add support for generating cmake files

This new cmake module allows to generate cmake package files. This may ease the
porting for cmake projects that are exporting cmake package informations for other
depending projects. The module uses as much as possible the templates provided by
the cmake installation (and so cmake needs to be installed).

docs/markdown/CMake-module.md

@@ -0,0 +1,71 @@
+# CMake module
+
+This module provides helper tools for generating cmake package files.
+
+
+## Usage
+
+To use this module, just do: **`cmake = import('cmake')`**. The
+following functions will then be available as methods on the object
+with the name `cmake`. You can, of course, replace the name `cmake`
+with anything else.
+
+### cmake.write_basic_package_version_file()
+
+This function is the equivalent of the corresponding [CMake function](https://cmake.org/cmake/help/v3.11/module/CMakePackageConfigHelpers.html#generating-a-package-version-file),
+it generates a `name` package version file.
+
+* `name`: the name of the package.
+* `version`: the version of the generated package file.
+* `compatibility`: a string indicating the kind of compatibility, the accepted values are
+`AnyNewerVersion`, `SameMajorVersion`, `SameMinorVersion` or `ExactVersion`.
+It defaults to `AnyNewerVersion`. Depending on your cmake installation some kind of
+compatibility may not be available.
+* `install_dir`: optional installation directory, it defaults to `$(libdir)/cmake/$(name)`
+
+
+Example:
+
+```meson
+cmake = import('cmake')
+
+cmake.write_basic_package_version_file(name: 'myProject', version: '1.0.0')
+```
+
+### cmake.configure_package_config_file()
+
+This function is the equivalent of the corresponding [CMake function](https://cmake.org/cmake/help/v3.11/module/CMakePackageConfigHelpers.html#generating-a-package-configuration-file),
+it generates a `name` package configuration file from the `input` template file. Just like the cmake function
+in this file the `@PACKAGE_INIT@` statement will be replaced by the appropriate piece of cmake code.
+The equivalent `PATH_VARS` argument is given through the `configuration` parameter.
+
+* `name`: the name of the package.
+* `input`: the template file where that will be treated for variable substitutions contained in `configuration`.
+* `install_dir`: optional installation directory, it defaults to `$(libdir)/cmake/$(name)`.
+* `configuration`: a `configuration_data` object that will be used for variable substitution in the template file.
+
+
+Example:
+
+meson.build:
+
+```meson
+cmake = import('cmake')
+
+conf = configuration_data()
+conf.set_quoted('VAR', 'variable value')
+
+cmake.configure_package_config_file(
+    name: 'myProject',
+    input: 'myProject.cmake.in',
+    configuration: conf
+)
+```
+
+myProject.cmake.in:
+
+```text
+@PACKAGE_INIT@
+
+set(MYVAR VAR)
+```

docs/markdown/Module-reference.md

@@ -2,6 +2,7 @@ Meson has a selection of modules to make common requirements easy to use.
 Modules can be thought of like the standard library of a programming language.
 Currently Meson provides the following modules.
 
+* [CMake](CMake-module.md)
 * [Gnome](Gnome-module.md)
 * [i18n](i18n-module.md)
 * [Qt4](Qt4-module.md)

