Introduce type declaration file for project after updating typescript dependency to 3.7.2.

example/typescript/.gitignore

@@ -0,0 +1 @@
+type-check.js

example/typescript/tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
+    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
+    "strict": true,                           /* Enable all strict type-checking options. */
+    "noUnusedLocals": true,                   /* Report errors on unused locals. */
+    "noUnusedParameters": true,               /* Report errors on unused parameters. */
+    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    "forceConsistentCasingInFileNames": true  /* Disallow inconsistently-cased references to the same file. */
+  }
+}

example/typescript/type-check.ts

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+// Attempt to validate all the type declarations in markdownlint.d.ts
+
+import markdownlint from "../..";
+
+const assert = require("assert");
+const { URL } = require("url");
+const markdownlintJsonPath = "../../.markdownlint.json";
+
+function assertConfiguration(config: markdownlint.Configuration) {
+  assert(!!config);
+  assert.equal(config["line-length"], false);
+  assert.deepEqual(config["no-inline-html"], {
+    "allowed_elements": [
+      "a"
+    ]
+  });
+  // config assignment is covered by markdownlint.Options
+}
+
+function assertConfigurationCallback(err: Error | null, config?: markdownlint.Configuration) {
+  assert(!err);
+  config && assertConfiguration(config);
+}
+
+function assertLintResults(results: markdownlint.LintResults) {
+  assert(!!results);
+  assert.equal(results["string"].length, 1);
+  assert.equal(results["string"][0].lineNumber, 1);
+  assert.deepEqual(results["string"][0].ruleNames, [ "MD047", "single-trailing-newline" ]);
+  assert.equal(results["string"][0].ruleDescription, "Files should end with a single newline character");
+  assert.equal(results["string"][0].ruleInformation.replace(/v\d+\.\d+\.\d+/, "v0.0.0"), "https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md047");
+  assert.equal(results["string"][0].errorDetail, null);
+  assert.equal(results["string"][0].errorContext, null);
+  assert.deepEqual(results["string"][0].errorRange, [ 9, 1 ]);
+  assert(!!results["string"][0].fixInfo);
+  assert.equal(results["string"][0].fixInfo.editColumn, 10);
+  assert(!results["string"][0].fixInfo.deleteCount);
+  assert.equal(results["string"][0].fixInfo.insertText, "\n");
+  assert.equal(results["../bad.md"].length, 2);
+  results = {
+    "key": [
+      {
+        "lineNumber": 1,
+        "ruleNames": [ "rule", "names" ],
+        "ruleDescription": "description",
+        "ruleInformation": "https://example.com/ruleInformation",
+        "errorDetail": "detail",
+        "errorContext": "context",
+        "errorRange": [ 1, 2 ],
+        "fixInfo": {
+          "editColumn": 1,
+          "deleteCount": 1,
+          "insertText": "text"
+        }
+      }
+    ]
+  };
+}
+
+function assertLintResultsCallback(err: Error | null, results?: markdownlint.LintResults) {
+  assert(!err);
+  results && assertLintResults(results);
+}
+
+assertConfiguration(markdownlint.readConfigSync(markdownlintJsonPath));
+assertConfiguration(markdownlint.readConfigSync(markdownlintJsonPath, [ JSON.parse ]));
+
+// The following call is valid, but disallowed because TypeScript does not
+// currently propagate {ConfigurationParser[] | null} into the .d.ts file.
+// markdownlint.readConfig(markdownlintJsonPath, null, assertConfigCallback);
+markdownlint.readConfig(markdownlintJsonPath, [ JSON.parse ], assertConfigurationCallback);
+
+let options: markdownlint.Options;
+options = {
+  "files": [ "../bad.md" ],
+  "strings": {
+    "string": "# Heading"
+  },
+  "config": {
+    "no-missing-space-atx": false,
+    "no-hard-tabs": {
+      "code_blocks": true
+    }
+  },
+  "customRules": undefined,
+  "frontMatter": /---/,
+  "handleRuleFailures": false,
+  "noInlineConfig": false,
+  "resultVersion": 3,
+  "markdownItPlugins": [ [ require("markdown-it-sub") ] ]
+};
+
+assertLintResults(markdownlint.sync(options));
+markdownlint(options, assertLintResultsCallback);
+
+options.files = "../bad.md";
+assertLintResults(markdownlint.sync(options));
+markdownlint(options, assertLintResultsCallback);
+
+const testRule = {
+  "names": [ "test-rule" ],
+  "description": "Test rule",
+  "information": new URL("https://example.com/test-rule"),
+  "tags": [ "test-tag" ],
+  "function": function rule(params: markdownlint.RuleParams, onError: markdownlint.RuleOnError) {
+    assert(!!params);
+    assert(!!onError);
+    let ruleParams: markdownlint.RuleParams;
+    ruleParams = {
+      "name": "name",
+      "tokens": <markdownlint.MarkdownItToken[]>[],
+      "lines": [
+        "one",
+        "two"
+      ],
+      "frontMatterLines": [
+        "three"
+      ],
+      "config": options.config
+    };
+    assert(ruleParams);
+    let ruleOnErrorInfo: markdownlint.RuleOnErrorInfo;
+    ruleOnErrorInfo = {
+      "lineNumber": 1,
+      "details": "details",
+      "context": "context",
+      "range": [ 1, 2 ],
+      "fixInfo": {
+        "lineNumber": 1,
+        "editColumn": 1,
+        "deleteCount": 1,
+        "insertText": "text"
+      }
+    };
+    assert(ruleOnErrorInfo);
+    false && onError(ruleOnErrorInfo);
+  }
+};
+
+options.customRules = [ testRule ];
+assertLintResults(markdownlint.sync(options));
+markdownlint(options, assertLintResultsCallback);