New: add support for meta info in code blocks

Fixes: eslint#170

README.md

@@ -57,7 +57,7 @@ module.exports = {
         {
             // 3. Optionally, customize the configuration ESLint uses for ```js
             // fenced code blocks inside .md files.
-            files: ["**/*.md/*.js"],
+            files: ["**/*.md/*.js", "**/*.md/*.js:*"],
             // ...
             rules: {
                 // ...
@@ -87,12 +87,17 @@ module.exports = {
         // ...
         {
             // 1. Target ```js code blocks in .md files.
-            files: ["**/*.md/*.js"],
+            files: ["**/*.md/*.js", "**/*.md/*.js:*"],
             rules: {
                 // 2. Disable other rules.
                 "no-console": "off",
                 "import/no-unresolved": "off"
             }
+        },
+        {
+            // 2. Target "```js esm" code blocks
+            files: ["**/*.md/*.js:esm"],
+            parserOptions: { type: "module" }
         }
     ]
 };
@@ -167,7 +172,7 @@ module.exports = {
             // In v2, configuration for fenced code blocks is separate from the
             // containing Markdown file. Each code block has a virtual filename
             // appended to the Markdown file's path.
-            files: ["**/*.md/*.js"],
+            files: ["**/*.md/*.js", "**/*.md/*.js:*"],
             // Configuration for fenced code blocks goes with the override for
             // the code block's virtual filename, for example:
             parserOptions: {
@@ -195,7 +200,10 @@ module.exports = {
             processor: "markdown/markdown"
         },
         {
-            files: ["**/*.{md,mkdn,mdown,markdown}/*.{js,javascript,jsx,node}"]
+            files: [
+                "**/*.{md,mkdn,mdown,markdown}/*.{js,javascript,jsx,node}",
+                "**/*.{md,mkdn,mdown,markdown}/*.{js,javascript,jsx,node}:*"
+            ]
             // ...
         }
     ]

lib/processor.js

@@ -252,7 +252,7 @@ function preprocess(text) {
     });
 
     return blocks.map((block, index) => ({
-        filename: `${index}.${block.lang}`,
+        filename: `${index}.${block.lang}${block.meta ? `:${block.meta}` : ""}`,
         text: [
             ...block.comments,
             block.value,

tests/lib/processor.js

@@ -273,16 +273,16 @@ describe("processor", () => {
             assert.strictEqual(blocks[0].filename, "0.JavaScript");
         });
 
-        it("should ignore anything after the first word of the info string", () => {
+        it("should should handle meta info", () => {
             const code = [
-                "```js more words are ignored",
-                "var answer = 6 * 7;",
+                "```js esm",
+                "export {};",
                 "```"
             ].join("\n");
             const blocks = processor.preprocess(code);
 
             assert.strictEqual(blocks.length, 1);
-            assert.strictEqual(blocks[0].filename, "0.js");
+            assert.strictEqual(blocks[0].filename, "0.js:esm");
         });
 
         it("should ignore leading whitespace in the info string", () => {
@@ -294,7 +294,7 @@ describe("processor", () => {
             const blocks = processor.preprocess(code);
 
             assert.strictEqual(blocks.length, 1);
-            assert.strictEqual(blocks[0].filename, "0.js");
+            assert.strictEqual(blocks[0].filename, "0.js:ignores leading whitespace");
         });
 
         it("should ignore trailing whitespace in the info string", () => {