Add support for conditionally processing headers

Author: virtuald

pyproject.toml

@@ -25,6 +25,7 @@ dependencies = [
     "sphinxify >= 0.7.3",
     "validobj ~= 1.2",
     "cxxheaderparser[pcpp] ~= 1.5",
+    "packaging",
     "tomli",
     "tomli_w",
     "toposort",

src/semiwrap/config/pyproject_toml.py

@@ -4,7 +4,7 @@
 
 import dataclasses
 import re
-from typing import Dict, List, Optional
+from typing import Dict, List, Optional, Union
 
 _arch_re = re.compile(r"\{\{\s*ARCH\s*\}\}")
 _os_re = re.compile(r"\{\{\s*OS\s*\}\}")
@@ -60,6 +60,28 @@ class TypeCasterConfig:
     headers: List[TypeCasterHeader] = dataclasses.field(default_factory=list)
 
 
+@dataclasses.dataclass
+class ConditionalHeader:
+    """
+    Allows specifying that a header will only be autogenerated if the specified
+    condition is true.
+
+    .. code-block:: toml
+
+        [tool.semiwrap.extension_modules."PACKAGE.NAME".headers]
+        Name = { header="header.h", enable_if = "platform_machine == 'aarch64'" }
+
+    """
+
+    #: Name of the header file
+    header: str
+
+    #: This is a PEP 508 environment marker specification.
+    #:
+    #: The header will not be parsed if this does not evaluate to true
+    enable_if: str
+
+
 @dataclasses.dataclass
 class ExtensionModuleConfig:
     """
@@ -123,7 +145,9 @@ class ExtensionModuleConfig:
     #:
     #: .. seealso:: :ref:`autowrap`
     #:
-    headers: Dict[str, str] = dataclasses.field(default_factory=dict)
+    headers: Dict[str, Union[str, ConditionalHeader]] = dataclasses.field(
+        default_factory=dict
+    )
 
     #: Path to a directory of yaml files. Generation data will be looked up
     #: using the key in the headers dictionary.

src/semiwrap/pyproject.py

@@ -1,6 +1,7 @@
 import pathlib
 import typing as T
 
+import packaging.markers
 import tomli
 
 from .config.util import parse_input
@@ -21,6 +22,19 @@ def __init__(self, pyproject_path: T.Optional[pathlib.Path] = None) -> None:
 
         self._all_deps = None
 
+        self._evaluated_markers: T.Dict[str, bool] = {}
+
+    def _enable_if(self, condition: str) -> bool:
+        """
+        Evaluates a string containing PEP 508 environment markers
+        """
+        ok = self._evaluated_markers.get(condition)
+        if ok is None:
+            ok = packaging.markers.Marker(condition).evaluate()
+            self._evaluated_markers[condition] = ok
+
+        return ok
+
     @property
     def package_root(self) -> pathlib.Path:
         if self._package_root is None:
@@ -71,3 +85,12 @@ def get_extension_deps(self, extension: ExtensionModuleConfig) -> T.List[str]:
                 deps.append(wrap)
         deps.extend(extension.depends)
         return deps
+
+    def get_extension_headers(
+        self, extension: ExtensionModuleConfig
+    ) -> T.Generator[T.Tuple[str, str], None, None]:
+        for yml, hdr in extension.headers.items():
+            if isinstance(hdr, str):
+                yield yml, hdr
+            elif self._enable_if(hdr.enable_if):
+                yield yml, hdr.header

src/semiwrap/tool/scan_headers.py

@@ -80,9 +80,15 @@ def _should_ignore(f):
                             all_present.add(inc / h.header)
 
             for name, ext in project.extension_modules.items():
-                if not ext.headers:
+                files = []
+                for _, f in ext.headers.items():
+                    if isinstance(f, str):
+                        files.append(Path(f))
+                    else:
+                        files.append(Path(f.header))
+
+                if not files:
                     continue
-                files = [Path(f) for f in ext.headers.values()]
                 for incdir in search_paths[name]:
                     incdir = Path(incdir)
                     for f in files:

tests/cpp/sw-test/pyproject.toml

@@ -65,6 +65,10 @@ using2 = "using2.h"
 virtual_comma = "virtual_comma.h"
 virtual_xform = "virtual_xform.h"
 
+# conditional headers
+cond_always_true = { header="cond_always_true.h", enable_if="python_version > '2'"}
+cond_never_true = { header="cond_never_true.h", enable_if="python_version < '2'"}
+
 # Inheritance
 IBase = "inheritance/ibase.h"
 IChild = "inheritance/ichild.h"

tests/cpp/sw-test/semiwrap/ft/cond_always_true.yml

@@ -0,0 +1,4 @@
+---
+
+functions:
+  always_compiled:

tests/cpp/sw-test/src/swtest/ft/include/cond_always_true.h

@@ -0,0 +1,3 @@
+#pragma once
+
+inline int always_compiled() { return 1; }

tests/cpp/sw-test/src/swtest/ft/include/cond_never_true.h

@@ -0,0 +1 @@
+#error "Should never be compiled"