+`;
+
+exports[`snippet: #0 [json5] format 1`] = `
+"Unexpected token (4:29)
+  2 |     /** Block comment 1 */
+  3 |     // Line comment 2
+> 4 |       /** Block comment 3 */
+    |                             ^
+Cause: Unexpected token (4:28)"
+`;
+
+exports[`snippet: #0 format 1`] = `
+====================================options=====================================
+parsers: ["jsonc", "json", "json5", "json-stringify"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+// Line comment 1
+    /** Block comment 1 */
+    // Line comment 2
+      /** Block comment 3 */
+=====================================output=====================================
+// Line comment 1
+/** Block comment 1 */
+// Line comment 2
+/** Block comment 3 */
+
+================================================================================
+`;

tests/format/json/jsonc/empty/format.test.js

@@ -0,0 +1,25 @@
+import { outdent } from "outdent";
+
+runFormatTest(
+  {
+    importMeta: import.meta,
+    snippets: [
+      // "// Only line comment",
+      // "/* Only block comment */",
+      outdent`
+        // Line comment 1
+            /** Block comment 1 */
+            // Line comment 2
+              /** Block comment 3 */
+      `,
+    ],
+  },
+  ["jsonc", "json", "json5", "json-stringify"],
+  {
+    errors: {
+      json: true,
+      json5: true,
+      "json-stringify": true,
+    },
+  },
+);

tests/format/misc/errors/json/__snapshots__/format.test.js.snap

@@ -13,18 +13,46 @@ exports[`snippet: #0 [json] format 2`] = `
 Cause: A 'set' accessor must have exactly one formal parameter. (1:8)"
 `;
 
+exports[`snippet: #0 [json] format 3`] = `
+"Unexpected token (1:2)
+> 1 | [
+    |  ^
+Cause: Unexpected token (1:1)"
+`;
+
 exports[`snippet: #0 [json-stringify] format 1`] = `
 "Shorthand property is not allowed in JSON. (1:2)
 > 1 | {foo}
     |  ^^^"
 `;
 
+exports[`snippet: #0 [json-stringify] format 2`] = `
+"Unexpected token (1:2)
+> 1 | [
+    |  ^
+Cause: Unexpected token (1:1)"
+`;
+
 exports[`snippet: #0 [json5] format 1`] = `
 "Shorthand property is not allowed in JSON. (1:2)
 > 1 | {foo}
     |  ^^^"
 `;
 
+exports[`snippet: #0 [json5] format 2`] = `
+"Unexpected token (1:2)
+> 1 | [
+    |  ^
+Cause: Unexpected token (1:1)"
+`;
+
+exports[`snippet: #0 [jsonc] format 1`] = `
+"Unexpected token (1:2)
+> 1 | [
+    |  ^
+Cause: Unexpected token (1:1)"
+`;
+
 exports[`snippet: #1 [json] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {["foo"]:"bar"}
@@ -38,18 +66,46 @@ exports[`snippet: #1 [json] format 2`] = `
 Cause: Private name #bar is not defined. (1:20)"
 `;
 
+exports[`snippet: #1 [json] format 3`] = `
+"Unexpected token (1:1)
+> 1 | ;
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #1 [json-stringify] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {["foo"]:"bar"}
     |   ^^^^^"
 `;
 
+exports[`snippet: #1 [json-stringify] format 2`] = `
+"Unexpected token (1:1)
+> 1 | ;
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #1 [json5] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {["foo"]:"bar"}
     |   ^^^^^"
 `;
 
+exports[`snippet: #1 [json5] format 2`] = `
+"Unexpected token (1:1)
+> 1 | ;
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
+exports[`snippet: #1 [jsonc] format 1`] = `
+"Unexpected token (1:1)
+> 1 | ;
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #2 [json] format 1`] = `
 "Operator '~' is not allowed in JSON. (1:9)
 > 1 | {"foo": ~1}
@@ -63,18 +119,46 @@ exports[`snippet: #2 [json] format 2`] = `
 Cause: 'await' is only allowed within async functions and at the top levels of modules. (1:13)"
 `;
 
+exports[`snippet: #2 [json] format 3`] = `
+"Unexpected token (1:9)
+> 1 | "string";
+    |         ^
+Cause: Unexpected token (1:8)"
+`;
+
 exports[`snippet: #2 [json-stringify] format 1`] = `
 "Operator '~' is not allowed in JSON. (1:9)
 > 1 | {"foo": ~1}
     |         ^^"
 `;
 
+exports[`snippet: #2 [json-stringify] format 2`] = `
+"Unexpected token (1:9)
+> 1 | "string";
+    |         ^
+Cause: Unexpected token (1:8)"
+`;
+
 exports[`snippet: #2 [json5] format 1`] = `
 "Operator '~' is not allowed in JSON. (1:9)
 > 1 | {"foo": ~1}
     |         ^^"
 `;
 
