Update: Support prettierignore and custom processors (#111)

* Ignore files in .prettierignore

Fixes #88

* Force the babylon parser when parsing not-js files

Forcing the parser stops errors that are caused by trying to run a JS
fragment through the graphql / markdown parsers.

The 'html' parser has not yet been released yet, but will be in Prettier
1.15.

This uses a block list over an allow list because I expect the list of
"file types with a prettier parser that could contain javascript fragments"
will grow at a slower pace than "file types with a prettier parser that
are variations of the javascript language".

Fixes #98, Fixes #81

.prettierignore

@@ -0,0 +1,5 @@
+package.json
+
+# this file doesn't exist, but we use it as a filename that should be ignored
+# by prettier in the tests
+ignore-me.js

eslint-plugin-prettier.js

@@ -356,6 +356,7 @@ module.exports = {
         const usePrettierrc =
           !context.options[1] || context.options[1].usePrettierrc !== false;
         const sourceCode = context.getSourceCode();
+        const filepath = context.getFilename();
         const source = sourceCode.text;
 
         // The pragma is only valid if it is found in a block comment at the very
@@ -397,19 +398,64 @@ module.exports = {
               context.options[0] === 'fb'
                 ? FB_PRETTIER_OPTIONS
                 : context.options[0];
+
             const prettierRcOptions =
               usePrettierrc &&
               prettier.resolveConfig &&
               prettier.resolveConfig.sync
-                ? prettier.resolveConfig.sync(context.getFilename(), {
+                ? prettier.resolveConfig.sync(filepath, {
                     editorconfig: true
                   })
                 : null;
+
+            // prettier.getFileInfo was added in v1.13
+            const prettierFileInfo =
+              prettier.getFileInfo && prettier.getFileInfo.sync
+                ? prettier.getFileInfo.sync(filepath, {
+                    ignorePath: '.prettierignore'
+                  })
+                : { ignored: false, inferredParser: null };
+
+            // Skip if file is ignored using a .prettierignore file
+            if (prettierFileInfo.ignored) {
+              return;
+            }
+
+            const initialOptions = {};
+
+            // ESLint suppports processors that let you extract and lint JS
+            // fragments within a non-JS language. In the cases where prettier
+            // supports the same language as a processor, we want to process
+            // the provided source code as javascript (as ESLint provides the
+            // rules with fragments of JS) instead of guessing the parser
+            // based off the filename. Otherwise, for instance, on a .md file we
+            // end up trying to run prettier over a fragment of JS using the
+            // markdown parser, which throws an error.
+            // If we can't infer the parser from from the filename, either
+            // because no filename was provided or because there is no parser
+            // found for the filename, use javascript.
+            // This is added to the options first, so that
+            // prettierRcOptions and eslintPrettierOptions can still override
+            // the parser.
+            //
+            // `parserBlocklist` should contain the list of prettier parser
+            // names for file types where:
+            // * Prettier supports parsing the file type
+            // * There is an ESLint processor that extracts JavaScript snippets
+            //   from the file type.
+            const parserBlocklist = [null, 'graphql', 'markdown', 'html'];
+            if (
+              parserBlocklist.indexOf(prettierFileInfo.inferredParser) !== -1
+            ) {
+              initialOptions.parser = 'babylon';
+            }
+
             const prettierOptions = Object.assign(
               {},
+              initialOptions,
               prettierRcOptions,
               eslintPrettierOptions,
-              { filepath: context.getFilename() }
+              { filepath }
             );
 
             const prettierSource = prettier.format(source, prettierOptions);

package.json

@@ -43,7 +43,7 @@
     "eslint-plugin-self": "^1.0.1",
     "mocha": "^3.1.2",
     "moment": "^2.18.1",
-    "prettier": "^1.10.2",
+    "prettier": "^1.13.0",
     "semver": "^5.3.0",
     "vue-eslint-parser": "^2.0.2"
   },

test/prettier.js

@@ -65,6 +65,24 @@ ruleTester.run('prettier', rule, {
       code: `var foo = {bar: 0};\n`,
       filename: getPrettierRcJsFilename('bracket-spacing'),
       options: [{ bracketSpacing: false }, { usePrettierrc: false }]
+    },
+    // Ignores filenames in .prettierignore
+    {
+      code: `("");\n`,
+      filename: getPrettierRcJsFilename('single-quote', 'ignore-me.js')
+    },
+    // Sets a default parser when it can't be inferred from the file extensions
+    {
+      code: `('');\n`,
+      filename: getPrettierRcJsFilename('single-quote', 'dummy.qqq')
+    },
+    // Overwrites the parser for file extensions prettier would try to format
+    // with not the babylon parser
+    // In the real world, eslint-plugin-markdown would transform file contents
+    // into JS snippets that would get passed to ESLint
+    {
+      code: `('');\n`,
+      filename: getPrettierRcJsFilename('single-quote', 'dummy.md')
     }
   ],
   invalid: [
@@ -175,9 +193,12 @@ function loadInvalidFixture(name) {
 
 /**
  * Builds a dummy javascript file path to trick prettier into resolving a specific .prettierrc file.
- * @param {string} name - Prettierrc fixture basename.
+ * @param {string} dir - Prettierrc fixture basename.
  * @returns {string} A javascript filename relative to the .prettierrc config.
  */
-function getPrettierRcJsFilename(name) {
-  return path.resolve(__dirname, `./prettierrc/${name}/dummy.js`);
+function getPrettierRcJsFilename(dir, file) {
+  // Use default parameters when we drop support for node 4
+  file = typeof file !== 'undefined' ? file : 'dummy.js';
+
+  return path.resolve(__dirname, `./prettierrc/${dir}/${file}`);
 }

yarn.lock

@@ -801,9 +801,9 @@ prelude-ls@~1.1.2:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/prelude-ls/-/prelude-ls-1.1.2.tgz#21932a549f5e52ffd9a827f570e04be62a97da54"
 
-prettier@^1.10.2:
-  version "1.10.2"
-  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.10.2.tgz#1af8356d1842276a99a5b5529c82dd9e9ad3cc93"
+prettier@^1.13.0:
+  version "1.14.3"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.14.3.tgz#90238dd4c0684b7edce5f83b0fb7328e48bd0895"
 
 process-nextick-args@~1.0.6:
   version "1.0.7"