QTextMarkdownImporter::import(): don't crash if file has only yaml

If a markdown file has FrontMatter, we look for the end of the newlines
after the `---` marker to begin parsing the actual markdown. But check
bounds in case the file contains only front matter and not markdown.

Fixes: QTBUG-122982
Change-Id: I09c4ae90c47ebd84877738aecc1d1cad0b0bfca2
Reviewed-by: Anton Kudryavtsev <[email protected]>
Reviewed-by: Axel Spoerl <[email protected]>

3 files changed, 22 insertions, 3 deletions

diff --git a/src/gui/text/qtextmarkdownimporter.cpp b/src/gui/text/qtextmarkdownimporter.cpp
index c9aac01fa92..511c0883a4c 100644
--- a/src/gui/text/qtextmarkdownimporter.cpp
+++ b/src/gui/text/qtextmarkdownimporter.cpp
@@ -148,7 +148,7 @@ void QTextMarkdownImporter::import(const QString &markdown)
                 ++firstLinePos;
             QByteArray frontMatter = md.sliced(firstLinePos, endMarkerPos - firstLinePos);
             firstLinePos = endMarkerPos + 4; // first line of markdown after yaml
-            while (md.at(firstLinePos) == '\n' || md.at(firstLinePos) == '\r')
+            while (md.size() > firstLinePos && (md.at(firstLinePos) == '\n' || md.at(firstLinePos) == '\r'))
                 ++firstLinePos;
             md.remove(0, firstLinePos);
             doc->setMetaInformation(QTextDocument::FrontMatter, QString::fromUtf8(frontMatter));
diff --git a/tests/auto/gui/text/qtextmarkdownimporter/data/yaml-only.md b/tests/auto/gui/text/qtextmarkdownimporter/data/yaml-only.md
new file mode 100644
index 00000000000..1eff4db37f0
--- /dev/null
+++ b/tests/auto/gui/text/qtextmarkdownimporter/data/yaml-only.md
@@ -0,0 +1,6 @@
+---
+name: "Space"
+title: "Outer space"
+keywords:
+  - astronomy
+---
diff --git a/tests/auto/gui/text/qtextmarkdownimporter/tst_qtextmarkdownimporter.cpp b/tests/auto/gui/text/qtextmarkdownimporter/tst_qtextmarkdownimporter.cpp
index 53fa8274462..645dd9c102a 100644
--- a/tests/auto/gui/text/qtextmarkdownimporter/tst_qtextmarkdownimporter.cpp
+++ b/tests/auto/gui/text/qtextmarkdownimporter/tst_qtextmarkdownimporter.cpp
@@ -44,6 +44,7 @@ private slots:
     void pathological();
     void fencedCodeBlocks_data();
     void fencedCodeBlocks();
+    void frontMatter_data();
     void frontMatter();
 
 private:
@@ -634,9 +635,21 @@ void tst_QTextMarkdownImporter::fencedCodeBlocks()
     QCOMPARE(doc.toMarkdown(), rewrite);
 }
 
+void tst_QTextMarkdownImporter::frontMatter_data()
+{
+    QTest::addColumn<QString>("inputFile");
+    QTest::addColumn<int>("expectedBlockCount");
+
+    QTest::newRow("yaml + markdown") << QFINDTESTDATA("data/yaml.md") << 1;
+    QTest::newRow("yaml only") << QFINDTESTDATA("data/yaml-only.md") << 0;
+}
+
 void tst_QTextMarkdownImporter::frontMatter()
 {
-    QFile f(QFINDTESTDATA("data/yaml.md"));
+    QFETCH(QString, inputFile);
+    QFETCH(int, expectedBlockCount);
+
+    QFile f(inputFile);
     QVERIFY(f.open(QFile::ReadOnly | QIODevice::Text));
     QString md = QString::fromUtf8(f.readAll());
     f.close();
@@ -652,7 +665,7 @@ void tst_QTextMarkdownImporter::frontMatter()
         if (!iterator.currentBlock().text().isEmpty())
             ++blockCount;
     }
-    QCOMPARE(blockCount, 1); // yaml is not part of the markdown text
+    QCOMPARE(blockCount, expectedBlockCount); // yaml is not part of the markdown text
     QCOMPARE(doc.metaInformation(QTextDocument::FrontMatter), yaml); // without fences
 }