+exports[`snippet: #2 [json5] format 2`] = `
+"Unexpected token (1:9)
+> 1 | "string";
+    |         ^
+Cause: Unexpected token (1:8)"
+`;
+
+exports[`snippet: #2 [jsonc] format 1`] = `
+"Unexpected token (1:9)
+> 1 | "string";
+    |         ^
+Cause: Unexpected token (1:8)"
+`;
+
 exports[`snippet: #3 [json] format 1`] = `
 "'LogicalExpression' is not allowed in JSON. (1:9)
 > 1 | {"foo": false || "bar"}
@@ -87,18 +171,50 @@ exports[`snippet: #3 [json] format 2`] = `
     |  ^"
 `;
 
+exports[`snippet: #3 [json] format 3`] = `
+"Unexpected token (2:1)
+  1 | "string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
 exports[`snippet: #3 [json-stringify] format 1`] = `
 "'LogicalExpression' is not allowed in JSON. (1:9)
 > 1 | {"foo": false || "bar"}
     |         ^^^^^^^^^^^^^^"
 `;
 
+exports[`snippet: #3 [json-stringify] format 2`] = `
+"Unexpected token (2:1)
+  1 | "string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
 exports[`snippet: #3 [json5] format 1`] = `
 "'LogicalExpression' is not allowed in JSON. (1:9)
 > 1 | {"foo": false || "bar"}
     |         ^^^^^^^^^^^^^^"
 `;
 
+exports[`snippet: #3 [json5] format 2`] = `
+"Unexpected token (2:1)
+  1 | "string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
+exports[`snippet: #3 [jsonc] format 1`] = `
+"Unexpected token (2:1)
+  1 | "string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
 exports[`snippet: #4 [json] format 1`] = `
 "'ArrowFunctionExpression' is not allowed in JSON. (1:9)
 > 1 | {"foo": () => {}}
@@ -112,18 +228,46 @@ exports[`snippet: #4 [json] format 2`] = `
 Cause: 'import' and 'export' may only appear at the top level. (1:13)"
 `;
 
+exports[`snippet: #4 [json] format 3`] = `
+"Unexpected token (1:15)
+> 1 | /* comment */[
+    |               ^
+Cause: Unexpected token (1:14)"
+`;
+
 exports[`snippet: #4 [json-stringify] format 1`] = `
 "'ArrowFunctionExpression' is not allowed in JSON. (1:9)
 > 1 | {"foo": () => {}}
     |         ^^^^^^^^"
 `;
 
+exports[`snippet: #4 [json-stringify] format 2`] = `
+"Unexpected token (1:15)
+> 1 | /* comment */[
+    |               ^
+Cause: Unexpected token (1:14)"
+`;
+
 exports[`snippet: #4 [json5] format 1`] = `
 "'ArrowFunctionExpression' is not allowed in JSON. (1:9)
 > 1 | {"foo": () => {}}
     |         ^^^^^^^^"
 `;
 
+exports[`snippet: #4 [json5] format 2`] = `
+"Unexpected token (1:15)
+> 1 | /* comment */[
+    |               ^
+Cause: Unexpected token (1:14)"
+`;
+
+exports[`snippet: #4 [jsonc] format 1`] = `
+"Unexpected token (1:15)
+> 1 | /* comment */[
+    |               ^
+Cause: Unexpected token (1:14)"
+`;
+
 exports[`snippet: #5 [json] format 1`] = `
 "Expecting Unicode escape sequence \\uXXXX. (1:10)
 > 1 | packages\\the-hub\\cypress\\fixtures\\gridConfiguration.json
@@ -138,6 +282,13 @@ exports[`snippet: #5 [json] format 2`] = `
 Cause: Unexpected token (1:0)"
 `;
 
+exports[`snippet: #5 [json] format 3`] = `
+"Unexpected token (1:14)
+> 1 | /* comment */;
+    |              ^
+Cause: Unexpected token (1:13)"
+`;
+
 exports[`snippet: #5 [json-stringify] format 1`] = `
 "Expecting Unicode escape sequence \\uXXXX. (1:10)
 > 1 | packages\\the-hub\\cypress\\fixtures\\gridConfiguration.json
@@ -145,6 +296,13 @@ exports[`snippet: #5 [json-stringify] format 1`] = `
 Cause: Expecting Unicode escape sequence \\uXXXX. (1:9)"
 `;
 
+exports[`snippet: #5 [json-stringify] format 2`] = `
+"Unexpected token (1:14)
+> 1 | /* comment */;
+    |              ^
+Cause: Unexpected token (1:13)"
+`;
+
 exports[`snippet: #5 [json5] format 1`] = `
 "Expecting Unicode escape sequence \\uXXXX. (1:10)
 > 1 | packages\\the-hub\\cypress\\fixtures\\gridConfiguration.json
@@ -152,6 +310,20 @@ exports[`snippet: #5 [json5] format 1`] = `
 Cause: Expecting Unicode escape sequence \\uXXXX. (1:9)"
 `;
 
+exports[`snippet: #5 [json5] format 2`] = `
+"Unexpected token (1:14)
+> 1 | /* comment */;
+    |              ^
+Cause: Unexpected token (1:13)"
+`;
+
+exports[`snippet: #5 [jsonc] format 1`] = `
+"Unexpected token (1:14)
+> 1 | /* comment */;
+    |              ^
+Cause: Unexpected token (1:13)"
+`;
+
 exports[`snippet: #6 [json] format 1`] = `
 "'BinaryExpression' is not allowed in JSON. (1:1)
 > 1 | 1+2
@@ -165,18 +337,46 @@ exports[`snippet: #6 [json] format 2`] = `
 Cause: Unexpected token, expected "," (1:2)"
 `;
 
