qmake: let QMakeVfs::readFile() report ENOFILE explicitly

when the QFile object is already constructed, querying whether the file
exists is actually cheap, so do it right away instead of later on
demand. that makes the calling code a bit cleaner.

fwiw, that we need to explicitly query the file's existence at all is a
result of QFile's completely useless error "codes" (which merely say
which function failed, as if the caller would not know).

Change-Id: Ifec39d05b1713d8128046f679287e510f10e45dc
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
(cherry picked from qtcreator/5ba32e3484ead2e35cc7732dcd59a97e7459dbfd)
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

1 files changed, 7 insertions, 1 deletions

diff --git a/qmake/library/qmakevfs.h b/qmake/library/qmakevfs.h
index 8677ba08c1..5e6a2f88e2 100644
--- a/qmake/library/qmakevfs.h
+++ b/qmake/library/qmakevfs.h
@@ -45,10 +45,16 @@ QT_BEGIN_NAMESPACE
 class QMAKE_EXPORT QMakeVfs
 {
 public:
+    enum ReadResult {
+        ReadOk,
+        ReadNotFound,
+        ReadOtherError
+    };
+
     QMakeVfs();
 
     bool writeFile(const QString &fn, QIODevice::OpenMode mode, bool exe, const QString &contents, QString *errStr);
-    bool readFile(const QString &fn, QString *contents, QString *errStr);
+    ReadResult readFile(const QString &fn, QString *contents, QString *errStr);
     bool exists(const QString &fn);
 
 #ifndef PROEVALUATOR_FULL