QtSupport: Detect all Qt versions in PATH

There is no reason to limit the number of auto-detected Qt versions to
one, in particular when there's systems (e.g. ArchLinux) where the
plain, version-less qmake executable points to Qt 5 and Qt 6 therefore
did not get auto-detected at all.

Change-Id: I288a964c23ef4319fcfcc31d098c0f385614d369
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/buildablehelperlibrary.cpp

@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
 
 #include "buildablehelperlibrary.h"
+
+#include "algorithm.h"
 #include "environment.h"
 #include "hostosinfo.h"
 #include "qtcprocess.h"
@@ -42,7 +44,7 @@ FilePath BuildableHelperLibrary::qtChooserToQmakePath(const FilePath &qtChooser)
 
 static bool isQmake(FilePath path)
 {
-    if (path.isEmpty())
+    if (!path.isExecutableFile())
         return false;
     if (BuildableHelperLibrary::isQtChooser(path))
         path = BuildableHelperLibrary::qtChooserToQmakePath(path.symLinkTarget());
@@ -51,37 +53,42 @@ static bool isQmake(FilePath path)
     return !BuildableHelperLibrary::qtVersionForQMake(path).isEmpty();
 }
 
-static FilePath findQmakeInDir(const FilePath &dir)
+static FilePaths findQmakesInDir(const FilePath &dir)
 {
     if (dir.isEmpty())
         return {};
 
-    FilePath qmakePath = dir.pathAppended("qmake").withExecutableSuffix();
-    if (qmakePath.exists()) {
-        if (isQmake(qmakePath))
-            return qmakePath;
-    }
-
     // Prefer qmake-qt5 to qmake-qt4 by sorting the filenames in reverse order.
+    FilePaths qmakes;
+    std::set<FilePath> canonicalQmakes;
     const FilePaths candidates = dir.dirEntries(
                 {BuildableHelperLibrary::possibleQMakeCommands(), QDir::Files},
                 QDir::Name | QDir::Reversed);
+
+    const auto probablyMatchesExistingQmake = [&](const FilePath &qmake) {
+        // This deals with symlinks.
+        if (!canonicalQmakes.insert(qmake).second)
+            return true;
+
+        // Symlinks have high potential for false positives in file size check, so skip that one.
+        if (qmake.isSymLink())
+            return false;
+
+        // This deals with the case where copies are shipped instead of symlinks
+        // (Windows, Qt installer, ...).
+        return contains(qmakes, [size = qmake.fileSize()](const FilePath &existing) {
+            return existing.fileSize() == size;
+        });
+    };
+
     for (const FilePath &candidate : candidates) {
-        if (candidate == qmakePath)
-            continue;
-        if (isQmake(candidate))
-            return candidate;
+        if (isQmake(candidate) && !probablyMatchesExistingQmake(candidate))
+            qmakes << candidate;
     }
-    return {};
+    return qmakes;
 }
 
-FilePath BuildableHelperLibrary::findSystemQt(const Environment &env)
-{
-    const FilePaths list = findQtsInEnvironment(env, 1);
-    return list.size() == 1 ? list.first() : FilePath();
-}
-
-FilePaths BuildableHelperLibrary::findQtsInEnvironment(const Environment &env, int maxCount)
+FilePaths BuildableHelperLibrary::findQtsInEnvironment(const Environment &env)
 {
     FilePaths qmakeList;
     std::set<FilePath> canonicalEnvPaths;
@@ -89,12 +96,7 @@ FilePaths BuildableHelperLibrary::findQtsInEnvironment(const Environment &env, i
     for (const FilePath &path : paths) {
         if (!canonicalEnvPaths.insert(path.canonicalPath()).second)
             continue;
-        const FilePath qmake = findQmakeInDir(path);
-        if (qmake.isEmpty())
-            continue;
-        qmakeList << qmake;
-        if (maxCount != -1 && qmakeList.size() == maxCount)
-            break;
+        qmakeList << findQmakesInDir(path);
     }
     return qmakeList;
 }

src/libs/utils/buildablehelperlibrary.h

@@ -16,10 +16,7 @@ class Environment;
 class QTCREATOR_UTILS_EXPORT BuildableHelperLibrary
 {
 public:
-    // returns the full path to the first qmake, qmake-qt4, qmake4 that has
-    // at least version 2.0.0 and thus is a qt4 qmake
-    static FilePath findSystemQt(const Environment &env);
-    static FilePaths findQtsInEnvironment(const Environment &env, int maxCount = -1);
+    static FilePaths findQtsInEnvironment(const Environment &env);
     static bool isQtChooser(const FilePath &filePath);
     static FilePath qtChooserToQmakePath(const FilePath &path);
     // return true if the qmake at qmakePath is a Qt (used by QtVersion)