qdoc: Fix handling of default values for function parameters

When using an \fn command to document a function that has default
values for parameter(s), The Clang parser retrieves a relevant
section of the source file that contains the expression for the
default value. In case of \fn, the source is a temporary translation
unit that was constructed on the fly - but it may not exist anymore,
and the default value is lost.

Fix this by storing the contents of the temporary TU for later access.

Fixes: QTBUG-83472
Change-Id: I20ad9e3322636450db1def65933837c1c767f2c4
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

11 files changed, 45 insertions, 30 deletions

diff --git a/src/qdoc/clangcodeparser.cpp b/src/qdoc/clangcodeparser.cpp
index db9c2ed07..b5c6a8ac6 100644
--- a/src/qdoc/clangcodeparser.cpp
+++ b/src/qdoc/clangcodeparser.cpp
@@ -65,6 +65,9 @@ QT_BEGIN_NAMESPACE
 static CXTranslationUnit_Flags flags_ = static_cast<CXTranslationUnit_Flags>(0);
 static CXIndex index_ = nullptr;
 
+QByteArray ClangCodeParser::fn_;
+constexpr const char *fnDummyFileName = "/fn_dummyfile.cpp";
+
 #ifndef QT_NO_DEBUG_STREAM
 template<class T>
 static QDebug operator<<(QDebug debug, const std::vector<T> &v)
@@ -199,11 +202,15 @@ static QString getSpelling(CXSourceRange range)
     unsigned int offset1, offset2;
     clang_getFileLocation(start, &file1, nullptr, nullptr, &offset1);
     clang_getFileLocation(end, &file2, nullptr, nullptr, &offset2);
+
     if (file1 != file2 || offset2 <= offset1)
         return QString();
     QFile file(fromCXString(clang_getFileName(file1)));
-    if (!file.open(QFile::ReadOnly))
+    if (!file.open(QFile::ReadOnly)) {
+        if (file.fileName() == fnDummyFileName)
+            return QString::fromUtf8(ClangCodeParser::fn().mid(offset1, offset2 - offset1));
         return QString();
+    }
     file.seek(offset1);
     return QString::fromUtf8(file.read(offset2 - offset1));
 }
@@ -1595,6 +1602,7 @@ void ClangCodeParser::parseSourceFile(const Location & /*location*/, const QStri
     clang_disposeTranslationUnit(tu);
     clang_disposeIndex(index_);
     namespaceScope_.clear();
+    fn_.clear();
 }
 
 /*!
@@ -1673,17 +1681,17 @@ Node *ClangCodeParser::parseFnArg(const Location &location, const QString &fnArg
         args.push_back(pchName_.constData());
     }
     CXTranslationUnit tu;
-    QByteArray fn;
+    fn_.clear();
     for (const auto &ns : qAsConst(namespaceScope_))
-        fn.prepend("namespace " + ns.toUtf8() + " {");
-    fn += fnArg.toUtf8();
-    if (!fn.endsWith(";"))
-        fn += "{ }";
-    fn.append(namespaceScope_.size(), '}');
-
-    const char *dummyFileName = "/fn_dummyfile.cpp";
-    CXUnsavedFile unsavedFile { dummyFileName, fn.constData(),
-                                static_cast<unsigned long>(fn.size()) };
+        fn_.prepend("namespace " + ns.toUtf8() + " {");
+    fn_ += fnArg.toUtf8();
+    if (!fn_.endsWith(";"))
+        fn_ += "{ }";
+    fn_.append(namespaceScope_.size(), '}');
+
+    const char *dummyFileName = fnDummyFileName;
+    CXUnsavedFile unsavedFile { dummyFileName, fn_.constData(),
+                                static_cast<unsigned long>(fn_.size()) };
     CXErrorCode err = clang_parseTranslationUnit2(index, dummyFileName, args.data(), args.size(),
                                                   &unsavedFile, 1, flags, &tu);
     qCDebug(lcQdoc) << __FUNCTION__ << "clang_parseTranslationUnit2(" << dummyFileName << args
diff --git a/src/qdoc/clangcodeparser.h b/src/qdoc/clangcodeparser.h
index 9af292e67..1575d31fb 100644
--- a/src/qdoc/clangcodeparser.h
+++ b/src/qdoc/clangcodeparser.h
@@ -62,6 +62,7 @@ public:
     void parseSourceFile(const Location &location, const QString &filePath) override;
     void precompileHeaders() override;
     Node *parseFnArg(const Location &location, const QString &fnArg) override;
+    static const QByteArray &fn() { return fn_; }
 
 private:
     void getDefaultArgs();
@@ -79,6 +80,7 @@ private:
     std::vector<const char *> args_;
     QVector<QByteArray> moreArgs_;
     QStringList namespaceScope_;
+    static QByteArray fn_;
 };
 