mesonbuild/modules/cmake.py

@@ -0,0 +1,217 @@
+# Copyright 2018 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import re
+import os, os.path
+import shutil
+
+from . import ExtensionModule, permittedSnippetKwargs, ModuleReturnValue
+
+from .. import build, dependencies, mesonlib, mlog
+from ..interpreterbase import permittedKwargs
+from ..interpreter import ConfigurationDataHolder
+
+
+COMPATIBILITIES = ['AnyNewerVersion', 'SameMajorVersion', 'SameMinorVersion', 'ExactVersion']
+
+# Taken from https://github.com/Kitware/CMake/blob/master/Modules/CMakePackageConfigHelpers.cmake
+PACKAGE_INIT_BASE = '''
+####### Expanded from @PACKAGE_INIT@ by configure_package_config_file() #######
+####### Any changes to this file will be overwritten by the next CMake run ####
+####### The input file was @inputFileName@                             ########
+get_filename_component(PACKAGE_PREFIX_DIR "${CMAKE_CURRENT_LIST_DIR}/@PACKAGE_RELATIVE_PATH@" ABSOLUTE)
+'''
+PACKAGE_INIT_EXT = '''
+# Use original install prefix when loaded through a "/usr move"
+# cross-prefix symbolic link such as /lib -> /usr/lib.
+get_filename_component(_realCurr "${CMAKE_CURRENT_LIST_DIR}" REALPATH)
+get_filename_component(_realOrig "@absInstallDir@" REALPATH)
+if(_realCurr STREQUAL _realOrig)
+  set(PACKAGE_PREFIX_DIR "@installPrefix@")
+endif()
+unset(_realOrig)
+unset(_realCurr)
+'''
+
+
+class CmakeModule(ExtensionModule):
+    cmake_detected = False
+    cmake_root = None
+
+    def __init__(self):
+        super().__init__()
+        self.snippets.add('configure_package_config_file')
+
+    def detect_voidp_size(self, compilers, env):
+        compiler = compilers.get('c', None)
+        if not compiler:
+            compiler = compilers.get('cpp', None)
+
+        if not compiler:
+            raise mesonlib.MesonException('Requires a C or C++ compiler to compute sizeof(void *).')
+
+        return compiler.sizeof('void *', '', env)
+
+    def detect_cmake(self):
+        if self.cmake_detected:
+            return True
+
+        cmakebin = dependencies.ExternalProgram('cmake', silent=False)
+        p, stdout, _stderr = mesonlib.Popen_safe(cmakebin.get_command() + ['--system-information'])[0:3]
+        if p.returncode != 0:
+            mlog.log('cmake not found, returnCode={}'.format(p.returncode))
+            return False
+
+        match = re.search('\n_INCLUDED_FILE \\"([^"]+)"\n', stdout.strip())
+        if not match:
+            mlog.log('unable to determine cmake root')
+            return False
+
+        # compilerpath is something like '/usr/share/cmake-3.5/Modules/Platform/Linux-GNU-CXX.cmake'
+        compilerpath = match.group(1)
+        pos = compilerpath.find(os.path.sep + os.path.join("Modules", "Platform", ""))
+        if pos < 0:
+            mlog.log('unknown _INCLUDED_FILE path scheme')
+            return False
+
+        self.cmake_root = compilerpath[0:pos]
+        self.cmake_detected = True
+        return True
+
+    @permittedKwargs({'version', 'name', 'compatibility', 'install_dir'})
+    def write_basic_package_version_file(self, state, _args, kwargs):
+        version = kwargs.get('version', None)
+        if not isinstance(version, str):
+            raise mesonlib.MesonException('Version must be specified.')
+
+        name = kwargs.get('name', None)
+        if not isinstance(name, str):
+            raise mesonlib.MesonException('Name not specified.')
+
+        compatibility = kwargs.get('compatibility', 'AnyNewerVersion')
+        if not isinstance(compatibility, str):
+            raise mesonlib.MesonException('compatibility is not string.')
+        if compatibility not in COMPATIBILITIES:
+            raise mesonlib.MesonException('compatibility must be either AnyNewerVersion, SameMajorVersion or ExactVersion.')
+
+        if not self.detect_cmake():
+            raise mesonlib.MesonException('Unable to find cmake')
+
+        pkgroot = kwargs.get('install_dir', None)
+        if pkgroot is None:
+            pkgroot = os.path.join(state.environment.coredata.get_builtin_option('libdir'), 'cmake', name)
+        if not isinstance(pkgroot, str):
+            raise mesonlib.MesonException('Install_dir must be a string.')
+
+        template_file = os.path.join(self.cmake_root, 'Modules', 'BasicConfigVersion-{}.cmake.in'.format(compatibility))
+        if not os.path.exists(template_file):
+            raise mesonlib.MesonException('your cmake installation doesn\'t support the {} compatibility'.format(compatibility))
+
+        version_file = os.path.join(state.environment.scratch_dir, '{}ConfigVersion.cmake'.format(name))
+
+        conf = {
+            'CVF_VERSION': (version, ''),
+            'CMAKE_SIZEOF_VOID_P': (str(self.detect_voidp_size(state.compilers, state.environment)), '')
+        }
+        mesonlib.do_conf_file(template_file, version_file, conf)