+exports[`snippet: #6 [json] format 3`] = `
+"Unexpected token (1:22)
+> 1 | /* comment */"string";
+    |                      ^
+Cause: Unexpected token (1:21)"
+`;
+
 exports[`snippet: #6 [json-stringify] format 1`] = `
 "'BinaryExpression' is not allowed in JSON. (1:1)
 > 1 | 1+2
     | ^^^"
 `;
 
+exports[`snippet: #6 [json-stringify] format 2`] = `
+"Unexpected token (1:22)
+> 1 | /* comment */"string";
+    |                      ^
+Cause: Unexpected token (1:21)"
+`;
+
 exports[`snippet: #6 [json5] format 1`] = `
 "'BinaryExpression' is not allowed in JSON. (1:1)
 > 1 | 1+2
     | ^^^"
 `;
 
+exports[`snippet: #6 [json5] format 2`] = `
+"Unexpected token (1:22)
+> 1 | /* comment */"string";
+    |                      ^
+Cause: Unexpected token (1:21)"
+`;
+
+exports[`snippet: #6 [jsonc] format 1`] = `
+"Unexpected token (1:22)
+> 1 | /* comment */"string";
+    |                      ^
+Cause: Unexpected token (1:21)"
+`;
+
 exports[`snippet: #7 [json] format 1`] = `
 "Shorthand property is not allowed in JSON. (1:2)
 > 1 | {Infinity}
@@ -189,18 +389,50 @@ exports[`snippet: #7 [json] format 2`] = `
     |                        ^"
 `;
 
+exports[`snippet: #7 [json] format 3`] = `
+"Unexpected token (2:1)
+  1 | /* comment */"string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
 exports[`snippet: #7 [json-stringify] format 1`] = `
 "Shorthand property is not allowed in JSON. (1:2)
 > 1 | {Infinity}
     |  ^^^^^^^^"
 `;
 
+exports[`snippet: #7 [json-stringify] format 2`] = `
+"Unexpected token (2:1)
+  1 | /* comment */"string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
 exports[`snippet: #7 [json5] format 1`] = `
 "Shorthand property is not allowed in JSON. (1:2)
 > 1 | {Infinity}
     |  ^^^^^^^^"
 `;
 
+exports[`snippet: #7 [json5] format 2`] = `
+"Unexpected token (2:1)
+  1 | /* comment */"string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
+exports[`snippet: #7 [jsonc] format 1`] = `
+"Unexpected token (2:1)
+  1 | /* comment */"string"
+> 2 | ;
+    | ^
+Cause: Unexpected token (2:0)"
+`;
+
 exports[`snippet: #8 [json] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {[key]: 1}
@@ -213,18 +445,46 @@ exports[`snippet: #8 [json] format 2`] = `
     |  ^"
 `;
 
+exports[`snippet: #8 [json] format 3`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #8 [json-stringify] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {[key]: 1}
     |   ^^^"
 `;
 
+exports[`snippet: #8 [json-stringify] format 2`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #8 [json5] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {[key]: 1}
     |   ^^^"
 `;
 
+exports[`snippet: #8 [json5] format 2`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
+exports[`snippet: #8 [jsonc] format 1`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #9 [json] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {[key()]: 1}
@@ -237,18 +497,50 @@ exports[`snippet: #9 [json] format 2`] = `
     |      ^"
 `;
 
+exports[`snippet: #9 [json] format 3`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+  2 | []
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #9 [json-stringify] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {[key()]: 1}
     |   ^^^^^"
 `;
 
+exports[`snippet: #9 [json-stringify] format 2`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+  2 | []
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #9 [json5] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {[key()]: 1}
     |   ^^^^^"
 `;
 
+exports[`snippet: #9 [json5] format 2`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+  2 | []
+Cause: Unexpected token (1:0)"
+`;
+
+exports[`snippet: #9 [jsonc] format 1`] = `
+"Unexpected token (1:1)
+> 1 | #!/usr/bin/env node
+    | ^
+  2 | []
+Cause: Unexpected token (1:0)"
+`;
+
 exports[`snippet: #10 [json] format 1`] = `
 "Computed key is not allowed in JSON. (1:3)
 > 1 | {['CallExpression']: 1}

tests/format/misc/errors/json/format.test.js

@@ -101,3 +101,22 @@ runFormatTest(
   },
   ["json"],
 );
+
+runFormatTest(
+  {
+    importMeta: import.meta,
+    snippets: [
+      "[",
+      ";",
+      '"string";',
+      '"string"\n;',
+      "/* comment */[",
+      "/* comment */;",
+      '/* comment */"string";',
+      '/* comment */"string"\n;',
+      "#!/usr/bin/env node",
+      "#!/usr/bin/env node\n[]",
+    ],
+  },
+  ["json", "json5", "jsonc", "json-stringify"],
+);