Add test case for custom rule that imports an ESM module (refs #477).

test/markdownlint-test-custom-rules.js

@@ -1143,6 +1143,32 @@ test.cb("customRulesLintJavaScript", (t) => {
   });
 });
 
+test.cb("customRulesValidateJson", (t) => {
+  t.plan(2);
+  const options = {
+    "customRules": customRules.validateJson,
+    "files": "test/validate-json.md"
+  };
+  markdownlint(options, (err, actual) => {
+    t.falsy(err);
+    const expected = {
+      "test/validate-json.md": [
+        {
+          "lineNumber": 22,
+          "ruleNames": [ "validate-json" ],
+          "ruleDescription": "Rule that validates JSON code",
+          "ruleInformation": null,
+          "errorDetail": "Unexpected end of JSON input",
+          "errorContext": null,
+          "errorRange": null
+        }
+      ]
+    };
+    t.deepEqual(actual, expected, "Unexpected issues.");
+    t.end();
+  });
+});
+
 test("customRulesAsyncThrowsInSyncContext", (t) => {
   t.plan(1);
   const options = {

test/markdownlint-test.js

@@ -1109,7 +1109,7 @@ test("allBuiltInRulesHaveValidUrl", (t) => {
 });
 
 test("someCustomRulesHaveValidUrl", (t) => {
-  t.plan(7);
+  t.plan(8);
   customRules.all.forEach(function forRule(rule) {
     t.true(!rule.information ||
       (Object.getPrototypeOf(rule.information) === URL.prototype));

test/rules/rules.js

@@ -17,10 +17,14 @@ module.exports.lettersEX = lettersEX;
 const lintJavaScript = require("./lint-javascript");
 module.exports.lintJavaScript = lintJavaScript;
 
+const validateJson = require("./validate-json");
+module.exports.validateJson = validateJson;
+
 module.exports.all = [
   anyBlockquote,
   everyNLines,
   firstLine,
   lettersEX,
-  lintJavaScript
+  lintJavaScript,
+  validateJson
 ];

test/rules/validate-json.js

@@ -0,0 +1,28 @@
+// @ts-check
+
+"use strict";
+
+const { filterTokens } = require("markdownlint-rule-helpers");
+
+module.exports = {
+  "names": [ "validate-json" ],
+  "description": "Rule that validates JSON code",
+  "tags": [ "test", "validate", "json" ],
+  "asynchronous": true,
+  "function": async(params, onError) => {
+    // eslint-disable-next-line max-len, node/no-unsupported-features/es-syntax
+    const { "default": stripJsonComments } = await import("strip-json-comments");
+    filterTokens(params, "fence", (fence) => {
+      if (/jsonc?/i.test(fence.info)) {
+        try {
+          JSON.parse(stripJsonComments(fence.content));
+        } catch (error) {
+          onError({
+            "lineNumber": fence.lineNumber,
+            "detail": error.message
+          });
+        }
+      }
+    });
+  }
+};

test/validate-json.md

@@ -0,0 +1,27 @@
+# Validate JSON
+
+Text
+
+```json
+{
+    "property": "value"
+}
+```
+
+Text
+
+```jsonc
+{
+    // Comment
+    "property": "value"
+}
+```
+
+Text
+
+```json
+{
+    "property": "value"
+```
+
+Text