 QT_END_NAMESPACE
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/docbook/testqdoc-test.xml b/tests/auto/qdoc/generatedoutput/expected_output/docbook/testqdoc-test.xml
index ad6a4f30f..76025b06e 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/docbook/testqdoc-test.xml
+++ b/tests/auto/qdoc/generatedoutput/expected_output/docbook/testqdoc-test.xml
@@ -63,13 +63,14 @@
 <db:para>An inline function, documented using the \fn QDoc command.</db:para>
 </db:section>
 <db:section xml:id="someFunction">
-<db:title>Test::int someFunction(int <db:emphasis>v</db:emphasis>)</db:title>
+<db:title>Test::int someFunction(int <db:emphasis>v</db:emphasis> = 0)</db:title>
 <db:methodsynopsis>
 <db:type>int</db:type>
 <db:methodname>someFunction</db:methodname>
 <db:methodparam>
 <db:type>int</db:type>
 <db:parameter>v</db:parameter>
+<db:initializer>0</db:initializer>
 </db:methodparam>
 <db:synopsisinfo db:role="meta">plain</db:synopsisinfo>
 <db:synopsisinfo db:role="signature">int someFunction(int v)</db:synopsisinfo>
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/html/testqdoc-test.webxml b/tests/auto/qdoc/generatedoutput/expected_output/html/testqdoc-test.webxml
index d2726cc57..7ae77ec5a 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/html/testqdoc-test.webxml
+++ b/tests/auto/qdoc/generatedoutput/expected_output/html/testqdoc-test.webxml
@@ -39,7 +39,7 @@
                 <description/>
             </function>
             <function name="someFunction" fullname="TestQDoc::Test::someFunction" href="testqdoc-test.html#someFunction" status="active" access="public" location="testcpp.h" documented="true" meta="plain" virtual="non" const="false" static="false" final="false" override="false" type="int" signature="int someFunction(int v)">
-                <parameter type="int" name="v" default=""/>
+                <parameter type="int" name="v" default="0"/>
                 <description>
                     <para>Function that takes a parameter <argument>v</argument>. Also returns the value of <argument>v</argument>.</para>
                 </description>
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/ignoresince/testqdoc-test.html b/tests/auto/qdoc/generatedoutput/expected_output/ignoresince/testqdoc-test.html
index 52a10f706..0d4283a8f 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/ignoresince/testqdoc-test.html
+++ b/tests/auto/qdoc/generatedoutput/expected_output/ignoresince/testqdoc-test.html
@@ -34,7 +34,7 @@
 <h2 id="public-functions">Public Functions</h2>
 <div class="table"><table class="alignedsummary">
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#inlineFunction">inlineFunction</a></b>()</td></tr>
-<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i>)</td></tr>
+<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i> = 0)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunctionDefaultArg">someFunctionDefaultArg</a></b>(int <i>i</i>, bool <i>b</i> = false)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#virtualFun">virtualFun</a></b>()</td></tr>
 </table></div>
@@ -68,7 +68,7 @@
 <p>An inline function, documented using the \fn QDoc command.</p>
 <!-- @@@inlineFunction -->
 <!-- $$$someFunction[overload1]$$$someFunctionint -->
-<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i>)</h3>
+<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i> = 0)</h3>
 <p>Function that takes a parameter <i>v</i>. Also returns the value of <i>v</i>.</p>
 <p>This function was introduced in Test 1.0.</p>
 <!-- @@@someFunction -->
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/scopedenum/testqdoc-test.html b/tests/auto/qdoc/generatedoutput/expected_output/scopedenum/testqdoc-test.html
index 3fc1f2bc7..864205274 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/scopedenum/testqdoc-test.html
+++ b/tests/auto/qdoc/generatedoutput/expected_output/scopedenum/testqdoc-test.html
@@ -40,7 +40,7 @@
 <h2 id="public-functions">Public Functions</h2>
 <div class="table"><table class="alignedsummary">
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#inlineFunction">inlineFunction</a></b>()</td></tr>
-<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i>)</td></tr>
+<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i> = 0)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunctionDefaultArg">someFunctionDefaultArg</a></b>(int <i>i</i>, bool <i>b</i> = false)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#virtualFun">virtualFun</a></b>()</td></tr>
 </table></div>
@@ -85,7 +85,7 @@
 <p>An inline function, documented using the \fn QDoc command.</p>
 <!-- @@@inlineFunction -->
 <!-- $$$someFunction[overload1]$$$someFunctionint -->
-<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i>)</h3>
+<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i> = 0)</h3>
 <p>Function that takes a parameter <i>v</i>. Also returns the value of <i>v</i>.</p>
 <!-- @@@someFunction -->
 <!-- $$$someFunctionDefaultArg[overload1]$$$someFunctionDefaultArgintbool -->
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/template/testqdoc-test.html b/tests/auto/qdoc/generatedoutput/expected_output/template/testqdoc-test.html
index 4ec52916a..75643dede 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/template/testqdoc-test.html
+++ b/tests/auto/qdoc/generatedoutput/expected_output/template/testqdoc-test.html
@@ -34,7 +34,7 @@
 <h2 id="public-functions">Public Functions</h2>
 <div class="table"><table class="alignedsummary">
