webpack: Help handlebars compilation not be terri-slow.

closes CNVS-27874

TEST PLAN:
 1) run webpack build
 2) should be fast

Change-Id: I3d0b07cb7417cbd235bd628375d9888c6cc8d090
Reviewed-on: https://gerrit.instructure.com/74112
QA-Review: August Thornton <august@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
Product-Review: Jon Jensen <jon@instructure.com>
Tested-by: Jenkins

frontend_build/brandableCss.js

@@ -0,0 +1,41 @@
+// This is a port of some of the functionality in
+// lib/brandable_css.rb, because shelling out to run this
+// stuff take FOREVER.  That means for the time being, changes here
+// if they happen may need to be mirrored in that file.
+var fs = require('fs');
+var yaml = require('js-yaml');
+var child_process = require('child_process');
+var configDocument = yaml.safeLoad(fs.readFileSync(__dirname + '/../config/brandable_css.yml', 'utf8'));
+var variants = Object.keys(configDocument.variants);
+var manifestKeySeperator = configDocument.manifest_key_seperator;
+var useCompressed = process.env.RAILS_ENV == 'production'
+var SassStyle = process.env.SASS_STYLE || (useCompressed ? 'compressed' : 'nested');
+
+// load checksums data for fast retrieval during parsing
+var checksumsFilePath = "/../" + configDocument.paths.bundles_with_deps + SassStyle;
+var checksumsJson = JSON.parse(fs.readFileSync(__dirname + checksumsFilePath, 'utf8'))
+var combinedChecksums = {}
+Object.keys(checksumsJson).forEach(function(key){
+  if(checksumsJson.hasOwnProperty(key)){
+    var jsonObj = checksumsJson[key]
+    combinedChecksums[key] = {
+      combinedChecksum: jsonObj.combinedChecksum,
+      includesNoVariables: jsonObj.includesNoVariables
+    }
+  }
+})
+
+var cacheFor = function(bundleName, variant){
+  var key = [bundleName + ".scss", variant].join(manifestKeySeperator);
+  return combinedChecksums[key];
+}
+
+var fingerprint = function(bundleName){
+  var fingerprints = {}
+  variants.forEach(function(variant){
+    fingerprints[variant] = cacheFor(bundleName, variant);
+  })
+  return fingerprints;
+};
+
+module.exports.allFingerprintsFor = fingerprint;

frontend_build/i18nLinerHandlebars.js

@@ -9,7 +9,7 @@ var EmberHandlebars = require('ember-template-compiler').EmberHandlebars;
 var ScopedHbsExtractor = require(__dirname + '/../gems/canvas_i18nliner/js/scoped_hbs_extractor');
 var PreProcessor = require(__dirname + '/../gems/canvas_i18nliner/node_modules/i18nliner-handlebars/dist/lib/pre_processor')['default'];
 var fs = require('fs');
-var child_process = require('child_process');
+var brandableCss = require(__dirname + "/brandableCss")
 
 var compileHandlebars = function(data){
   var path = data.path;
@@ -35,6 +35,8 @@ var compileHandlebars = function(data){
   }
 };
 
+
+
 var emitTemplate = function(path, name, result, dependencies, cssRegistration, partialRegistration){
   var moduleName = "jst/" + path.replace(/.*\/\jst\//, '').replace(/\.handlebars/, "");
   return "" +
@@ -60,13 +62,7 @@ var buildCssReference = function(name){
     var cssStat = fs.statSync(matchingCssPath);
     if(cssStat.isFile()){
       var bundle = "jst/" + name;
-      var fingerprintArgs = ["exec", "rake", "brand_configs:fingerprints["+bundle+"]"];
+      var cached = brandableCss.allFingerprintsFor(bundle)
-      var fingerprintOutput = child_process.spawnSync("bundle", fingerprintArgs);
-      if(fingerprintOutput.error){
-        console.log("ERROR IN FINGERPRINTING", fingerprintOutput.error);
-        throw fingerprintOutput.error;
-      }
-      var cached = JSON.parse(fingerprintOutput.stdout.toString());
       var firstVariant = Object.keys(cached)[0];
       var options = "";
       if(cached[firstVariant]['includesNoVariables']){

lib/brandable_css.rb

@@ -2,6 +2,11 @@ require 'pathname'
 require 'yaml'
 require 'open3'
 
+# Some of the functionality for fingerprint lookup here is mirrored in
+# frontend_build/brandableCss.js, because shelling out to run this
+# stuff take FOREVER in the webpack build.  That means for the time being,
+# changes here if they happen may need to be mirrored in that file.
+
 module BrandableCSS
   APP_ROOT = defined?(Rails) && Rails.root || Pathname.pwd
   CONFIG = YAML.load_file(APP_ROOT.join('config/brandable_css.yml')).freeze