From 5178e8d2c65e7e0caf2f45094aec667ef706ad31 Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@github.com>
Date: Fri, 29 Jul 2016 16:55:27 -0600
Subject: [PATCH] Pre-build less cache in build.js before packaging

---
 build/build.js                   |  2 +
 build/config.js                  |  3 +-
 build/lib/prebuild-less-cache.js | 78 ++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+), 1 deletion(-)
 create mode 100644 build/lib/prebuild-less-cache.js

diff --git a/build/build.js b/build/build.js
index 781d9b061..26e49cd76 100755
--- a/build/build.js
+++ b/build/build.js
@@ -11,6 +11,7 @@ const transpileCoffeeScriptPaths = require('./lib/transpile-coffee-script-paths'
 const transpileCsonPaths = require('./lib/transpile-cson-paths')
 const transpilePegJsPaths = require('./lib/transpile-peg-js-paths')
 const generateModuleCache = require('./lib/generate-module-cache')
+const prebuildLessCache = require('./lib/prebuild-less-cache')
 const generateMetadata = require('./lib/generate-metadata')
 const packageApplication = require('./lib/package-application')
 
@@ -21,5 +22,6 @@ transpileCoffeeScriptPaths()
 transpileCsonPaths()
 transpilePegJsPaths()
 generateModuleCache()
+prebuildLessCache()
 generateMetadata()
 packageApplication()
diff --git a/build/config.js b/build/config.js
index b45ca106f..b92a74e26 100644
--- a/build/config.js
+++ b/build/config.js
@@ -12,11 +12,12 @@ const repositoryRootPath = path.resolve(__dirname, '..')
 const buildOutputPath = path.join(repositoryRootPath, 'out')
 const intermediateAppPath = path.join(buildOutputPath, 'app')
 const cachePath = path.join(repositoryRootPath, 'cache')
+const homeDirPath = process.env.HOME || process.env.USERPROFILE
 
 module.exports = {
   appMetadata, channel,
   repositoryRootPath, buildOutputPath, intermediateAppPath,
-  cachePath
+  cachePath, homeDirPath
 }
 
 function getChannel () {
diff --git a/build/lib/prebuild-less-cache.js b/build/lib/prebuild-less-cache.js
new file mode 100644
index 000000000..a1119bd6d
--- /dev/null
+++ b/build/lib/prebuild-less-cache.js
@@ -0,0 +1,78 @@
+'use strict'
+
+const fs = require('fs')
+const glob = require('glob')
+const path = require('path')
+const LessCache = require('less-cache')
+
+const CONFIG = require('../config')
+const LESS_CACHE_VERSION =require('less-cache/package.json').version
+const FALLBACK_VARIABLE_IMPORTS = '@import "variables/ui-variables";\n@import "variables/syntax-variables";\n'
+
+module.exports = function () {
+  const cacheDirPath = path.join(CONFIG.intermediateAppPath, 'less-compile-cache')
+  console.log(`Generating pre-built less cache in ${cacheDirPath}`)
+
+  // Group bundled packages into UI themes, syntax themes, and non-theme packages
+  const uiThemes = []
+  const syntaxThemes = []
+  const nonThemePackages = []
+  for (let packageName in CONFIG.appMetadata.packageDependencies) {
+    const packageMetadata = require(path.join(CONFIG.intermediateAppPath, 'node_modules', packageName, 'package.json'))
+    if (packageMetadata.theme === 'ui') {
+      uiThemes.push(packageName)
+    } else if (packageMetadata.theme === 'syntax') {
+      syntaxThemes.push(packageName)
+    } else {
+      nonThemePackages.push(packageName)
+    }
+  }
+
+  // Warm cache for every combination of the default UI and syntax themes,
+  // because themes assign variables which may be used in any style sheet.
+  for (let uiTheme of uiThemes) {
+    for (let syntaxTheme of syntaxThemes) {
+      // Build a LessCache instance with import paths based on the current theme combination
+      const lessCache = new LessCache({
+        cacheDir: cacheDirPath,
+        fallbackDir: path.join(CONFIG.homeDirPath, '.atom', 'compile-cache', 'prebuild-less', LESS_CACHE_VERSION),
+        syncCaches: true,
+        resourcePath: CONFIG.intermediateAppPath,
+        importPaths: [
+          path.join(CONFIG.intermediateAppPath, 'node_modules', syntaxTheme, 'styles'),
+          path.join(CONFIG.intermediateAppPath, 'node_modules', uiTheme, 'styles'),
+          path.join(CONFIG.intermediateAppPath, 'static', 'variables'),
+          path.join(CONFIG.intermediateAppPath, 'static'),
+        ]
+      })
+
+      function cacheCompiledCSS(lessFilePath, importFallbackVariables) {
+        let lessSource = fs.readFileSync(lessFilePath, 'utf8')
+        if (importFallbackVariables) {
+          lessSource = FALLBACK_VARIABLE_IMPORTS + lessSource
+        }
+        lessCache.cssForFile(lessFilePath, lessSource)
+      }
+
+      // Cache all styles in static; don't append variable imports
+      for (let lessFilePath of glob.sync(path.join(CONFIG.intermediateAppPath, 'static', '**', '*.less'))) {
+        cacheCompiledCSS(lessFilePath, false)
+      }
+
+      // Cache styles for all bundled non-theme packages
+      for (let nonThemePackage of nonThemePackages) {
+        for (let lessFilePath of glob.sync(path.join(CONFIG.intermediateAppPath, 'node_modules', nonThemePackage, '**', '*.less'))) {
+          cacheCompiledCSS(lessFilePath, true)
+        }
+      }
+
+      // Cache styles for this UI theme
+      const uiThemeMainPath = path.join(CONFIG.intermediateAppPath, 'node_modules', uiTheme, 'index.less')
+      cacheCompiledCSS(uiThemeMainPath, true)
+
+      // Cache styles for this syntax theme
+      const syntaxThemeMainPath = path.join(CONFIG.intermediateAppPath, 'node_modules', syntaxTheme, 'index.less')
+      cacheCompiledCSS(syntaxThemeMainPath, true)
+    }
+  }
+}