Performance Optimization:

- Avoid backtracking during the parsing of annotations. Part of #115
jhipster · Jan 8, 2019 · 73a888d · 73a888d
1 parent 8c92539
commit 73a888d
Show file tree

Hide file tree

Showing 4 changed files with 24 additions and 40 deletions.
diff --git a/packages/java-parser/scripts/parse-samples.js b/packages/java-parser/scripts/parse-samples.js
@@ -27,6 +27,7 @@ let failed = 0;
 
 const fullStartTime = new Date().getTime();
 javaSampleFiles.forEach(fileDesc => {
+  // TODO: read the files BEFORE the benchmark started to only bench the parsing speed...
   const currJavaFileString = fs.readFileSync(fileDesc.path, "utf8");
   const relativePath = path.relative(__dirname, fileDesc.path);
   try {

diff --git a/packages/java-parser/scripts/single-sample-runner.js b/packages/java-parser/scripts/single-sample-runner.js
@@ -6,6 +6,10 @@
 
 const javaParserChev = require("../src/index");
 
-const input = `private int to;`;
+const input = `  @RequestMapping("/product")
+  public Void put(String key, Object value) {
+    properties.put(key, value);
+    return null;
+  }`;
 
 javaParserChev.parse(input, "classBodyDeclaration");
diff --git a/packages/java-parser/src/parser.js b/packages/java-parser/src/parser.js
@@ -42,9 +42,6 @@ class JavaParser extends Parser {
       maxLookahead: 2,
       // ambiguities resolved by backtracking
       ignoredIssues: {
-        annotation: {
-          OR: true
-        },
         annotationTypeMemberDeclaration: {
           OR: true
         },

diff --git a/packages/java-parser/src/productions/interfaces.js b/packages/java-parser/src/productions/interfaces.js
@@ -238,31 +238,28 @@ function defineRules($, t) {
 
   // https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-Annotation
   $.RULE("annotation", () => {
-    // TODO: performance optimization: implement optimized backtracking here.
-    $.OR([
-      {
-        GATE: $.BACKTRACK($.normalAnnotation),
-        ALT: () => $.SUBRULE($.normalAnnotation)
-      },
-      // "singleElementAnnotation" must appear before "markerAnnotation" due to common
-      // prefix.
-      {
-        GATE: $.BACKTRACK($.singleElementAnnotation),
-        ALT: () => $.SUBRULE($.singleElementAnnotation)
-      },
-      { ALT: () => $.SUBRULE($.markerAnnotation) }
-    ]);
-  });
-
-  // https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-NormalAnnotation
-  $.RULE("normalAnnotation", () => {
+    // Spec Deviation: The common prefix for all three annotation types was extracted to this rule.
+    // This was done to avoid the use of backtracking for performance reasons.
     $.CONSUME(t.At);
     $.SUBRULE($.typeName);
-    $.CONSUME(t.LBrace);
+
+    // If this optional grammar was not invoked we have a markerAnnotation
+    // https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-MarkerAnnotation
     $.OPTION(() => {
-      $.SUBRULE($.elementValuePairList);
+      $.CONSUME(t.LBrace);
+      $.OR([
+        // normal annotation - https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-NormalAnnotation
+        { ALT: () => $.SUBRULE($.elementValuePairList) },
+        // Single Element Annotation - https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-SingleElementAnnotation
+        { ALT: () => $.SUBRULE($.elementValue) },
+        {
+          ALT: () => {
+            /* empty normal annotation contents */
+          }
+        }
+      ]);
+      $.CONSUME(t.RBrace);
     });
-    $.CONSUME(t.RBrace);
   });
 
   // https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-ElementValuePairList
@@ -321,21 +318,6 @@ function defineRules($, t) {
     });
   });
 
-  // https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-MarkerAnnotation
-  $.RULE("markerAnnotation", () => {
-    $.CONSUME(t.At);
-    $.SUBRULE($.typeName);
-  });
-
-  // https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-SingleElementAnnotation
-  $.RULE("singleElementAnnotation", () => {
-    $.CONSUME(t.At);
-    $.SUBRULE($.typeName);
-    $.CONSUME(t.LBrace);
-    $.SUBRULE($.elementValue);
-    $.CONSUME(t.RBrace);
-  });
-
   // ------------------------------------
   // Special optimized backtracking rules.
   // ------------------------------------