Add parser and evaluator for rust cfg expressions

rust2rpm/cfg.py

@@ -0,0 +1,113 @@
+import ast
+import ctypes
+import functools
+import platform
+import sys
+
+import pyparsing as pp
+
+pp.ParserElement.enable_packrat()
+
+# ConfigurationPredicate :
+#      ConfigurationOption
+#    | ConfigurationAll
+#    | ConfigurationAny
+#    | ConfigurationNot
+# ConfigurationOption :
+#    IDENTIFIER (= (STRING_LITERAL | RAW_STRING_LITERAL))?
+# ConfigurationAll
+#    all ( ConfigurationPredicateList? )
+# ConfigurationAny
+#    any ( ConfigurationPredicateList? )
+# ConfigurationNot
+#    not ( ConfigurationPredicate )
+# ConfigurationPredicateList
+#    ConfigurationPredicate (, ConfigurationPredicate)* ,?
+
+# cfg(target_os = "macos")
+# cfg(any(foo, bar))
+# cfg(all(unix, target_pointer_width = "32"))
+# cfg(not(foo))
+
+def _call(word, arg):
+    return pp.Group(pp.Literal(word) + pp.Suppress('(') + arg + pp.Suppress(')'), aslist=True)
+
+@functools.cache
+def cfg_grammar():
+    pred = pp.Forward()
+
+    ident = pp.Word(pp.alphas + '_', pp.alphanums + '_')
+    option = pp.Group(ident + pp.Optional(pp.Suppress('=') + pp.quotedString), aslist=True)
+
+    not_ = _call('not', pred)
+
+    # pp.pyparsing_common.comma_separated_list?
+    # any_ = _call('any', pp.pyparsing_common.comma_separated_list(pred))
+    # all_ = _call('all', pp.pyparsing_common.comma_separated_list(pred))
+    # all_ = _call('all', pp.delimited_list(pred))
+
+    any_ = _call('any', pred + pp.ZeroOrMore(pp.Suppress(',') + pred))
+    all_ = _call('all', pred + pp.ZeroOrMore(pp.Suppress(',') + pred))
+
+    pred <<= not_ | any_ | all_ | option
+
+    grammar = _call('cfg', pred)
+    return grammar
+
+@functools.cache
+def evaluate_variable(name):
+    # print(f'evaluate_variable: {expr}')
+    match name:
+        case 'target_arch':
+            return platform.machine()
+
+        case 'target_os':
+            return 'linux'
+
+        case 'target_family':
+            return 'unix'
+
+        case 'unix':
+            return evaluate_variable('target_family') == 'unix'
+
+        case 'windows':
+            return evaluate_variable('target_family') == 'windows'
+
+        case 'target_env':
+            # Key-value option set with further disambiguating information about the
+            # target platform with information about the ABI or libc used
+            return ...
+
+        case 'target_endian':
+            return sys.byteorder
+
+        case 'target_pointer_width':
+            return str(ctypes.sizeof(ctypes.c_voidp) * 8)
+
+        case 'target_vendor':
+            return 'unknown'
+
+        case _:
+            print(f'Unknown variable {name}, assuming False')
+            return False
+
+def evaluate(expr, nested=False):
+    # print(f'evaluate: {expr}')
+    match expr:
+        case ['cfg', expr] if not nested:
+            return evaluate(expr, True)
+        case ['not', expr] if nested:
+            return not evaluate(expr, True)
+        case ['all', *args] if nested:
+            return all(evaluate(arg, True) for arg in args)
+        case ['any', *args] if nested:
+            return any(evaluate(arg, True) for arg in args)
+        case [variable, value] if nested:
+            v = ast.literal_eval(value)
+            x = evaluate_variable(variable)
+            return x == v
+        case [variable] if nested:
+            x = evaluate_variable(variable)
+            return x
+        case _:
+            raise ValueError

rust2rpm/tests/test_cfg.py

@@ -0,0 +1,60 @@
+import pytest
+
+from rust2rpm import cfg
+
+def test_pyparsing_run_tests():
+    g = cfg.cfg_grammar()
+
+    g.run_tests("""\
+    cfg(target_os = "macos")
+    cfg(any(foo, bar))
+    cfg(all(unix, target_pointer_width = "32"))
+    cfg(not(foo))
+    """)
+
+@pytest.mark.parametrize('expr, expected', [
+    ('cfg(target_os = "macos")',
+     False),
+    ('cfg(any(foo, bar))',
+     False),
+    ('cfg(all(unix, target_pointer_width = "16"))',
+     False),
+    ('cfg(not(foo))',
+     True),
+
+    ('cfg(unix)',
+     True),
+    ('cfg(not(unix))',
+     False),
+    ('cfg(windows)',
+     False),
+    ('cfg(linux)',   # not defined
+     False),
+    ('cfg(not(windows))',
+     True),
+    ('cfg(any(unix, windows))',
+     True),
+    ('cfg(any(windows, unix))',
+     True),
+    ('cfg(any(windows, windows, windows))',
+     False),
+
+    ('cfg(target_os = "linux")',
+     True),
+    ('cfg(any(target_os = "linux"))',
+     True),
+    ('cfg(all(target_os = "linux"))',
+     True),
+    ('cfg(any(target_os = "linux", target_os = "macos"))',
+     True),
+
+    ('cfg(any(target_pointer_width = "16", target_pointer_width = "32", target_pointer_width = "64"))',
+     True),
+    ('cfg(all(target_pointer_width = "16", target_pointer_width = "32", target_pointer_width = "64"))',
+     False),
+
+])
+def test_expressions(expr, expected):
+    parsed = cfg.cfg_grammar().parse_string(expr)
+    value = cfg.evaluate(parsed[0])
+    assert value == expected