Create strict JSON Schema for configuration (standalone for ease of use) and corresponding strict TypeScript type (via extends for conciseness) (fixes #1248).

demo/markdownlint-browser.js

@@ -3140,6 +3140,13 @@ module.exports = markdownlint;
  * @typedef {import("./configuration").Configuration} Configuration
  */
 
+/**
+ * Configuration object for linting rules strictly. For the JSON schema, see
+ * {@link ../schema/markdownlint-config-schema-strict.json}.
+ *
+ * @typedef {import("./configuration-strict").ConfigurationStrict} ConfigurationStrict
+ */
+
 /**
  * Rule configuration object.
  *

example/typescript/type-check.ts

@@ -164,3 +164,20 @@ markdownlint(options, assertLintResultsCallback);
 (async () => {
   assertLintResultsCallback(null, await markdownlint.promises.markdownlint(options));
 })();
+
+const configuration: markdownlint.Configuration = {
+  "custom-rule": true,
+  "no-hard-tabs": false,
+  "heading-style": {
+    "style": "consistent"
+  }
+};
+assert(configuration);
+const configurationStrict: markdownlint.ConfigurationStrict = {
+  // "custom-rule": true,
+  "no-hard-tabs": false,
+  "heading-style": {
+    "style": "consistent"
+  }
+};
+assert(configurationStrict);

lib/markdownlint.d.ts

@@ -8,7 +8,7 @@ export = markdownlint;
  */
 declare function markdownlint(options: Options | null, callback: LintCallback): void;
 declare namespace markdownlint {
-    export { markdownlintSync as sync, readConfig, readConfigSync, getVersion, promises, GetMarkdownIt, RuleFunction, RuleParams, MarkdownParsers, ParserMarkdownIt, ParserMicromark, MarkdownItToken, MicromarkTokenType, MicromarkToken, RuleOnError, RuleOnErrorInfo, RuleOnErrorFixInfo, Rule, Options, Plugin, ToStringCallback, LintResults, LintError, FixInfo, LintContentCallback, LintCallback, Configuration, RuleConfiguration, ConfigurationParser, ReadConfigCallback, ResolveConfigExtendsCallback };
+    export { markdownlintSync as sync, readConfig, readConfigSync, getVersion, promises, GetMarkdownIt, RuleFunction, RuleParams, MarkdownParsers, ParserMarkdownIt, ParserMicromark, MarkdownItToken, MicromarkTokenType, MicromarkToken, RuleOnError, RuleOnErrorInfo, RuleOnErrorFixInfo, Rule, Options, Plugin, ToStringCallback, LintResults, LintError, FixInfo, LintContentCallback, LintCallback, Configuration, ConfigurationStrict, RuleConfiguration, ConfigurationParser, ReadConfigCallback, ResolveConfigExtendsCallback };
 }
 /**
  * Lint specified Markdown files synchronously.
@@ -439,6 +439,11 @@ type LintCallback = (error: Error | null, results?: LintResults) => void;
  * {@link  ../schema/markdownlint-config-schema.json}.
  */
 type Configuration = import("./configuration").Configuration;
+/**
+ * Configuration object for linting rules strictly. For the JSON schema, see
+ * {@link  ../schema/markdownlint-config-schema-strict.json}.
+ */
+type ConfigurationStrict = import("./configuration-strict").ConfigurationStrict;
 /**
  * Rule configuration.
  */

lib/markdownlint.js

@@ -1532,6 +1532,13 @@ module.exports = markdownlint;
  * @typedef {import("./configuration").Configuration} Configuration
  */
 
+/**
+ * Configuration object for linting rules strictly. For the JSON schema, see
+ * {@link ../schema/markdownlint-config-schema-strict.json}.
+ *
+ * @typedef {import("./configuration-strict").ConfigurationStrict} ConfigurationStrict
+ */
+
 /**
  * Rule configuration object.
  *

schema/ValidatingConfiguration.md

@@ -1,7 +1,7 @@
 # Validating Configuration
 
 A [JSON Schema][json-schema] is provided to enable validating configuration
-objects: [`markdownlint-config-schema.json`][markdownlint-config-schema]
+objects: [`markdownlint-config-schema.json`][markdownlint-config-schema].
 
