Merge pull request #339 from commonmark/issue-337-lazy-continuation-l…

…ine-source-span

Fix source spans of blocks with lazy continuation lines

commonmark/src/main/java/org/commonmark/internal/DocumentParser.java

@@ -288,7 +288,7 @@ private void parseLine(String ln) {
         // What remains at the offset is a text line. Add the text to the
         // appropriate block.
 
-        // First check for a lazy paragraph continuation:
+        // First check for a lazy continuation line
         if (!startedNewBlock && !isBlank() &&
                 getActiveBlockParser().canHaveLazyContinuationLines()) {
             openBlockParsers.get(openBlockParsers.size() - 1).sourceIndex = lastIndex;
@@ -441,10 +441,12 @@ private void addLine() {
 
     private void addSourceSpans() {
         if (includeSourceSpans != IncludeSourceSpans.NONE) {
-            // Don't add source spans for Document itself (it would get the whole source text)
+            // Don't add source spans for Document itself (it would get the whole source text), so start at 1, not 0
             for (int i = 1; i < openBlockParsers.size(); i++) {
-                OpenBlockParser openBlockParser = openBlockParsers.get(i);
-                int blockIndex = openBlockParser.sourceIndex;
+                var openBlockParser = openBlockParsers.get(i);
+                // In case of a lazy continuation line, the index is less than where the block parser would expect the
+                // contents to start, so let's use whichever is smaller.
+                int blockIndex = Math.min(openBlockParser.sourceIndex, index);
                 int length = line.getContent().length() - blockIndex;
                 if (length != 0) {
                     openBlockParser.blockParser.addSourceSpan(SourceSpan.of(lineIndex, blockIndex, length));

commonmark/src/test/java/org/commonmark/test/SourceSpansTest.java

@@ -204,6 +204,66 @@ public void linkReferenceDefinitionHeading() {
         assertEquals(List.of(SourceSpan.of(1, 0, 7), SourceSpan.of(2, 0, 3)), heading.getSourceSpans());
     }
 
+    @Test
+    public void lazyContinuationLines() {
+        {
+            // From https://spec.commonmark.org/0.31.2/#example-250
+            // Wrong source span for the inner block quote for the second line.
+            var doc = PARSER.parse("> > > foo\nbar\n");
+
+            var bq1 = (BlockQuote) doc.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 0, 9), SourceSpan.of(1, 0, 3)), bq1.getSourceSpans());
+            var bq2 = (BlockQuote) bq1.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 2, 7), SourceSpan.of(1, 0, 3)), bq2.getSourceSpans());
+            var bq3 = (BlockQuote) bq2.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 4, 5), SourceSpan.of(1, 0, 3)), bq3.getSourceSpans());
+            var paragraph = (Paragraph) bq3.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 6, 3), SourceSpan.of(1, 0, 3)), paragraph.getSourceSpans());
+        }
+
+        {
+            // Adding one character to the last line remove blockQuote3 source for the second line
+            var doc = PARSER.parse("> > > foo\nbars\n");
+
+            var bq1 = (BlockQuote) doc.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 0, 9), SourceSpan.of(1, 0, 4)), bq1.getSourceSpans());
+            var bq2 = (BlockQuote) bq1.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 2, 7), SourceSpan.of(1, 0, 4)), bq2.getSourceSpans());
+            var bq3 = (BlockQuote) bq2.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 4, 5), SourceSpan.of(1, 0, 4)), bq3.getSourceSpans());
+            var paragraph = (Paragraph) bq3.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 6, 3), SourceSpan.of(1, 0, 4)), paragraph.getSourceSpans());
+        }
+
+        {
+            // From https://spec.commonmark.org/0.31.2/#example-292
+            var doc = PARSER.parse("> 1. > Blockquote\ncontinued here.");
+
+            var bq1 = (BlockQuote) doc.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 0, 17), SourceSpan.of(1, 0, 15)), bq1.getSourceSpans());
+            var orderedList = (OrderedList) bq1.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 2, 15), SourceSpan.of(1, 0, 15)), orderedList.getSourceSpans());
+            var listItem = (ListItem) orderedList.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 2, 15), SourceSpan.of(1, 0, 15)), listItem.getSourceSpans());
+            var bq2 = (BlockQuote) listItem.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 5, 12), SourceSpan.of(1, 0, 15)), bq2.getSourceSpans());
+            var paragraph = (Paragraph) bq2.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 7, 10), SourceSpan.of(1, 0, 15)), paragraph.getSourceSpans());
+        }
+
+        {
+            // Lazy continuation line for nested blockquote
+            var doc = PARSER.parse("> > foo\n> bar\n");
+
+            var bq1 = (BlockQuote) doc.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 0, 7), SourceSpan.of(1, 0, 5)), bq1.getSourceSpans());
+            var bq2 = (BlockQuote) bq1.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 2, 5), SourceSpan.of(1, 2, 3)), bq2.getSourceSpans());
+            var paragraph = (Paragraph) bq2.getLastChild();
+            assertEquals(List.of(SourceSpan.of(0, 4, 3), SourceSpan.of(1, 2, 3)), paragraph.getSourceSpans());
+        }
+    }
+
     @Test
     public void visualCheck() {
         assertEquals("(> {[* <foo>]})\n(> {[  <bar>]})\n(> {⸢* ⸤baz⸥⸣})\n",