Allow logging for Prism to be toggled (#75)

* Allow logging for Prism to be toggled

* Fix mocking in tests, avoid cross-contamination

* Make eslint happy

CHANGELOG.md

@@ -18,6 +18,7 @@ See `PUBLISH.md` for instructions on how to publish a new version.
 -->
 
 
+- (minor) Allow logging for Prism to be toggled
 - (patch) Manually track loaded Prism components
 
 # v1.8.0 - aaf8532

README.md

@@ -1162,6 +1162,7 @@ Pass options for this plugin as the `prismjs` property of the `do-markdownit` pl
 Set this property to `false` to disable this plugin.
 
 - `delimiter` (`string`, optional, defaults to `','`): String to split fence information on.
+- `logging` (`boolean`, optional, defaults to `false`): Whether to log errors to the console.
 </details>
 
 ### limit_tokens

modifiers/prismjs.js

@@ -30,6 +30,7 @@ const { languages, languageAliases, getDependencies } = require('../util/prism_u
 /**
  * @typedef {Object} PrismJsOptions
  * @property {string} [delimiter=','] String to split fence information on.
+ * @property {boolean} [logging=false] Whether to log errors to the console.
  */
 
 /**
@@ -43,16 +44,17 @@ const loaded = new Set();
  * Helper to load in a Prism component if not yet loaded.
  *
  * @param {string} component Prism component name to be loaded.
+ * @param {boolean} logging Whether to log errors to the console.
  * @private
  */
-const loadComponent = component => {
+const loadComponent = (component, logging) => {
     if (loaded.has(component)) return;
     try {
         // eslint-disable-next-line import/no-dynamic-require
         require(`../vendor/prismjs/components/prism-${component}`)(Prism);
         loaded.add(component);
     } catch (err) {
-        console.error('Failed to load Prism component', component, err);
+        if (logging) console.error('Failed to load Prism component', component, err);
     }
 };
 
@@ -171,8 +173,8 @@ module.exports = (md, options) => {
             const { before, inside, after } = extractCodeBlock(rendered, language);
 
             // Load requirements for language
-            getDependencies(language.clean).forEach(loadComponent);
-            loadComponent(language.clean);
+            getDependencies(language.clean).forEach(dep => loadComponent(dep, !!optsObj.logging));
+            loadComponent(language.clean, !!optsObj.logging);
 
             // If we failed to load the language (it's a dynamic require), return original
             if (!(language.clean in Prism.languages)) return rendered;
@@ -184,7 +186,7 @@ module.exports = (md, options) => {
             return `${before}${highlighted}${after}`;
         } catch (err) {
             // Fallback to no Prism if render fails
-            console.error('Bad Prism render occurred', err);
+            if (optsObj.logging) console.error('Bad Prism render occurred', err);
             return rendered;
         }
     };

modifiers/prismjs.test.js

@@ -16,7 +16,7 @@ limitations under the License.
 
 'use strict';
 
-const md = require('markdown-it')().use(require('./prismjs'));
+const md = require('markdown-it')().use(require('./prismjs'), { logging: true });
 
 it('handles a code fence with a language (adding the class to the pre + highlighting)', () => {
     expect(md.render('```nginx\nserver {\n    try_files test =404;\n}\n```')).toBe(`<pre class="language-nginx"><code class="language-nginx"><span class="token directive"><span class="token keyword">server</span></span> <span class="token punctuation">{</span>
@@ -33,11 +33,26 @@ it('handles a code fence with a language alias', () => {
 });
 
 it('does not repeatedly load a modifier component', () => {
-    const error = jest.spyOn(global.console, 'error');
-    md.render('```ts\nconsole.log("test");\n```\n\n```ts\nconsole.log("test");\n```');
-    expect(error).not.toHaveBeenCalledWith(expect.stringContaining('Failed to load Prism component'), 'js-templates', expect.anything());
-    error.mockReset();
-    error.mockRestore();
+    // Reset modules in case the modifier was already loaded
+    jest.resetModules();
+
+    // Mock the modifier to track how many times it is called
+    const callCount = jest.fn();
+    jest.doMock('../vendor/prismjs/components/prism-js-templates', () => {
+        const actual = jest.requireActual('../vendor/prismjs/components/prism-js-templates');
+        return (...args) => {
+            callCount();
+            return actual(...args);
+        };
+    });
+
+    // Process some Markdown that uses a language with the modifier twice
+    const mdTemp = require('markdown-it')().use(require('./prismjs'));
+    mdTemp.render('```ts\nconsole.log("test");\n```\n\n```ts\nconsole.log("test");\n```');
+    expect(callCount).toHaveBeenCalledTimes(1);
+
+    // Clean up the mock
+    jest.dontMock('../vendor/prismjs/components/prism-js-templates');
 });
 
 it('does not pollute global scope', () => {
@@ -51,6 +66,64 @@ it('does not pollute global scope', () => {
     expect(global.Prism).toBeUndefined();
 });
 
+describe('Error logging', () => {
+    it('does log errors when logging is enabled', () => {
+        // Reset modules in case the language was already loaded
+        jest.resetModules();
+
+        // Mock the language to track how many times it is called, and to throw an error
+        const callCount = jest.fn();
+        jest.doMock('../vendor/prismjs/components/prism-typescript', () => () => {
+            callCount();
+            throw new Error('test');
+        });
+
+        // Spy on console.error to check that it is called
+        const error = jest.spyOn(global.console, 'error');
+
+        // Process some Markdown that uses the language
+        const mdTemp = require('markdown-it')().use(require('./prismjs'), { logging: true });
+        mdTemp.render('```ts\nconsole.log("test");\n```');
+
+        // Check the mock was called and the error was logged
+        expect(callCount).toHaveBeenCalledTimes(1);
+        expect(error).toHaveBeenCalledWith('Failed to load Prism component', 'typescript', expect.any(Error));
+
+        // Clean up the mocks
+        error.mockReset();
+        error.mockRestore();
+        jest.dontMock('../vendor/prismjs/components/prism-typescript');
+    });
+
+    it('does not log errors when logging is disabled', () => {
+        // Reset modules in case the language was already loaded
+        jest.resetModules();
+
+        // Mock the component to track how many times it is called, and to throw an error
+        const callCount = jest.fn();
+        jest.doMock('../vendor/prismjs/components/prism-typescript', () => () => {
+            callCount();
+            throw new Error('test');
+        });
+
+        // Spy on console.error to check that it is called
+        const error = jest.spyOn(global.console, 'error');
+
+        // Process some Markdown that uses the language
+        const mdTemp = require('markdown-it')().use(require('./prismjs'));
+        mdTemp.render('```ts\nconsole.log("test");\n```');
+
+        // Check the mock was called and the error was logged
+        expect(callCount).toHaveBeenCalledTimes(1);
+        expect(error).not.toHaveBeenCalled();
+
+        // Clean up the mocks
+        error.mockReset();
+        error.mockRestore();
+        jest.dontMock('../vendor/prismjs/components/prism-typescript');
+    });
+});
+
 describe('HTML preservation', () => {
     // This does pollute the tests, no longer isolated, but is needed to inject HTML into the code blocks
     const mdHtml = require('markdown-it')()