1 files changed, 134 insertions, 0 deletions
diff --git a/meson/mesonbuild/cmake/generator.py b/meson/mesonbuild/cmake/generator.py
new file mode 100644
index 000000000..848fdf944
--- /dev/null
+++ b/meson/mesonbuild/cmake/generator.py
@@ -0,0 +1,134 @@
+# Copyright 2019 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.
+
+from .. import mesonlib
+import typing as T
+
+def parse_generator_expressions(raw: str) -> str:
+    '''Parse CMake generator expressions
+
+    Most generator expressions are simply ignored for
+    simplicety, however some are required for some common
+    use cases.
+    '''
+
+    # Early abort if no generator expression present
+    if '$<' not in raw:
+        return raw
+
+    out = ''  # type: str
+    i = 0     # type: int
+
+    def equal(arg: str) -> str:
+        col_pos = arg.find(',')
+        if col_pos < 0:
+            return '0'
+        else:
+            return '1' if arg[:col_pos] == arg[col_pos + 1:] else '0'
+
+    def vers_comp(op: str, arg: str) -> str:
+        col_pos = arg.find(',')
+        if col_pos < 0:
+            return '0'
+        else:
+            return '1' if mesonlib.version_compare(arg[:col_pos], '{}{}'.format(op, arg[col_pos + 1:])) else '0'
+
+    supported = {
+        # Boolean functions
+        'BOOL': lambda x: '0' if x.upper() in ['0', 'FALSE', 'OFF', 'N', 'NO', 'IGNORE', 'NOTFOUND'] or x.endswith('-NOTFOUND') else '1',
+        'AND': lambda x: '1' if all([y == '1' for y in x.split(',')]) else '0',
+        'OR': lambda x: '1' if any([y == '1' for y in x.split(',')]) else '0',
+        'NOT': lambda x: '0' if x == '1' else '1',
+
+        '0': lambda x: '',
+        '1': lambda x: x,
+
+        # String operations
+        'STREQUAL': equal,
+        'EQUAL': equal,
+        'VERSION_LESS': lambda x: vers_comp('<', x),
+        'VERSION_GREATER': lambda x: vers_comp('>', x),
+        'VERSION_EQUAL': lambda x: vers_comp('=', x),
+        'VERSION_LESS_EQUAL': lambda x: vers_comp('<=', x),
+        'VERSION_GREATER_EQUAL': lambda x: vers_comp('>=', x),
+
+        # String modification
+        'LOWER_CASE': lambda x: x.lower(),
+        'UPPER_CASE': lambda x: x.upper(),
+
+        # Always assume the BUILD_INTERFACE is valid.
+        # INSTALL_INTERFACE is always invalid for subprojects and
+        # it should also never appear in CMake config files, used
+        # for dependencies
+        'INSTALL_INTERFACE': lambda x: '',
+        'BUILD_INTERFACE': lambda x: x,
+
+        # Constants
+        'ANGLE-R': lambda x: '>',
+        'COMMA': lambda x: ',',
+        'SEMICOLON': lambda x: ';',
+    }  # type: T.Dict[str, T.Callable[[str], str]]
+
+    # Recursively evaluate generator expressions
+    def eval_generator_expressions() -> str:
+        nonlocal i
+        i += 2
+
+        func = ''  # type: str
+        args = ''  # type: str
+        res = ''   # type: str
+        exp = ''   # type: str
+
+        # Determine the body of the expression
+        while i < len(raw):
+            if raw[i] == '>':
+                # End of the generator expression
+                break
+            elif i < len(raw) - 1 and raw[i] == '$' and raw[i + 1] == '<':
+                # Nested generator expression
+                exp += eval_generator_expressions()
+            else:
+                # Generator expression body
+                exp += raw[i]
+
+            i += 1
+
+        # Split the expression into a function and arguments part
+        col_pos = exp.find(':')
+        if col_pos < 0:
+            func = exp
+        else:
+            func = exp[:col_pos]
+            args = exp[col_pos + 1:]
+
+        func = func.strip()
+        args = args.strip()
+
+        # Evaluate the function
+        if func in supported:
+            res = supported[func](args)
+
+        return res
+
+    while i < len(raw):
+        if i < len(raw) - 1 and raw[i] == '$' and raw[i + 1] == '<':
+            # Generator expression detected --> try resolving it
+            out += eval_generator_expressions()
+        else:
+            # Normal string, leave unchanged
+            out += raw[i]
+
+        i += 1
+
+    return out