Conan: Add optional ICU Conan package dependency

If the "icu" option is passed for the build then add the optional
ICU Conan package dependency. The ICU version needs to be parsed
from a file which is provisioned by the Qt CI.

If the ICU version can not be parsed, e.g. if "conan export" is
being executed outside Qt CI machines, then use a fallback
version for it.

For the Qt build system to pick up the ICU dependency built
by Conan we need to pass the ICU package path via
CMAKE_PREFIX_PATH.

Task-number: QTBUG-97072
Change-Id: I83059664c59dff68af76da8509e618442b530516
Reviewed-by: Toni Saario <toni.saario@qt.io>
(cherry picked from commit f2230ea1a6c83bade142eca0a696dc1e219d427f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

conanfile.py

@@ -31,6 +31,7 @@ from conans.errors import ConanInvalidConfiguration
 import os
 import re
 import json
+import shutil
 import subprocess
 from functools import lru_cache
 from pathlib import Path
@@ -328,11 +329,28 @@ class QtOptionParser:
         return ret
 
 
+def add_cmake_prefix_path(conan_file: ConanFile, dep: str) -> None:
+    if dep not in conan_file.deps_cpp_info.deps:
+        raise QtConanError("Unable to find dependency: {0}".format(dep))
+    dep_cpp_info = conan_file.deps_cpp_info[dep]
+    cmake_args_str = str(conan_file.options.get_safe("cmake_args_qtbase", default=""))
+    _common = conan_file.python_requires["qt-conan-common"].module
+    formatted_cmake_args_str = _common.append_cmake_prefix_path(
+        cmake_args_str, dep_cpp_info.rootpath
+    )
+    print("Adjusted cmake args for qtbase build: {0}".format(formatted_cmake_args_str))
+    setattr(conan_file.options, "cmake_args_qtbase", formatted_cmake_args_str)
+
+
 def _build_qtbase(conan_file: ConanFile):
     # we call the Qt's configure(.bat) directly
     script = Path("configure.bat") if tools.os_info.is_windows else Path("configure")
     configure = Path(conan_file.build_folder).joinpath(script).resolve(strict=True)
 
+    if conan_file.options.get_safe("icu", default="no"):
+        # we need to tell Qt build system where to find the ICU
+        add_cmake_prefix_path(conan_file, dep="icu")
+
     # convert the Conan options to Qt configure(.bat) arguments
     parser = conan_file._qt_option_parser
     qt_configure_options = parser.convert_conan_options_to_qt_options(conan_file.options)
@@ -372,7 +390,6 @@ class QtBase(ConanFile):
     _qt_option_parser = QtOptionParser()
     options = _qt_option_parser.get_qt_conan_options()
     default_options = _qt_option_parser.get_default_qt_conan_options()
-    exports = "configure_options.json", "configure_features.txt", ".cmake.conf"
     exports_sources = "*", "!conan*.*"
     # use commit ID as the RREV (recipe revision)
     revision_mode = "scm"
@@ -385,6 +402,42 @@ class QtBase(ConanFile):
         _prerelease = _parse_qt_version_by_key("QT_REPO_MODULE_PRERELEASE_VERSION_SEGMENT")
         self.version = _ver + "-" + _prerelease if _prerelease else _ver
 
+    def export(self):
+        self.copy("configure_options.json")
+        self.copy("configure_features.txt")
+        self.copy(".cmake.conf")
+        _common = self.python_requires["qt-conan-common"].module
+        conf = _common.qt_sw_versions_config_folder() / _common.qt_sw_versions_config_name()
+        if not conf.exists():
+            # If using "conan export" outside Qt CI provisioned machines
+            print("Warning: Couldn't find '{0}'. 3rd party dependencies skipped.".format(conf))
+        else:
+            shutil.copy2(conf, self.export_folder)
+
+    def requirements(self):
+        parse_sw_req = self.python_requires["qt-conan-common"].module.parse_qt_sw_pkg_dependency
+        # list of tuples, (package_name, fallback version)
+        optional_requirements = [("icu", "56.1")]
+        for req_name, req_ver_fallback in optional_requirements:
+            if self.options.get_safe(req_name, default="no") == "yes":
+                # Note! If this conan package is being "conan export"ed outside Qt CI and the
+                # sw versions .ini file is not present then it will fall-back to default version
+                ver = parse_sw_req(
+                    config_folder=Path(self.recipe_folder),
+                    package_name=req_name,
+                    target_os=str(self.settings.os),
+                )
+                if not ver:
+                    print(
+                        "Warning: Using fallback version '{0}' for: {1}".format(
+                            req_name, req_ver_fallback
+                        )
+                    )
+                    ver = req_ver_fallback
+                requirement = "{0}/{1}@qt/everywhere".format(req_name, ver)
+                print("Setting 3rd party package requirement: {0}".format(requirement))
+                self.requires(requirement)
+
     def configure(self):
         if self.settings.compiler == "gcc" and tools.Version(self.settings.compiler.version) < "8":
             raise ConanInvalidConfiguration("Qt6 does not support GCC before 8")