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#inlineFunction">inlineFunction</a></b>()</td></tr>
-<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i>)</td></tr>
+<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i> = 0)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunctionDefaultArg">someFunctionDefaultArg</a></b>(int <i>i</i>, bool <i>b</i> = false)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#virtualFun">virtualFun</a></b>()</td></tr>
 </table></div>
@@ -73,7 +73,7 @@
 <p>An inline function, documented using the \fn QDoc command.</p>
 <!-- @@@inlineFunction -->
 <!-- $$$someFunction[overload1]$$$someFunctionint -->
-<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i>)</h3>
+<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i> = 0)</h3>
 <p>Function that takes a parameter <i>v</i>. Also returns the value of <i>v</i>.</p>
 <!-- @@@someFunction -->
 <!-- $$$someFunctionDefaultArg[overload1]$$$someFunctionDefaultArgintbool -->
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/testcpp.index b/tests/auto/qdoc/generatedoutput/expected_output/testcpp.index
index ae997fa52..ae3b4a875 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/testcpp.index
+++ b/tests/auto/qdoc/generatedoutput/expected_output/testcpp.index
@@ -22,7 +22,7 @@
                     <parameter type="bool" name="b" default=""/>
                 </function>
                 <function name="someFunction" fullname="TestQDoc::Test::someFunction" href="testqdoc-test.html#someFunction" status="active" access="public" location="testcpp.h" documented="true" meta="plain" virtual="non" const="false" static="false" final="false" override="false" type="int" signature="int someFunction(int v)">
-                    <parameter type="int" name="v" default=""/>
+                    <parameter type="int" name="v" default="0"/>
                 </function>
                 <function name="someFunctionDefaultArg" fullname="TestQDoc::Test::someFunctionDefaultArg" href="testqdoc-test.html#someFunctionDefaultArg" status="active" access="public" location="testcpp.h" documented="true" meta="plain" virtual="non" const="false" static="false" final="false" override="false" type="void" signature="void someFunctionDefaultArg(int i, bool b)">
                     <parameter type="int" name="i" default=""/>
diff --git a/tests/auto/qdoc/generatedoutput/expected_output/testqdoc-test.html b/tests/auto/qdoc/generatedoutput/expected_output/testqdoc-test.html
index 84c0c4fe3..49066d0e6 100644
--- a/tests/auto/qdoc/generatedoutput/expected_output/testqdoc-test.html
+++ b/tests/auto/qdoc/generatedoutput/expected_output/testqdoc-test.html
@@ -34,7 +34,7 @@
 <h2 id="public-functions">Public Functions</h2>
 <div class="table"><table class="alignedsummary">
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#inlineFunction">inlineFunction</a></b>()</td></tr>
-<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i>)</td></tr>
+<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunction">someFunction</a></b>(int <i>v</i> = 0)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#someFunctionDefaultArg">someFunctionDefaultArg</a></b>(int <i>i</i>, bool <i>b</i> = false)</td></tr>
 <tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="testqdoc-test.html#virtualFun">virtualFun</a></b>()</td></tr>
 </table></div>
@@ -68,7 +68,7 @@
 <p>An inline function, documented using the \fn QDoc command.</p>
 <!-- @@@inlineFunction -->
 <!-- $$$someFunction[overload1]$$$someFunctionint -->
-<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i>)</h3>
+<h3 class="fn" id="someFunction"><a name="someFunction"></a><span class="type">int</span> Test::<span class="name">someFunction</span>(<span class="type">int</span> <i>v</i> = 0)</h3>
 <p>Function that takes a parameter <i>v</i>. Also returns the value of <i>v</i>.</p>
 <!-- @@@someFunction -->
 <!-- $$$someFunctionDefaultArg[overload1]$$$someFunctionDefaultArgintbool -->
diff --git a/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.cpp b/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.cpp
index 17045eed5..31b910fae 100644
--- a/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.cpp
+++ b/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.cpp
@@ -124,13 +124,7 @@ void Test::someFunctionDefaultArg(int i, bool b = false)
     return;
 }
 
-/*!
-    Function that takes a parameter \a v.
-    Also returns the value of \a v.
-\if defined(test_ignoresince)
-    \since Test 1.0
-\endif
-*/
+// Documented below with an \fn command. Unnecessary but we support it, and it's used.
 int Test::someFunction(int v)
 {
     return v;
@@ -143,6 +137,16 @@ int Test::someFunction(int v)
 */
 
 /*!
+    \fn int Test::someFunction(int v = 0)
+
+    Function that takes a parameter \a v.
+    Also returns the value of \a v.
+\if defined(test_ignoresince)
+    \since Test 1.0
+\endif
+*/
+
+/*!
     Function that must be reimplemented.
 */
 void Test::virtualFun()
diff --git a/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.h b/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.h
index 4ae33a404..cb812375b 100644
--- a/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.h
+++ b/tests/auto/qdoc/generatedoutput/testdata/testcpp/testcpp.h
@@ -41,7 +41,7 @@ public:
         OmittedValue = 99
     };
 #endif
-    int someFunction(int v);
+    int someFunction(int v = 0);
     void someFunctionDefaultArg(int i, bool b);
     void obsoleteMember();
     void anotherObsoleteMember();