Add comprehensive tests for parseConfiguration function, handle non-object parser results consistently (fixes #1523).

lib/markdownlint.mjs

@@ -1183,6 +1183,7 @@ export function readConfigSync(file, parsers, fs) {
   // Try to parse file
   const { config, message } = parseConfiguration(file, content, parsers);
   if (!config) {
+    // @ts-ignore
     throw new Error(message);
   }
   // Extend configuration

lib/parse-configuration.mjs

@@ -5,7 +5,7 @@
  *
  * @typedef {Object} ParseConfigurationResult
  * @property {Object | null} config Configuration object if successful.
- * @property {string} message Error message if an error occurred.
+ * @property {string | null} message Error message if an error occurred.
  */
 
 /**
@@ -18,20 +18,24 @@
  */
 export default function parseConfiguration(name, content, parsers) {
   let config = null;
-  let message = "";
+  let message = null;
   const errors = [];
   let index = 0;
   // Try each parser
-  (parsers || [ JSON.parse ]).every((parser) => {
+  const failed = (parsers || [ JSON.parse ]).every((parser) => {
     try {
-      config = parser(content);
+      const result = parser(content);
+      config = (result && (typeof result === "object") && !Array.isArray(result)) ? result : {};
+      // Succeeded
+      return false;
     } catch (error) {
       errors.push(`Parser ${index++}: ${error.message}`);
     }
-    return !config;
+    // Failed, try the next parser
+    return true;
   });
   // Message if unable to parse
-  if (!config) {
+  if (failed) {
     errors.unshift(`Unable to parse '${name}'`);
     message = errors.join("; ");
   }

test/markdownlint-test.mjs

@@ -1305,7 +1305,6 @@ test("configParsersTOML", async(t) => {
       ].join("\n")
     },
     "configParsers": [
-      jsoncParser.parse,
       require("toml").parse
     ]
   };

test/parse-configuration-test.mjs

@@ -13,12 +13,94 @@ const testObject = {
 };
 const successfulTestObjectResult = {
   "config": testObject,
-  "message": ""
+  "message": null
+};
+const successfulParser = () => testObject;
+const failingParser = () => {
+  throw new Error("failingParser");
 };
-const testObjectJsonString = JSON.stringify(testObject);
 
-test("json object, default parsers", (t) => {
+test("json object, default parser", (t) => {
   t.plan(1);
-  const actual = parseConfiguration("name", testObjectJsonString);
+  const actual = parseConfiguration("name", JSON.stringify(testObject));
   t.deepEqual(actual, successfulTestObjectResult);
 });
+
+test("invalid json, default parser", (t) => {
+  t.plan(1);
+  const actual = parseConfiguration("name", "{");
+  const expected = {
+    "config": null,
+    "message": "Unable to parse 'name'; Parser 0: Expected property name or '}' in JSON at position 1 (line 1 column 2)"
+  };
+  t.deepEqual(actual, expected);
+});
+
+test("parser gets passed content", (t) => {
+  t.plan(2);
+  const content = "content";
+  const parser = (text) => {
+    t.is(text, content);
+    return {};
+  };
+  const actual = parseConfiguration("name", content, [ parser ]);
+  const expected = {
+    "config": {},
+    "message": null
+  };
+  t.deepEqual(actual, expected);
+});
+
+test("parser returns undefined/null/number/string/array", (t) => {
+  t.plan(5);
+  const expected = {
+    "config": {},
+    "message": null
+  };
+  const testCases = [ undefined, null, 10, "string", [] ];
+  for (const testCase of testCases) {
+    /** @type {import("../lib/markdownlint.mjs").ConfigurationParser} */
+    const parser =
+      // @ts-ignore
+      () => testCase;
+    const actual = parseConfiguration("name", "content", [ parser ]);
+    t.deepEqual(actual, expected);
+  }
+});
+
+test("custom parsers, successful/failing", (t) => {
+  t.plan(1);
+  const actual = parseConfiguration("name", "", [ successfulParser, failingParser ]);
+  t.deepEqual(actual, successfulTestObjectResult);
+});
+
+test("custom parsers, failing/successful", (t) => {
+  t.plan(1);
+  const actual = parseConfiguration("name", "", [ failingParser, successfulParser ]);
+  t.deepEqual(actual, successfulTestObjectResult);
+});
+
+test("custom parsers, failing/successful(undefined)", (t) => {
+  t.plan(1);
+  const actual = parseConfiguration(
+    "name",
+    "",
+    // @ts-ignore
+    [ failingParser, () => undefined ]
+  );
+  const expected = {
+    "config": {},
+    "message": null
+  };
+  t.deepEqual(actual, expected);
+});
+
+test("custom parsers, failing/failing", (t) => {
+  t.plan(1);
+  const actual = parseConfiguration("name", "", [ failingParser, failingParser ]);
+  const expected = {
+    "config": null,
+    "message": "Unable to parse 'name'; Parser 0: failingParser; Parser 1: failingParser"
+  };
+  t.deepEqual(actual, expected);
+});