Improve configure2cmake to find_package only in certain conditions

It doesn't make much sense to look for X11 related packages on
macOS and Windows by default. Usually they would not be there, and
as a result the configuration step would show a long list of scary
not found packages, and also eat precious configure time.

Change the conversion script to allow putting conditions around
generated find_package calls.

These conditions can be manually set in the conversion script
library mapping, using the emit_if argument,
which we do for the X11 and Wayland related packages.

They are also computed by checking which features use a given library,
and if the feature is protected by a simple emitIf condition like
config.linux, the relevant library find_package call will be protected
by the same condition.

If a developer still wishes to look for all packages, they can define
the CACHE variable QT_FIND_ALL_PACKAGES_ALWAYS to ON.

The relevant configure.cmake files are regenerated in this patch.

Change-Id: I6f918a94f50257ec41d6216305dae9774933389a
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

1 files changed, 22 insertions, 2 deletions

diff --git a/util/cmake/configurejson2cmake.py b/util/cmake/configurejson2cmake.py
index 040e8ee7b4..d1646ed082 100755
--- a/util/cmake/configurejson2cmake.py
+++ b/util/cmake/configurejson2cmake.py
@@ -181,9 +181,29 @@ def parseLib(ctx, lib, data, cm_fh, cmake_find_packages_set):
     if newlib.targetName in cmake_find_packages_set:
         return
 
+    # If certain libraries are used within a feature, but the feature
+    # is only emitted conditionally with a simple condition (like
+    # 'on Windows' or 'on Linux'), we should enclose the find_package
+    # call for the library into the same condition.
+    emit_if = newlib.emit_if
+
+    # Only look through features if a custom emit_if wasn't provided.
+    if not emit_if:
+        for feature in data['features']:
+            feature_data = data['features'][feature]
+            if 'condition' in feature_data and \
+                    'libs.{}'.format(lib) in feature_data['condition'] and \
+                    'emitIf' in feature_data and \
+                    'config.' in feature_data['emitIf']:
+                emit_if = feature_data['emitIf']
+                break
+
+    if emit_if:
+        emit_if = map_condition(emit_if)
+
     cmake_find_packages_set.add(newlib.targetName)
 
-    cm_fh.write(generate_find_package_info(newlib))
+    cm_fh.write(generate_find_package_info(newlib, emit_if=emit_if))
 
 
 def lineify(label, value, quote=True):
@@ -890,7 +910,7 @@ def processLibraries(ctx, data, cm_fh):
         return
 
     for lib in data['libraries']:
-        parseLib(ctx, lib, data['libraries'][lib], cm_fh, cmake_find_packages_set)
+        parseLib(ctx, lib, data, cm_fh, cmake_find_packages_set)
 
 
 def processSubconfigs(dir, ctx, data):