Adding optional argument to append fingerprint hash with a new name

Author: gcscoder

README.md

@@ -108,5 +108,24 @@ And in your layout:
 
 That's it! Now if you use a cleaner as suggested, along with file watching, you'll be able to run this in `development` and have `bundle.js` rebuild without fingerprinting, and your Rails app with use that directly. Once you build for production, your Rails app and your `bundle.js` will use a fingerprinted version of the file.
 
+### Managing multiple webpack builds
+
+If your build setup launches webpack multiple times a new hash will be generated with each run.  This can cause problems when using the default
+arguments.  The last run will overwrite any previously written hash value.  An additional parameter can be passed to tell the plugin to append a new named value that has the key from the subsequent run.
+
+Passing a name in the third paramenter will generate a new line in `asset_fingerprint.rb` having the name assigned to the new hash. For example:
+
+```
+AssetFingerprintPlugin(rubyConfigInitPath, true, 'CUSTOM_ASSET_FINGERPRINT')
+```
+
+will generate a new line in the file like this:
+
+```
+ASSET_FINGERPRINT = '0556f9ab7cbd607d10ed'
+CUSTOM_ASSET_FINGERPRINT = '921dcffe35e5f2740ef5'
+```
+
+
 ### Credit
 Concept adapted from @samullen - http://samuelmullen.com/articles/replacing-the-rails-asset-pipeline-with-webpack-and-yarn/

index.js

@@ -1,10 +1,11 @@
 const fs = require('fs');
 
-function AssetFingerprint(initializerDirectory, needsFingerprint = true) {
+function AssetFingerprint(initializerDirectory, needsFingerprint = true, fingerprintName) {
   _validateInitializerDirectory();
 
   this.initializerDirectory = initializerDirectory;
   this.needsFingerprint = needsFingerprint;
+  this.fingerprintName = fingerprintName || 'ASSET_FINGERPRINT';
 
   function _validateInitializerDirectory() {
     if (initializerDirectory === undefined) {
@@ -16,10 +17,13 @@ function AssetFingerprint(initializerDirectory, needsFingerprint = true) {
 AssetFingerprint.prototype.apply = function(compiler) {
   compiler.plugin('done', function(stats) {
     if (this.needsFingerprint) {
-      let output = `ASSET_FINGERPRINT = '${stats.hash}'`;
-      let initializerPath = `${this.initializerDirectory}/asset_fingerprint.rb`;
-
-      fs.writeFileSync(initializerPath, output);
+        let defaultRun = this.fingerprintName === 'ASSET_FINGERPRINT';
+        let initializerPath = `${this.initializerDirectory}/asset_fingerprint.rb`;
+        const newline = defaultRun ? '' : '\r\n';
+        const fsMethod = defaultRun ? 'writeFileSync' : 'appendFileSync';
+        let output = `${newline}${this.fingerprintName} = '${stats.hash}'`;
+        fs[fsMethod](initializerPath, output);
+        console.log(`asset-fingerprint-webpack-rails: updated file ${initializerPath} with ${this.fingerprintName} = ${stats.hash}`)
     }
   }.bind(this));
 }

spec/indexSpec.js

@@ -1,5 +1,6 @@
 describe("AssetFingerprint", function() {
   var AssetFingerprint = require('../index');
+  var fs = require('fs');
   var fingerprint;
 
   describe("initialization", function() {
@@ -37,5 +38,55 @@ describe("AssetFingerprint", function() {
         expect(fingerprint).toThrowError('Please supply a directory path for your initializer, such as `config/initializers`.');
       });
     });
+
+    describe("fingerprint name", function() {
+      it("should use ASSET_FINGERPRINT when no args are passed", function () {
+        var dir = 'config/initializers';
+        fingerprint = new AssetFingerprint(dir);
+        expect(fingerprint.fingerprintName).toEqual("ASSET_FINGERPRINT");
+      });
+
+      it("should use value when provided", function () {
+        var dir = 'config/initializers';
+        fingerprint = new AssetFingerprint(dir, true, "FINGERPRINT_VALUE");
+        expect(fingerprint.fingerprintName).toEqual("FINGERPRINT_VALUE");
+      });
+    });
+
+    describe("apply", function() {
+      beforeEach(function() {
+        spyOn(fs, "writeFileSync");
+        spyOn(fs, "appendFileSync");
+        spyOn(console, "log");
+      });
+
+      it("should call writeFileSync on default arguments", function() {
+        var dir = 'config/initializers';
+        fingerprint = new AssetFingerprint(dir);
+        fingerprint.apply({
+          plugin: function(status, callback) { callback({hash: "A1B2C3D4"}) }
+        });
+
+        expect(fs.writeFileSync).toHaveBeenCalledWith(
+          'config/initializers/asset_fingerprint.rb', "ASSET_FINGERPRINT = 'A1B2C3D4'");
+
+        expect(console.log).toHaveBeenCalledWith(
+          "asset-fingerprint-webpack-rails: updated file config/initializers/asset_fingerprint.rb with ASSET_FINGERPRINT = A1B2C3D4");
+      });
+
+      it("should call appendFileSync on provided fingerprint name argument", function() {
+        var dir = 'config/initializers';
+        fingerprint = new AssetFingerprint(dir, true, "FINGERPRINT_VALUE");
+        fingerprint.apply({
+          plugin: function(status, callback) { callback({hash: "Z1Y2X3W4"}) }
+        });
+
+        expect(fs.appendFileSync).toHaveBeenCalledWith(
+          'config/initializers/asset_fingerprint.rb', "\r\nFINGERPRINT_VALUE = 'Z1Y2X3W4'");
+
+        expect(console.log).toHaveBeenCalledWith(
+          "asset-fingerprint-webpack-rails: updated file config/initializers/asset_fingerprint.rb with FINGERPRINT_VALUE = Z1Y2X3W4");
+      });
+    });
   });
 });