configure: CMake: Add -no-prefix option

Introduce a new -no-prefix option that can be used to build Qt without
having to install it.

Currently, -no-prefix is already implied by -developer-build, but
-developer-build also implies -warnings-are-errors and
-feature-private-tests, which not everyone might want to use.

Some Qt builders likely use -developer-build for the no-prefix
behavior, hence we introduce a standalone -no-prefix option to offer
a nicer user experience without -Werror and friends.

Previously it was possible to achieve the same by specifying
-prefix $PWD, but that relies on $PWD expanding property in the used
shell.

The new -no-prefix doesn't depend on the type of the shell and
is shorter to type.

Internally this gets passed by configure as -DINPUT_no_prefix=yes to
CMake, and transformed into a -DQT_FEATURE_no_prefix=ON feature.

The feature also gets automatically auto-detected to ON if
developer-build is set, -prefix is either unset or $PWD.

CMake code should still query QT_WILL_INSTALL to decide whether
files need to be installed or not.

As a drive-by, we now also export QT_FEATURE_developer_build to
be available for querying during configuration of other repos
(previously it was only possible to query FEATURE_developer_build).

Change-Id: Iaa6c8d8ae2b736282e9949d2a5d7f412e290a253
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
(cherry picked from commit 32b596b7b10eac63293cf3bd3e04a15bd826fbf1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

cmake/QtProcessConfigureArgs.cmake

@@ -600,6 +600,10 @@ while(1)
     if(arg MATCHES "^--?enable-(.*)")
         set(opt "${CMAKE_MATCH_1}")
         set(val "yes")
+    # Handle -no-prefix so it's not interpreted as the negation of -prefix
+    elseif(arg MATCHES "-(no-prefix)")
+        set(opt "${CMAKE_MATCH_1}")
+        set(val "")
     elseif(arg MATCHES "^--?(disable|no)-(.*)")
         set(opt "${CMAKE_MATCH_2}")
         set(val "no")
@@ -902,6 +906,10 @@ foreach(input ${config_inputs})
     push("-DINPUT_${cmake_input}=${INPUT_${input}}")
 endforeach()
 
+if(DEFINED INPUT_no-prefix AND DEFINED INPUT_prefix)
+    qtConfAddError("Can't specify both -prefix and -no-prefix options at the same time.")
+endif()
+
 if(NOT generator AND auto_detect_generator)
     find_program(ninja ninja)
     if(ninja)

cmake/QtSetup.cmake

@@ -11,6 +11,13 @@ if(NOT FEATURE_developer_build AND INPUT_developer_build
     set(FEATURE_developer_build ON)
 endif()
 
+# Pre-calculate the no_prefix feature if it's set by configure via INPUT_no_prefix.
+# This needs to be done before qtbase/configure.cmake is processed.
+if(NOT FEATURE_no_prefix AND INPUT_no_prefix
+        AND NOT "${INPUT_no_prefix}" STREQUAL "undefined")
+    set(FEATURE_no_prefix ON)
+endif()
+
 set(_default_build_type "Release")
 if(FEATURE_developer_build)
     set(_default_build_type "Debug")
@@ -95,7 +102,11 @@ set(CMAKE_LINK_DEPENDS_NO_SHARED ON)
 # QtBuildInternalsExtra.cmake file.
 if (PROJECT_NAME STREQUAL "QtBase" AND NOT QT_BUILD_STANDALONE_TESTS)
     if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
-        if(FEATURE_developer_build)
+        # Handle both FEATURE_ and QT_FEATURE_ cases when they are specified on the command line
+        # explicitly. It's possible for one to be set, but not the other, because
+        # qtbase/configure.cmake is not processed by this point.
+        if(FEATURE_developer_build OR QT_FEATURE_developer_build
+            OR FEATURE_no_prefix OR QT_FEATURE_no_prefix)
             # Handle non-prefix builds by setting the CMake install prefix to point to qtbase's
             # build dir. While building another repo (like qtsvg) the CMAKE_PREFIX_PATH should be
             # set on the command line to point to the qtbase build dir.

cmake/configure-cmake-mapping.md

@@ -3,6 +3,8 @@ The following table describes the mapping of configure options to CMake argument
 | configure                             | cmake                                             | Notes                                                           |
 |---------------------------------------|---------------------------------------------------|-----------------------------------------------------------------|
 | -prefix /opt/qt6                      | -DCMAKE_INSTALL_PREFIX=/opt/qta6                  |                                                                 |
+| -no-prefix (only available in Qt6)    | -DCMAKE_INSTALL_PREFIX=$PWD (with bash)           | In Qt5 this was done by specifying -prefix $PWD                 |
+|                                         or -DFEATURE_no_prefix=ON                         |                                                                 |
 | -extprefix /opt/qt6                   | -DCMAKE_STAGING_PREFIX=/opt/qt6                   |                                                                 |
 | -bindir <dir>                         | -DINSTALL_BINDIR=<dir>                            | similar for -headerdir -libdir and so on                        |
 | -hostdatadir <dir>                    | -DINSTALL_MKSPECSDIR=<dir>                        |                                                                 |

config_help.txt

@@ -7,6 +7,10 @@ Top-level installation directories:
   -prefix <dir> ...... The deployment directory, as seen on the target device.
                        [/usr/local/Qt-$QT_VERSION; qtbase build directory if
                        -developer-build]
+  -no-prefix ......... The deployment directory is set to the qtbase build
+                       directory. Can be used instead of -developer-build
+                       to not have to install, as well as avoid
+                       -developer-build's default of -warnings-are-errors.
   -extprefix <dir> ... The installation directory, as seen on the host machine.
                        [SYSROOT/PREFIX]
 

configure.cmake

@@ -467,10 +467,18 @@ qt_feature("pkg-config" PUBLIC
 )
 qt_feature_config("pkg-config" QMAKE_PUBLIC_QT_CONFIG
     NEGATE)
-qt_feature("developer-build"
+qt_feature("developer-build" PRIVATE
     LABEL "Developer build"
     AUTODETECT OFF
 )
+qt_feature("no-prefix" PRIVATE
+    LABEL "No prefix build"
+    # The var expansion on the right hand side is on purpose
+    # because the custom condition evaluator only expands the lhs
+    CONDITION (CMAKE_INSTALL_PREFIX STREQUAL "${QtBase_BINARY_DIR}")
+              OR CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT
+    AUTODETECT QT_FEATURE_developer_build
+)
 qt_feature("private_tests" PRIVATE
     LABEL "Developer build: private_tests"
     CONDITION QT_FEATURE_developer_build

qt_cmdline.cmake

@@ -8,6 +8,8 @@ qt_commandline_subconfig(src/printsupport)
 qt_commandline_subconfig(src/plugins/sqldrivers)
 qt_commandline_subconfig(src/testlib)
 qt_commandline_subconfig(src/tools)
+# no-prefix needs to be placed before prefix
+qt_commandline_option(no-prefix TYPE void)
 qt_commandline_option(prefix TYPE string)
 qt_commandline_option(extprefix TYPE string)
 qt_commandline_option(archdatadir TYPE string)