Support Java 8+ semantics for String.split()

Fixes gwtproject#8868
niloc132 · Dec 8, 2024 · 6079779 · 6079779
1 parent c2229e7
commit 6079779
Show file tree

Hide file tree

Showing 2 changed files with 14 additions and 5 deletions.
diff --git a/user/super/com/google/gwt/emul/java/lang/String.java b/user/super/com/google/gwt/emul/java/lang/String.java
@@ -647,10 +647,22 @@ public String[] split(String regex, int maxMatch) {
       // subgroup handling
       NativeRegExp.Match matchObj = compiled.exec(trail);
       if (matchObj == null || trail == "" || (count == (maxMatch - 1) && maxMatch > 0)) {
+        // At the end of the string, or we have performed the maximum number of matches,
+        // record the remaining string and break
         out[count] = trail;
         break;
       } else {
         int matchIndex = matchObj.getIndex();
+
+        if (lastTrail == null && matchIndex == 0) {
+          // As of Java 8, we should discard the first zero-length match if it is the beginning of
+          // the string. Do not increment the count, and do not add to the output array.
+          trail = trail.substring(matchIndex + matchObj.asArray()[0].length(), trail.length());
+          compiled.lastIndex = 0;
+          lastTrail = trail;
+          continue;
+        }
+
         out[count] = trail.substring(0, matchIndex);
         trail = trail.substring(matchIndex + matchObj.asArray()[0].length(), trail.length());
         // Force the compiled pattern to reset internal state

diff --git a/user/test/com/google/gwt/emultest/java/lang/StringTest.java b/user/test/com/google/gwt/emultest/java/lang/StringTest.java
@@ -789,11 +789,8 @@ public void testSplit() {
   }
 
   public void testSplit_emptyExpr() {
-    // TODO(rluble):  implement JDK8 string.split semantics and fix test.
-    String[] expected = (TestUtils.getJdkVersion() > 7) ?
-        new String[] {"a", "b", "c", "x", "x", "d", "e", "x", "f", "x"} :
-        new String[] {"", "a", "b", "c", "x", "x", "d", "e", "x", "f", "x"};
-    compareList("emptyRegexSplit", expected, "abcxxdexfx".split(""));
+    String[] expected = new String[] {"a", "b", "c", "x", "x", "d", "e", "x", "f", "x"};
+    compareList("emptyRegexSplit", expected, hideFromCompiler("abcxxdexfx").split(""));
   }
 
   public void testStartsWith() {