Use the before emit hook to check if files exist (#36)

* Use the before emit hook to check if files exist

- Add an option to use this hook.
- When this plugin is used with other loaders such as ts-loader and
vue-loader, this option improves the overall build time. In our case,
the build time reduced by 5-10 seconds.

index.js

@@ -142,32 +142,63 @@ CaseSensitivePathsPlugin.prototype.apply = function (compiler) {
     this.reset();
   };
 
+  const checkFile = (pathName, data, done) => {
+    this.fileExistsWithCase(pathName, (realName) => {
+      if (realName) {
+        if (realName === '!nonexistent') {
+          // If file does not exist, let Webpack show a more appropriate error.
+          done(null, data);
+        } else {
+          done(new Error(`[CaseSensitivePathsPlugin] \`${pathName}\` does not match the corresponding path on disk ${realName}`));
+        }
+      } else {
+        done(null, data);
+      }
+    });
+  };
+
   const onAfterResolve = (data, done) => {
     this.primeCache(() => {
       // Trim ? off, since some loaders add that to the resource they're attemping to load
       let pathName = data.resource.split('?')[0];
       pathName = pathName.normalize ? pathName.normalize('NFC') : pathName;
 
-      this.fileExistsWithCase(pathName, (realName) => {
-        if (realName) {
-          if (realName === '!nonexistent') {
-            // If file does not exist, let Webpack show a more appropriate error.
-            done(null, data);
-          } else {
-            done(new Error(`[CaseSensitivePathsPlugin] \`${pathName}\` does not match the corresponding path on disk ${realName}`));
-          }
-        } else {
-          done(null, data);
-        }
-      });
+      checkFile(pathName, data, done);
     });
   };
 
   if (compiler.hooks) {
     compiler.hooks.done.tap('CaseSensitivePathsPlugin', onDone);
-    compiler.hooks.normalModuleFactory.tap('CaseSensitivePathsPlugin', (nmf) => {
-      nmf.hooks.afterResolve.tapAsync('CaseSensitivePathsPlugin', onAfterResolve);
-    });
+    if (this.options.useBeforeEmitHook) {
+      if (this.options.debug) {
+        console.log('[CaseSensitivePathsPlugin] Using the hook for before emit.');
+      }
+      compiler.hooks.emit.tapAsync('CaseSensitivePathsPlugin', (compilation, callback) => {
+        let resolvedFilesCount = 0;
+        const errors = [];
+        this.primeCache(() => {
+          compilation.fileDependencies.forEach((filename) => {
+            checkFile(filename, filename, (error) => {
+              resolvedFilesCount += 1;
+              if (error) {
+                errors.push(error);
+              }
+              if (resolvedFilesCount === compilation.fileDependencies.size) {
+                if (errors.length) {
+                  // Send all errors to webpack
+                  compilation.errors.push(...errors);
+                }
+                callback();
+              }
+            });
+          });
+        });
+      });
+    } else {
+      compiler.hooks.normalModuleFactory.tap('CaseSensitivePathsPlugin', (nmf) => {
+        nmf.hooks.afterResolve.tapAsync('CaseSensitivePathsPlugin', onAfterResolve);
+      });
+    }
   } else {
     compiler.plugin('done', onDone);
     compiler.plugin('normal-module-factory', (nmf) => {