From b5b306248ddd2a66e02260666a29d6338637093e Mon Sep 17 00:00:00 2001
From: kovenliao <kovenliao@yahoo-inc.com>
Date: Tue, 30 May 2017 13:11:12 +0800
Subject: [PATCH] fix sha generation, always create new instance

---
 spec/WebpackSHASpec.js  | 41 +++++++++++++++++++++++++++++++++++++++++
 src/webpack_sha_hash.js |  9 ++++++---
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/spec/WebpackSHASpec.js b/spec/WebpackSHASpec.js
index 43e58e6..4e129e7 100644
--- a/spec/WebpackSHASpec.js
+++ b/spec/WebpackSHASpec.js
@@ -120,4 +120,45 @@ describe("WebpackSHAHash", () => {
             });
         });
     });
+
+    it("Should generate same hash if content not changed", (done) => {
+        var config = {
+            entry: {
+                entry: path.join(FIXTURES, "entry.js")
+            },
+            plugins: [
+                new WebpackSHAHash()
+            ],
+            output: {
+                path: OUTPUT_DIR,
+                filename: "[name]-bundle.js",
+                chunkFilename: "[chunkhash].[id].chunk.js"
+            }
+        };
+
+        webpack(config, (err, stats) => {
+            expect(err).toBeFalsy();
+            expect(stats.compilation.errors).toEqual([]);
+            expect(stats.compilation.warnings).toEqual([]);
+
+            let firstRunResult = fs.readdirSync(OUTPUT_DIR);
+
+            expect(firstRunResult.length).toEqual(2);
+
+            rimraf(OUTPUT_DIR, () => {
+                webpack(config, (err, stats) => {
+                    expect(err).toBeFalsy();
+                    expect(stats.compilation.errors).toEqual([]);
+                    expect(stats.compilation.warnings).toEqual([]);
+
+                    let secondRunResult = fs.readdirSync(OUTPUT_DIR);
+
+                    expect(secondRunResult.length).toEqual(2);
+
+                    expect(firstRunResult).toEqual(secondRunResult);
+                    done();
+                });
+            });
+        });
+    });
 });
diff --git a/src/webpack_sha_hash.js b/src/webpack_sha_hash.js
index 24fc874..ff4e4fc 100644
--- a/src/webpack_sha_hash.js
+++ b/src/webpack_sha_hash.js
@@ -16,7 +16,7 @@ class WebpackSHAHash {
         this.hashingAlgorithm = options.hashingAlgorithm;
 
         try{
-            this.hashingAlgorithmInstance = createHash(this.hashingAlgorithm);
+            createHash(this.hashingAlgorithm);
         } catch(e) {
             throw new Error("You have most probably provided an invalid value for the 'hashingAlgorithm' option of the WebpackSHAHash plugin! Error details: " + e.stack + "\n -----------");
         }
@@ -54,6 +54,10 @@ class WebpackSHAHash {
         return result + moduleSource;
     }
 
+    generateHash(content) {
+        return createHash(this.hashingAlgorithm).update(content, "utf8").digest("hex");
+    }
+
     /**
      * Called by Webpack which gives a referencer to its compiler object.
      * Reference: https://github.com/webpack/docs/wiki/plugins
@@ -63,8 +67,7 @@ class WebpackSHAHash {
         compiler.plugin("compilation", (compilation) => {
             compilation.plugin("chunk-hash", (chunk, chunkHash) => {
                 const source = chunk.modules.sort(this.compareModules).map(this.getModuleSource).reduce(this.concatenateSource, ""); // we provide an initialValue in case there is an empty module source. Ref: http://es5.github.io/#x15.4.4.21
-                const hash = this.hashingAlgorithmInstance.update(source, "utf8");
-                const calculatedChunkHash = hash.digest("hex");
+                const calculatedChunkHash = this.generateHash(source);
 
                 chunkHash.digest = () => {
                     return calculatedChunkHash;