Merge pull request #101 from mdiep/infinite-list-loop

Fix infinite loop in list parsing
mdiep · Apr 19, 2016 · 07b9952 · 07b9952
2 parents b05594c + 46fb011
commit 07b9952
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Showing 3 changed files with 45 additions and 32 deletions.
diff --git a/Source/MMParser.m b/Source/MMParser.m
@@ -268,7 +268,7 @@ - (MMElement *)_parseBlockElementWithScanner:(MMScanner *)scanner
         return element;
 
     [scanner beginTransaction];
-    element = [self _parseListWithScanner:scanner atIndentationLevel:0];
+    element = [self _parseListWithScanner:scanner];
     [scanner commitTransaction:element != nil];
     if (element)
         return element;
@@ -515,7 +515,7 @@ - (NSArray *)_parseCodeLinesWithScanner:(MMScanner *)scanner
             // Add a newline
             MMElement *newline = [MMElement new];
             newline.type  = MMElementTypeNone;
-            newline.range = NSMakeRange(0, 0);
+            newline.range = NSMakeRange(scanner.location, 0);
             [children addObject:newline];
         }
     }
@@ -541,7 +541,7 @@ - (MMElement *)_parseCodeBlockWithScanner:(MMScanner *)scanner
         NSUInteger numOfEmptyLines = [scanner skipEmptyLines];
         for (NSUInteger idx=0; idx<numOfEmptyLines; idx++)
         {
-            [element addInnerRange:NSMakeRange(0, 0)];
+            [element addInnerRange:NSMakeRange(scanner.location, 0)];
         }
 
         // Need 4 spaces to continue the code block
@@ -729,7 +729,7 @@ - (BOOL)_parseListMarkerWithScanner:(MMScanner *)scanner
     return NO;
 }
 
-- (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel:(NSUInteger)level
+- (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner
 {
     BOOL canContainBlocks = NO;
 
@@ -738,18 +738,7 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
         canContainBlocks = YES;
     }
 
-    // Make sure there's enough leading space
-    [scanner beginTransaction];
-    NSUInteger toSkip  = 4 * level;
-    NSUInteger skipped = [scanner skipIndentationUpTo:toSkip];
-    if (skipped != toSkip)
-    {
-        [scanner commitTransaction:NO];
-        return nil;
-    }
-    [scanner commitTransaction:YES];
-
-    [scanner skipIndentationUpTo:3]; // Additional optional space
+    [scanner skipIndentationUpTo:3]; // Optional space
 
     BOOL foundAnItem = [self _parseListMarkerWithScanner:scanner];
     if (!foundAnItem)
@@ -781,7 +770,7 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
 
         // Check for the start of a new list item
         [scanner beginTransaction];
-        [scanner skipIndentationUpTo:4*level + 3];
+        [scanner skipIndentationUpTo:3];
         BOOL newMarker = [self _parseListMarkerWithScanner:scanner];
         [scanner commitTransaction:NO];
         if (newMarker)
@@ -796,13 +785,13 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
 
         // Check for a nested list
         [scanner beginTransaction];
-        [scanner skipIndentationUpTo:4*(level + 1) + 3];
+        [scanner skipIndentationUpTo:4 + 3];
         [scanner beginTransaction];
         BOOL newList = [self _parseListMarkerWithScanner:scanner];
         [scanner commitTransaction:NO];
         if (newList && nestedListIndex == NSNotFound)
         {
-            [element addInnerRange:NSMakeRange(0, 0)];
+            [element addInnerRange:NSMakeRange(scanner.location, 0)];
             nestedListIndex = element.innerRanges.count;
             [element addInnerRange:scanner.currentRange];
 