+
+        res = build.Data(mesonlib.File(True, state.environment.get_scratch_dir(), version_file), pkgroot)
+        return ModuleReturnValue(res, [res])
+
+    def create_package_file(self, infile, outfile, PACKAGE_RELATIVE_PATH, extra, confdata):
+        package_init = PACKAGE_INIT_BASE.replace('@PACKAGE_RELATIVE_PATH@', PACKAGE_RELATIVE_PATH)
+        package_init += extra
+
+        try:
+            with open(infile, "r") as fin:
+                data = fin.readlines()
+        except Exception as e:
+            raise mesonlib.MesonException('Could not read input file %s: %s' % (infile, str(e)))
+
+        result = []
+        regex = re.compile(r'(?:\\\\)+(?=\\?@)|\\@|@([-a-zA-Z0-9_]+)@')
+        for line in data:
+            line = line.replace('@PACKAGE_INIT@', package_init)
+            line, _missing = mesonlib.do_replacement(regex, line, confdata)
+
+            result.append(line)
+
+        outfile_tmp = outfile + "~"
+        with open(outfile_tmp, "w", encoding='utf-8') as fout:
+            fout.writelines(result)
+
+        shutil.copymode(infile, outfile_tmp)
+        mesonlib.replace_if_different(outfile, outfile_tmp)
+
+    @permittedSnippetKwargs({'input', 'name', 'install_dir', 'configuration'})
+    def configure_package_config_file(self, interpreter, state, args, kwargs):
+        if len(args) > 0:
+            raise mesonlib.MesonException('configure_package_config_file takes only keyword arguments.')
+
+        if 'input' not in kwargs:
+            raise mesonlib.MesonException('configure_package_config_file requires "input" keyword.')
+        inputfile = kwargs['input']
+        if isinstance(inputfile, list):
+            if len(inputfile) != 1:
+                m = "Keyword argument 'input' requires exactly one file"
+                raise mesonlib.MesonException(m)
+            inputfile = inputfile[0]
+        if not isinstance(inputfile, (str, mesonlib.File)):
+            raise mesonlib.MesonException("input must be a string or a file")
+        if isinstance(inputfile, str):
+            inputfile = mesonlib.File.from_source_file(state.environment.source_dir, state.subdir, inputfile)
+
+        ifile_abs = inputfile.absolute_path(state.environment.source_dir, state.environment.build_dir)
+
+        if 'name' not in kwargs:
+            raise mesonlib.MesonException('"name" not specified.')
+        name = kwargs['name']
+
+        (ofile_path, ofile_fname) = os.path.split(os.path.join(state.subdir, '{}Config.cmake'.format(name)))
+        ofile_abs = os.path.join(state.environment.build_dir, ofile_path, ofile_fname)
+
+        if 'install_dir' not in kwargs:
+            install_dir = os.path.join(state.environment.coredata.get_builtin_option('libdir'), 'cmake', name)
+        if not isinstance(install_dir, str):
+            raise mesonlib.MesonException('"install_dir" must be a string.')
+
+        if 'configuration' not in kwargs:
+            raise mesonlib.MesonException('"configuration" not specified.')
+        conf = kwargs['configuration']
+        if not isinstance(conf, ConfigurationDataHolder):
+            raise mesonlib.MesonException('Argument "configuration" is not of type configuration_data')
+
+        prefix = state.environment.coredata.get_builtin_option('prefix')
+        abs_install_dir = install_dir
+        if not os.path.isabs(abs_install_dir):
+            abs_install_dir = os.path.join(prefix, install_dir)
+
+        PACKAGE_RELATIVE_PATH = os.path.relpath(prefix, abs_install_dir)
+        extra = ''
+        if re.match('^(/usr)?/lib(64)?/.+', abs_install_dir):
+            extra = PACKAGE_INIT_EXT.replace('@absInstallDir@', abs_install_dir)
+            extra = extra.replace('@installPrefix@', prefix)
+
+        self.create_package_file(ifile_abs, ofile_abs, PACKAGE_RELATIVE_PATH, extra, conf.held_object)
+
+        conffile = os.path.normpath(inputfile.relative_name())
+        if conffile not in interpreter.build_def_files:
+            interpreter.build_def_files.append(conffile)
+
+        res = build.Data(mesonlib.File(True, ofile_path, ofile_fname), install_dir)
+        interpreter.build.data.append(res)
+
+        return res
+
+def initialize():
+    return CmakeModule()

test cases/common/178 cmake module/meson.build

@@ -0,0 +1,17 @@
+project('cmakeModule', 'c')
+
+cmake = import('cmake')
+
+cmake.write_basic_package_version_file(version: '0.0.1',
+	name: 'cmakeModule',
+)
+
+conf = configuration_data()
+conf.set('MYVAR', 'my variable value')
+conf.set_quoted('MYQUOTEDVAR', 'my quoted variable value')
+
+cmake.configure_package_config_file(
+    input: 'projectConfig.cmake.in',
+    name: 'cmakeModule',
+    configuration: conf,
+)

test cases/common/178 cmake module/projectConfig.cmake.in

@@ -0,0 +1,4 @@
+@PACKAGE_INIT@
+
+set(MYVAR "@MYVAR@")
+set(MYQUOTEDVAR @MYQUOTEDVAR@)