 Some editors automatically use a JSON Schema with files that reference it. For
 example, a `.markdownlint.json` file with:
@@ -16,13 +16,11 @@ A JSON Schema validator can be used to check configuration files like so:
 npx ajv-cli validate -s ./markdownlint/schema/markdownlint-config-schema.json -d "**/.markdownlint.{json,yaml}" --strict=false
 ```
 
-By default, any rule name is valid in order to allow for custom rules. To ensure
-that only built-in rules are used, change the value of `#/additionalProperties`
-(at the bottom of the schema file) to `false` before validating:
-
-```json
-"additionalProperties": false
-```
+By default, any rule name is valid because of custom rules. To allow only
+built-in rules, use the
+[`markdownlint-config-schema-strict.json`][markdownlint-config-schema-strict]
+JSON Schema instead.
 
 [json-schema]: https://json-schema.org
 [markdownlint-config-schema]: markdownlint-config-schema.json
+[markdownlint-config-schema-strict]: markdownlint-config-schema-strict.json

schema/build-config-schema.js

@@ -9,7 +9,10 @@ const rules = require("../lib/rules");
 const jsonSchemaToTypeScript = require("json-schema-to-typescript");
 const { version } = require("../lib/constants");
 
-const schemaUri = `https://raw.githubusercontent.com/DavidAnson/markdownlint/v${version}/schema/markdownlint-config-schema.json`;
+const schemaName = "markdownlint-config-schema.json";
+const schemaUri = `https://raw.githubusercontent.com/DavidAnson/markdownlint/v${version}/schema/${schemaName}`;
+const schemaStrictName = "markdownlint-config-schema-strict.json";
+const schemaStrictUri = `https://raw.githubusercontent.com/DavidAnson/markdownlint/v${version}/schema/${schemaStrictName}`;
 
 // Schema scaffolding
 const schema = {
@@ -574,20 +577,24 @@ for (const [ tag, tagTags ] of Object.entries(tags)) {
 }
 
 // Write schema
-const schemaFile = path.join(__dirname, "markdownlint-config-schema.json");
+const schemaFile = path.join(__dirname, schemaName);
 fs.writeFileSync(schemaFile, JSON.stringify(schema, null, "  "));
 
-// Write TypeScript declaration
-// See https://github.com/bcherny/json-schema-to-typescript/issues/356 for why
-// additionalProperties is deleted
-const schemaDeclaration =
-  path.join(__dirname, "..", "lib", "configuration.d.ts");
-// @ts-ignore
-delete schema.additionalProperties;
-schema.title = "Configuration";
+// Create and write strict schema
+const schemaStrict = {
+  ...schema,
+  "$id": schemaStrictUri,
+  "additionalProperties": false
+};
+const schemaFileStrict = path.join(__dirname, schemaStrictName);
+fs.writeFileSync(schemaFileStrict, JSON.stringify(schemaStrict, null, "  "));
+
+// Write TypeScript declaration file
+const declarationStrictName = path.join(__dirname, "..", "lib", "configuration-strict.d.ts");
+schemaStrict.title = "ConfigurationStrict";
 jsonSchemaToTypeScript.compile(
   // @ts-ignore
-  schema,
+  schemaStrict,
   "UNUSED"
   // eslint-disable-next-line unicorn/prefer-top-level-await
-).then((declaration) => fs.writeFileSync(schemaDeclaration, declaration));
+).then((declaration) => fs.writeFileSync(declarationStrictName, declaration));

test/markdownlint-test.js

@@ -18,13 +18,9 @@ const constants = require("../lib/constants");
 const rules = require("../lib/rules");
 const customRules = require("./rules/rules.js");
 const configSchema = require("../schema/markdownlint-config-schema.json");
+const configSchemaStrict = require("../schema/markdownlint-config-schema-strict.json");
 
 const deprecatedRuleNames = new Set(constants.deprecatedRuleNames);
-const configSchemaStrict = {
-  ...configSchema,
-  "$id": `${configSchema.$id}-strict`,
-  "additionalProperties": false
-};
 const ajvOptions = {
   "allowUnionTypes": true
 };