QTextMarkdownWriter: escape special characters (line or word prefix)

Try to avoid writing anything that the parser would misinterpret.
Escape pre-existing backslashes, but not those that are already escaped.
Optimize maybeEscapeFirstChar() slightly and apply it to every line
of output (except in code blocks), not only to new lines created by
word-wrapping.

Since it would be hard to do this without using regular expressions,
the markdown writer feature now depends on the regex feature.

Fixes: QTBUG-96051
Fixes: QTBUG-122083
Pick-to: 6.7
Change-Id: I8d95366501fd31441829081c668f11a3a3a23fe2
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 62 insertions, 4 deletions

diff --git a/tests/auto/gui/text/qtextmarkdownwriter/tst_qtextmarkdownwriter.cpp b/tests/auto/gui/text/qtextmarkdownwriter/tst_qtextmarkdownwriter.cpp
index 3c51ccdff8..d0ae34d67d 100644
--- a/tests/auto/gui/text/qtextmarkdownwriter/tst_qtextmarkdownwriter.cpp
+++ b/tests/auto/gui/text/qtextmarkdownwriter/tst_qtextmarkdownwriter.cpp
@@ -45,6 +45,8 @@ private slots:
     void rewriteDocument();
     void fromHtml_data();
     void fromHtml();
+    void escapeSpecialCharacters_data();
+    void escapeSpecialCharacters();
 
 private:
     bool isMainFontFixed();
@@ -822,16 +824,21 @@ void tst_QTextMarkdownWriter::fromHtml_data()
     QTest::newRow("code") <<
         "<pre class=\"language-pseudocode\">\n#include \"foo.h\"\n\nblock {\n    statement();\n}\n\n</pre>" <<
         "```pseudocode\n#include \"foo.h\"\n\nblock {\n    statement();\n}\n\n```\n\n";
-    // TODO
-//    QTest::newRow("escaped number and paren after double newline") <<
-//        "<p>(The first sentence of this paragraph is a line, the next paragraph has a number</p>13) but that's not part of an ordered list" <<
-//        "(The first sentence of this paragraph is a line, the next paragraph has a number\n\n13\\) but that's not part of an ordered list\n\n";
+    QTest::newRow("escaped number and paren after single newline") <<
+        "<p>(The first sentence of this paragraph is a line, next paragraph has a number 13) but that's not part of an ordered list</p>" <<
+        "(The first sentence of this paragraph is a line, next paragraph has a number\n13\\) but that's not part of an ordered list\n\n";
+    QTest::newRow("escaped number and paren after double newline") <<
+        "<p>(The first sentence of this paragraph is a line, the next paragraph has a number</p>13) but that's not part of an ordered list" <<
+        "(The first sentence of this paragraph is a line, the next paragraph has a number\n\n13\\) but that's not part of an ordered list\n\n";
     QTest::newRow("preformats with embedded backticks") <<
         "<pre>none `one` ``two``</pre>plain<pre>```three``` ````four````</pre>plain" <<
         "```\nnone `one` ``two``\n\n```\nplain\n\n```\n```three``` ````four````\n\n```\nplain\n\n";
     QTest::newRow("list items with and without checkboxes") <<
         "<ul><li>bullet</li><li class=\"unchecked\">unchecked item</li><li class=\"checked\">checked item</li></ul>" <<
         "- bullet\n- [ ] unchecked item\n- [x] checked item\n";
+    QTest::newRow("table with backslash in cell") << // QTBUG-96051
+            "<table><tr><td>1011011 [</td><td>1011100 backslash \\</td></tr></table>" <<
+            "|1011011 [|1011100 backslash \\\\|";
 }
 
 void tst_QTextMarkdownWriter::fromHtml()
@@ -858,5 +865,56 @@ void tst_QTextMarkdownWriter::fromHtml()
     QCOMPARE(output, expectedOutput);
 }
 
+void tst_QTextMarkdownWriter::escapeSpecialCharacters_data()
+{
+    QTest::addColumn<QString>("input");
+    QTest::addColumn<QString>("expectedOutput");
+
+    QTest::newRow("backslash") << "foo \\ bar \\\\ baz \\" << "foo \\\\ bar \\\\ baz \\\\";
+    QTest::newRow("not emphasized") << "*normal* **normal too**" << "\\*normal* \\**normal too**";
+    QTest::newRow("not code") << "`normal` `normal too`" << "\\`normal` \\`normal too`";
+    QTest::newRow("code fence") << "```not a fence; ``` no risk here; ```not a fence" // TODO slightly inconsistent
+                                << "\\```not a fence; ``` no risk here; \\```not a fence";
+    QTest::newRow("not html") << "<p>not a tag: <br/> nope</p>" << "\\<p>not a tag: \\<br/> nope\\</p>";
+    QTest::newRow("not a link") << "text [not a link](/foo)" << "text \\[not a link](/foo)";
+    QTest::newRow("not a circle") << "* polaris" << "\\* polaris";
+    QTest::newRow("not a square") << "+ groovy" << "\\+ groovy";
+    QTest::newRow("not a bullet") << "- stayin alive" << "\\- stayin alive";
+    QTest::newRow("arithmetic") << "1 + 2 - 3 * 4" << "1 + 2 - 3 * 4";
+    QTest::newRow("not a list") << "1. not a list" << "1\\. not a list";
+    QTest::newRow("not a list either") << "Jupiter and 10." << "Jupiter and 10.";
+    QTest::newRow("not a heading") << "# not a heading" << "\\# not a heading";
+    QTest::newRow("a non-entity") << "&ouml; not a character entity" << "\\&ouml; not a character entity";
+}
+
+/*! \internal
+    If the user types into a Qt-based editor plain text that the
+    markdown parser would misinterpret, escape it when we save to markdown
+    to clarify that it's plain text.
+    https://spec.commonmark.org/0.31.2/#backslash-escapes
+*/
+void tst_QTextMarkdownWriter::escapeSpecialCharacters() // QTBUG-96051, QTBUG-122083
+{
+    QFETCH(QString, input);
+    QFETCH(QString, expectedOutput);
+
+    document->setPlainText(input);
+    QString output = documentToUnixMarkdown();
+
+#ifdef DEBUG_WRITE_OUTPUT
+    {
+        QFile out("/tmp/" + QLatin1String(QTest::currentDataTag()) + ".md");
+        out.open(QFile::WriteOnly);
+        out.write(output.toUtf8());
+        out.close();
+    }
+#endif
+
+    output = output.trimmed();
+    if (output != expectedOutput && (isMainFontFixed() || isFixedFontProportional()))
+        QEXPECT_FAIL("", "fixed main font or proportional fixed font (QTBUG-103484)", Continue);
+    QCOMPARE(output, expectedOutput);
+}
+
 QTEST_MAIN(tst_QTextMarkdownWriter)
 #include "tst_qtextmarkdownwriter.moc"