cmake: resolve symlinks when comparing source directories.

Testcase: trying to use an existing build dir which was
made for /d/foo where /d is a symlink to $HOME/d.

To help understanding the problem, the error message now prints
both source dirs, the one found in the builddir and the one we expected.

Change-Id: I9a24fbd6ef3cf8108c5edba0d2a5b99ecdea0e89
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/libs/utils/fileutils.cpp

@@ -207,9 +207,8 @@ bool FileUtils::isFileNewerThan(const FileName &filePath, const QDateTime &timeS
 }
 
 /*!
-  Recursively resolves possibly present symlinks in \a filePath.
-  Unlike QFileInfo::canonicalFilePath(), this function will still return the expected target file
-  even if the symlink is dangling.
+  Recursively resolves symlinks if \a filePath is a symlink.
+  To resolve symlinks anywhere in the path, see canonicalPath
 
   \note Maximum recursion depth == 16.
 
@@ -226,6 +225,21 @@ FileName FileUtils::resolveSymlinks(const FileName &path)
     return FileName::fromString(f.filePath());
 }
 
+/*!
+  Recursively resolves possibly present symlinks in \a filePath.
+  Unlike QFileInfo::canonicalFilePath(), this function will not return an empty
+  string if path doesn't exist.
+
+  Returns the canonical path.
+*/
+FileName FileUtils::canonicalPath(const FileName &path)
+{
+    const QString result = QFileInfo(path.toString()).canonicalFilePath();
+    if (result.isEmpty())
+        return path;
+    return FileName::fromString(result);
+}
+
 /*!
   Like QDir::toNativeSeparators(), but use prefix '~' instead of $HOME on unix systems when an
   absolute path is given.

src/libs/utils/fileutils.h

@@ -109,6 +109,7 @@ public:
                                 QString *error = 0, const std::function<bool (QFileInfo, QFileInfo, QString *)> &copyHelper = std::function<bool (QFileInfo, QFileInfo, QString *)>());
     static bool isFileNewerThan(const FileName &filePath, const QDateTime &timeStamp);
     static FileName resolveSymlinks(const FileName &path);
+    static FileName canonicalPath(const FileName &path);
     static QString shortNativePath(const FileName &path);
     static QString fileSystemFriendlyName(const QString &name);
     static int indexOfQmakeUnfriendly(const QString &name, int startpos = 0);

src/plugins/cmakeprojectmanager/builddirmanager.cpp

@@ -286,8 +286,12 @@ CMakeConfig BuildDirManager::parsedConfiguration() const
             emit errorOccured(errorMessage);
         const Utils::FileName sourceOfBuildDir
                 = Utils::FileName::fromUtf8(CMakeConfigItem::valueOf("CMAKE_HOME_DIRECTORY", m_cmakeCache));
-        if (sourceOfBuildDir != sourceDirectory()) // Use case-insensitive compare where appropriate
-            emit errorOccured(tr("The build directory is not for %1").arg(sourceDirectory().toUserOutput()));
+        const Utils::FileName canonicalSourceOfBuildDir = Utils::FileUtils::canonicalPath(sourceOfBuildDir);
+        const Utils::FileName canonicalSourceDirectory = Utils::FileUtils::canonicalPath(sourceDirectory());
+        if (canonicalSourceOfBuildDir != canonicalSourceDirectory) // Uses case-insensitive compare where appropriate
+            emit errorOccured(tr("The build directory is not for %1 but for %2")
+                    .arg(canonicalSourceOfBuildDir.toUserOutput(),
+                         canonicalSourceDirectory.toUserOutput()));
     }
     return m_cmakeCache;
 }