@@ -817,9 +806,8 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
         {
             // Must be 4 spaces past the indentation level to start a new paragraph
             [scanner beginTransaction];
-            NSUInteger newLevel    = 4*(1+level);
-            NSUInteger indentation = [scanner skipIndentationUpTo:newLevel];
-            if (indentation < newLevel)
+            NSUInteger indentation = [scanner skipIndentationUpTo:4];
+            if (indentation < 4)
             {
                 [scanner commitTransaction:NO];
                 [scanner commitTransaction:NO];
@@ -828,7 +816,7 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
             [scanner commitTransaction:YES];
             [scanner commitTransaction:YES];
 
-            [element addInnerRange:NSMakeRange(0, 0)];
+            [element addInnerRange:NSMakeRange(scanner.location, 0)];
             canContainBlocks = YES;
         }
         else
@@ -837,7 +825,7 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
 
             // Don't skip past where a nested list would start because that list
             // could have its own nested list, so the whitespace will be needed.
-            [scanner skipIndentationUpTo:4*(level + 1)];
+            [scanner skipIndentationUpTo:4];
         }
 
         if (nestedListIndex != NSNotFound)
@@ -890,20 +878,17 @@ - (MMElement *)_parseListItemWithScanner:(MMScanner *)scanner atIndentationLevel
     return element;
 }
 
-- (MMElement *)_parseListWithScanner:(MMScanner *)scanner atIndentationLevel:(NSUInteger)level
+- (MMElement *)_parseListWithScanner:(MMScanner *)scanner
 {
     [scanner beginTransaction];
-    // Check the amount of leading whitespace
-    NSUInteger toSkip  = 4 * level;
-    NSUInteger skipped = [scanner skipIndentationUpTo:toSkip];
 
-    [scanner skipIndentationUpTo:3]; // Additional optional space
+    [scanner skipIndentationUpTo:3]; // Optional space
     unichar nextChar   = scanner.nextCharacter;
     BOOL    isBulleted = (nextChar == '*' || nextChar == '-' || nextChar == '+');
     BOOL    hasMarker  = [self _parseListMarkerWithScanner:scanner];
     [scanner commitTransaction:NO];
 
-    if (toSkip != skipped || !hasMarker)
+    if (!hasMarker)
         return nil;
 
     MMElement *element = [MMElement new];
@@ -922,7 +907,7 @@ - (MMElement *)_parseListWithScanner:(MMScanner *)scanner atIndentationLevel:(NS
             break;
 
         [scanner beginTransaction];
-        MMElement *item = [self _parseListItemWithScanner:scanner atIndentationLevel:level];
+        MMElement *item = [self _parseListItemWithScanner:scanner];
         if (!item)
         {
             [scanner commitTransaction:NO];

diff --git a/Source/MMScanner.m b/Source/MMScanner.m
@@ -280,7 +280,7 @@ - (NSUInteger)skipEmptyLines
     {
         [self beginTransaction];
         [self skipWhitespace];
-        if (![self atEndOfLine])
+        if (!self.atEndOfLine)
         {
             [self commitTransaction:NO];
             break;

diff --git a/Tests/MMListTests.m b/Tests/MMListTests.m
@@ -299,6 +299,34 @@ - (void)testNestedLists_trailingNested
     MMAssertMarkdownEqualsHTML(markdown, html);
 }
 
+- (void)testNestedListWithMultipleEmptyLinesAndBacktracking
+{
+    // https://github.com/mdiep/MMMarkdown/issues/100
+    NSString *markdown =
+        @"* A\n"
+         "    * B\n"
+         "\n"
+         "    * C\n"
+         "\n"
+         "    D\n";
+    NSString *html =
+        @"<ul>\n"
+         "<li>\n"
+         "<p>A</p>\n"
+         "<ul>\n"
+         "<li>\n"
+         "<p>B</p>\n"
+         "</li>\n"
+         "<li>\n"
+         "<p>C</p>\n"
+         "</li>\n"
+         "</ul>\n"
+         "<p>D</p>\n"
+         "</li>\n"
+         "</ul>";
+    MMAssertMarkdownEqualsHTML(markdown, html);
+}
+
 - (void)testList_followedByHorizontalRule
 {
     NSString *markdown = @"* One\n"