Fix String.prototype.substr for zero length strings

dynjs · Sep 25, 2014 · fffbe0c · fffbe0c
1 parent 5025633
commit fffbe0c
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Showing 2 changed files with 6 additions and 0 deletions.
diff --git a/src/main/java/org/dynjs/runtime/builtins/types/string/prototype/Substr.java b/src/main/java/org/dynjs/runtime/builtins/types/string/prototype/Substr.java
@@ -25,6 +25,7 @@ public Object call(ExecutionContext context, Object self, Object... args) {
             start = Math.max(chars+start, 0);
         }
         length = Math.min(Math.max(length, 0), chars-start);
+        if (length <= 0) return "";
         return s.substring(start, start+length);
     }
 

diff --git a/src/test/java/org/dynjs/runtime/builtins/types/BuiltinStringTest.java b/src/test/java/org/dynjs/runtime/builtins/types/BuiltinStringTest.java
@@ -359,6 +359,11 @@ public void testSubstr() {
         assertThat(eval("'boblanceqmx'.substr(0, 3)")).isEqualTo("bob");
     }
 
+    @Test
+    public void testSubstrZeroLength() {
+        assertThat(eval("''.substr(2, 0)")).isEqualTo("");
+    }
+
     @Test
     public void testSubstrFromEnd() {
         assertThat(eval("'boblanceqmx'.substr(-3)")).isEqualTo("qmx");