Fix GFM table parser to handle dangling pipe correctly (fixes commonm…

…ark#255)

CHANGELOG.md

@@ -6,6 +6,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 This project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html),
 with the exception that 0.x versions can break between minor versions.
 
+## [Unreleased]
+### Fixed
+- A single pipe (optional whitespace) now ends a table instead of crashing or
+  being treated as an empty row, for consistency with GitHub (#255).
+
 ## [0.19.0] - 2022-06-02
 ### Added
 - YAML front matter extension: Limited support for single and double
@@ -362,6 +367,7 @@ Initial release of commonmark-java, a port of commonmark.js with extensions
 for autolinking URLs, GitHub flavored strikethrough and tables.
 
 
+[Unreleased]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.19.0...HEAD
 [0.19.0]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.18.2...commonmark-parent-0.19.0
 [0.18.2]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.18.1...commonmark-parent-0.18.2
 [0.18.1]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.18.0...commonmark-parent-0.18.1

commonmark-ext-gfm-tables/src/main/java/org/commonmark/ext/gfm/tables/internal/TableBlockParser.java

@@ -19,14 +19,16 @@ public class TableBlockParser extends AbstractBlockParser {
     private final List<SourceLine> rowLines = new ArrayList<>();
     private final List<TableCell.Alignment> columns;
 
+    private boolean canHaveLazyContinuationLines = true;
+
     private TableBlockParser(List<TableCell.Alignment> columns, SourceLine headerLine) {
         this.columns = columns;
         this.rowLines.add(headerLine);
     }
 
     @Override
     public boolean canHaveLazyContinuationLines() {
-        return true;
+        return canHaveLazyContinuationLines;
     }
 
     @Override
@@ -36,7 +38,17 @@ public Block getBlock() {
 
     @Override
     public BlockContinue tryContinue(ParserState state) {
-        if (Parsing.find('|', state.getLine().getContent(), 0) != -1) {
+        CharSequence content = state.getLine().getContent();
+        int pipe = Parsing.find('|', content, state.getNextNonSpaceIndex());
+        if (pipe != -1) {
+            if (pipe == state.getNextNonSpaceIndex()) {
+                // If we *only* have a pipe character (and whitespace), that is not a valid table row and ends the table.
+                if (Parsing.skipSpaceTab(content, pipe + 1, content.length()) == content.length()) {
+                    // We also don't want the pipe to be added via lazy continuation.
+                    canHaveLazyContinuationLines = false;
+                    return BlockContinue.none();
+                }
+            }
             return BlockContinue.atIndex(state.getIndex());
         } else {
             return BlockContinue.none();
@@ -128,7 +140,7 @@ private static List<SourceLine> split(SourceLine line) {
             // This row has leading/trailing pipes - skip the leading pipe
             cellStart = nonSpace + 1;
             // Strip whitespace from the end but not the pipe or we could miss an empty ("||") cell
-            int nonSpaceEnd = Parsing.skipSpaceTabBackwards(row, row.length() - 1, cellStart + 1);
+            int nonSpaceEnd = Parsing.skipSpaceTabBackwards(row, row.length() - 1, cellStart);
             cellEnd = nonSpaceEnd + 1;
         }
         List<SourceLine> cells = new ArrayList<>();

commonmark-ext-gfm-tables/src/test/java/org/commonmark/ext/gfm/tables/TablesTest.java

@@ -261,21 +261,21 @@ public void pipesOnOutsideZeroLengthHeaders() {
                         "-|-------------|-\n" +
                         "1|      2      |3",
                 "<table>\n" +
-                "<thead>\n" +
-                "<tr>\n" +
-                "<th></th>\n" +
-                "<th>center header</th>\n" +
-                "<th></th>\n" +
-                "</tr>\n" +
-                "</thead>\n" +
-                "<tbody>\n" +
-                "<tr>\n" +
-                "<td>1</td>\n" +
-                "<td>2</td>\n" +
-                "<td>3</td>\n" +
-                "</tr>\n" +
-                "</tbody>\n" +
-                "</table>\n");
+                        "<thead>\n" +
+                        "<tr>\n" +
+                        "<th></th>\n" +
+                        "<th>center header</th>\n" +
+                        "<th></th>\n" +
+                        "</tr>\n" +
+                        "</thead>\n" +
+                        "<tbody>\n" +
+                        "<tr>\n" +
+                        "<td>1</td>\n" +
+                        "<td>2</td>\n" +
+                        "<td>3</td>\n" +
+                        "</tr>\n" +
+                        "</tbody>\n" +
+                        "</table>\n");
     }
 
     @Test
@@ -664,6 +664,47 @@ public void issue142() {
                         "</table>\n");
     }
 
+    @Test
+    public void danglingPipe() {
+        assertRendering("Abc|Def\n" +
+                "---|---\n" +
+                "1|2\n" +
+                "|", "<table>\n" +
+                "<thead>\n" +
+                "<tr>\n" +
+                "<th>Abc</th>\n" +
+                "<th>Def</th>\n" +
+                "</tr>\n" +
+                "</thead>\n" +
+                "<tbody>\n" +
+                "<tr>\n" +
+                "<td>1</td>\n" +
+                "<td>2</td>\n" +
+                "</tr>\n" +
+                "</tbody>\n" +
+                "</table>\n" +
+                "<p>|</p>\n");
+
+        assertRendering("Abc|Def\n" +
+                "---|---\n" +
+                "1|2\n" +
+                "  |  ", "<table>\n" +
+                "<thead>\n" +
+                "<tr>\n" +
+                "<th>Abc</th>\n" +
+                "<th>Def</th>\n" +
+                "</tr>\n" +
+                "</thead>\n" +
+                "<tbody>\n" +
+                "<tr>\n" +
+                "<td>1</td>\n" +
+                "<td>2</td>\n" +
+                "</tr>\n" +
+                "</tbody>\n" +
+                "</table>\n" +
+                "<p>|</p>\n");
+    }
+
     @Test
     public void attributeProviderIsApplied() {
         AttributeProviderFactory factory = new AttributeProviderFactory() {
@@ -718,7 +759,7 @@ public void sourceSpans() {
 
         TableBlock block = (TableBlock) document.getFirstChild();
         assertEquals(Arrays.asList(SourceSpan.of(0, 0, 7), SourceSpan.of(1, 0, 7),
-                SourceSpan.of(2, 0, 4), SourceSpan.of(3, 0, 8), SourceSpan.of(4, 0, 3)),
+                        SourceSpan.of(2, 0, 4), SourceSpan.of(3, 0, 8), SourceSpan.of(4, 0, 3)),
                 block.getSourceSpans());
 
         TableHead head = (TableHead) block.getFirstChild();