Avoid setting attributes out of range

Author: zacwest

Example/Tests/Tests/ZSWStringParserSpec.m

@@ -57,6 +57,30 @@
         mockOptions = [OCMockObject mockForClass:[ZSWTaggedStringOptions class]];
     });
 
+    it(@"should handle a tag with no strings", ^{
+        ZSWTaggedString *taggedString = [ZSWTaggedString stringWithString:@"<cattail down='true'></cattail>"];
+        
+        NSArray *tags;
+        [[mockOptions expect] _private_updateAttributedString:OCMOCK_ANY
+                                              updatedWithTags:[OCMArg capture:&tags]];
+        
+        NSError *error;
+        
+        id string = [[ZSWStringParser stringWithTaggedString:taggedString
+                                                     options:mockOptions
+                                                 returnClass:[NSAttributedString class]
+                                                       error:&error] string];
+        
+        expect(string).to.equal(@"");
+        expect(error).to.beNil();
+        expect(tags).to.haveCountOf(1);
+        
+        ZSWStringParserTag *tag = tags.firstObject;
+        expect(tag.tagName).to.equal(@"cattail");
+        expect(tag.tagRange.location).to.equal(0);
+        expect(tag.tagRange.length).to.equal(0);
+    });
+    
     it(@"should handle a string with no tags", ^{
         ZSWTaggedString *taggedString = [ZSWTaggedString stringWithString:@"no more timothy hay!"];
 

Example/Tests/Tests/ZSWTaggedStringOptionsSpec.m

@@ -331,6 +331,31 @@
 
         expect(string).to.equal([[NSAttributedString alloc] initWithString:@"santa claus" attributes:nil]);
     });
+
+    it(@"should handle empty string after tags are removed", ^{
+        // effectively this is "<blah><null></null></blah>"
+        ZSWTaggedStringOptions *options = [ZSWTaggedStringOptions optionsWithBaseAttributes:@{
+                                                                                              NSFontAttributeName: [UIFont systemFontOfSize:12.0]
+                                                                                              }];
+        NSMutableAttributedString *string = [[NSMutableAttributedString alloc] initWithString:@"" attributes:nil];
+        ZSWStringParserTag *tag1 = [[ZSWStringParserTag alloc] initWithTagName:@"null" startLocation:0];
+        [tag1 updateWithTag:[[ZSWStringParserTag alloc] initWithTagName:@"/null" startLocation:0]];
+
+        ZSWStringParserTag *tag2 = [[ZSWStringParserTag alloc] initWithTagName:@"blah" startLocation:0];
+        [tag2 updateWithTag:[[ZSWStringParserTag alloc] initWithTagName:@"/blah" startLocation:0]];
+        
+        [options setDynamicAttributes:^NSDictionary<NSAttributedStringKey,id> * _Nonnull(NSString * _Nonnull tagName, NSDictionary<NSString *,id> * _Nonnull tagAttributes, NSDictionary<NSAttributedStringKey,id> * _Nonnull existingStringAttributes) {
+            return @{ NSForegroundColorAttributeName: [UIColor redColor] };
+        } forTagName:@"null"];
+        
+        [options setAttributes:@{ NSForegroundColorAttributeName: [UIColor redColor] }
+                    forTagName:@"blah"];
+        
+        [options _private_updateAttributedString:string updatedWithTags:@[ tag1, tag2 ]];
+        
+        expect(string).to.equal([[NSAttributedString alloc] initWithString:@"" attributes:nil]);
+
+    });
 
     describe(@"when a string contains multiple of the same type", ^{
         __block ZSWTaggedStringOptions *options;

ZSWTaggedString/Classes/ZSWTaggedStringOptions.m

@@ -139,6 +139,14 @@ - (void)_private_updateAttributedString:(NSMutableAttributedString *)string
                updatedWithTags:(NSArray *)tags {
     NSParameterAssert([string isKindOfClass:[NSMutableAttributedString class]]);
 
+    if (string.length == 0) {
+        // For example, a string like '<blah></blah>' has no content, so we can 't
+        // adjust what's inside based on tags. All we can do is base attributes.
+        // For dynamic attributes below, we may end up calling out of bounds trying
+        // to get existing attributes at index 0, which doesn't exist.
+        return;
+    }
+    
     [string setAttributes:self.baseAttributes range:NSMakeRange(0, string.length)];
 
     ZSWTaggedStringAttribute *unknownTagWrapper = self._private_unknownTagWrapper;