Add option to resolve elm-format binary from local project directory

src/helpers.js

@@ -1,5 +1,7 @@
 'use babel';
 
+import fs from 'fs';
+import path from 'path';
 import open from 'opn';
 
 export const installInstructions = {
@@ -11,3 +13,27 @@ export const installInstructions = {
     text: 'Open instructions',
   }],
 };
+
+const findElmFormatBinary = (dir) => {
+  const elmFormatFile = path.join(dir, 'node_modules', '.bin', 'elm-format');
+
+  try {
+    fs.accessSync(elmFormatFile, fs.constants.F_OK);
+    return elmFormatFile;
+  } catch (e) {
+    return false;
+  }
+};
+
+export const resolveLocalBinary = () => {
+  const projectPaths = atom.project.getPaths();
+  const results = projectPaths
+    .map(findElmFormatBinary)
+    .filter(a => a !== false);
+
+  if (results && results[0]) {
+    return results[0];
+  }
+
+  return false;
+};

src/index.js

@@ -5,7 +5,7 @@ import path from 'path';
 import childProcess from 'child_process';
 import fs from 'fs';
 import config from './settings';
-import { installInstructions } from './helpers';
+import { installInstructions, resolveLocalBinary } from './helpers';
 
 export default {
   config,
@@ -82,12 +82,27 @@ export default {
     try {
       // Reset the error tracker.
       this.errorLineNum = null;
-      const binary = atom.config.get('elm-format.binary');
-      const elmVersion = atom.config.get('elm-format.elmVersion') || '0.19';
+      let binary = atom.config.get('elm-format.binary');
+      let elmVersion = atom.config.get('elm-format.elmVersion') || '0.19';
+
+      if (atom.config.get('elm-format.preferLocalBinary')) {
+        const localBinary = resolveLocalBinary();
+
+        if (localBinary) {
+          binary = localBinary;
+          elmVersion = false;
+        }
+      }
+
+      const args = ['--stdin'];
+
+      if (elmVersion) {
+        args.push('--elm-version', elmVersion);
+      }
 
       const { status, stdout, stderr } = childProcess.spawnSync(
         binary,
-        ['--elm-version', elmVersion, '--stdin'], { input: editor.getText() });
+        args, { input: editor.getText() });
 
       switch (status) {
         case 0: {

src/settings.js

@@ -6,6 +6,13 @@ export default {
     description: 'Path for elm-format',
     type: 'string',
     default: 'elm-format',
+    order: 7,
+  },
+  preferLocalBinary: {
+    title: 'Prefer local binary',
+    description: 'Try to resolve the binary from the current project\'s directories if possible',
+    type: 'boolean',
+    default: false,
     order: 6,
   },
   elmVersion: {