Add script/redownload-electron-bins.js

This makes sure we download the correct version
of the electron-vendored "mksnapshot" binary.

This will also automatically download the version in sync with Atom,
if this module is being installed
as a dependency in the main Atom repository.

Author: DeeDeeG

package.json

@@ -15,7 +15,8 @@
     "report:coverage": "nyc report --reporter=cobertura --reporter=html --reporter=lcovonly",
     "lint": "eslint --max-warnings 0 test lib",
     "fetch-schema": "node script/fetch-schema",
-    "relay": "relay-compiler --src ./lib --schema graphql/schema.graphql"
+    "relay": "relay-compiler --src ./lib --schema graphql/schema.graphql",
+    "postinstall": "node script/redownload-electron-bins.js"
   },
   "engines": {
     "atom": ">=1.37.0"

script/redownload-electron-bins.js

@@ -0,0 +1,48 @@
+// Based on: https://github.com/atom/atom/blob/v1.51.0/script/redownload-electron-bins.js
+
+let downloadMksnapshotPath
+
+try {
+  downloadMksnapshotPath = require.resolve('electron-mksnapshot/download-mksnapshot.js');
+} catch { }
+
+if (typeof(downloadMksnapshotPath) !== 'undefined') {
+
+  const { spawn } = require('child_process');
+  const path = require('path');
+  const fs = require('fs');
+
+  const atomRepoPath = path.join('..', '..', '..', '..', 'atom', 'package.json');
+  const electronVersion = fs.existsSync(atomRepoPath) ? require(atomrepoPath).electronVersion : '6.1.12'
+  // TODO: Keep the above "electronVersion" in sync with "electronVersion" from Atom's package.json
+
+  if (process.env.ELECTRON_CUSTOM_VERSION !== electronVersion) {
+    const electronEnv = process.env.ELECTRON_CUSTOM_VERSION;
+    console.info(
+      `env var ELECTRON_CUSTOM_VERSION is not set,\n` +
+        `or doesn't match electronVersion in atom/package.json.\n` +
+        `(is: "${electronEnv}", wanted: "${electronVersion}").\n` +
+        `Setting, and re-downloading mksnapshot.\n`
+    );
+
+    process.env.ELECTRON_CUSTOM_VERSION = electronVersion;
+    const downloadMksnapshot = spawn('node', [downloadMksnapshotPath]);
+    var exitStatus;
+
+    downloadMksnapshot.on('close', code => {
+      if (code === 0) {
+        exitStatus = 'success';
+      } else {
+        exitStatus = 'error';
+      }
+
+      console.info(`info: Done re-downloading mksnapshot. Status: ${exitStatus}`);
+    });
+  } else {
+    console.info(
+      'info: env var "ELECTRON_CUSTOM_VERSION" is already set correctly.\n(No need to re-download mksnapshot). Skipping.\n'
+    );
+  }
+} else {
+  console.log('devDependency "electron-mksnapshot/download-mksnapshot.js" not found.\nSkipping "redownload electron bins" script.\n')
+}