Fix preprocessor option to retain content

cxxheaderparser/preprocessor.py

@@ -3,6 +3,7 @@ Contains optional preprocessor support via pcpp
 """
 
 import io
+import os
 from os.path import relpath
 import typing
 from .options import PreprocessorFunction
@@ -17,7 +18,7 @@ class PreprocessorError(Exception):
 class _CustomPreprocessor(Preprocessor):
     def __init__(self):
         Preprocessor.__init__(self)
-        self.errors = []
+        self.errors: typing.List[str] = []
 
     def on_error(self, file, line, msg):
         self.errors.append(f"{file}:{line} error: {msg}")
@@ -34,21 +35,15 @@ def _filter_self(fname: str, fp: typing.TextIO) -> str:
     # isn't what a typical user of cxxheaderparser would want, so we strip out
     # the line directives and any content that isn't in our original file
 
-    # Compute the filename to match based on how pcpp does it
-    try:
-        relfname = relpath(fname)
-    except Exception:
-        relfname = fname
-    relfname = relfname.replace("\\", "/")
-
-    relfname += '"\n'
+    # pcpp always emits line directives that match whatever is passed in to it
+    line_ending = f'{fname}"\n'
 
     new_output = io.StringIO()
     keep = True
 
     for line in fp:
         if line.startswith("#line"):
-            keep = line.endswith(relfname)
+            keep = line.endswith(line_ending)
 
         if keep:
             new_output.write(line)

tests/test_preprocessor.py

@@ -1,7 +1,17 @@
+import pathlib
+
 from cxxheaderparser.options import ParserOptions
 from cxxheaderparser.preprocessor import make_pcpp_preprocessor
-from cxxheaderparser.simple import NamespaceScope, ParsedData, parse_string
-from cxxheaderparser.types import FundamentalSpecifier, NameSpecifier, PQName, Token, Type, Value, Variable
+from cxxheaderparser.simple import NamespaceScope, ParsedData, parse_file, parse_string
+from cxxheaderparser.types import (
+    FundamentalSpecifier,
+    NameSpecifier,
+    PQName,
+    Token,
+    Type,
+    Value,
+    Variable,
+)
 
 
 def test_basic_preprocessor() -> None:
@@ -24,4 +34,33 @@ def test_basic_preprocessor() -> None:
                 )
             ]
         )
-    )
+    )
+
+
+def test_preprocessor_omit_content(tmp_path: pathlib.Path) -> None:
+    """Ensure that content in other headers is omitted"""
+    h_content = '#include "t2.h"' "\n" "int x = X;\n"
+    h2_content = "#define X 2\n" "int omitted = 1;\n"
+
+    with open(tmp_path / "t1.h", "w") as fp:
+        fp.write(h_content)
+
+    with open(tmp_path / "t2.h", "w") as fp:
+        fp.write(h2_content)
+
+    options = ParserOptions(preprocessor=make_pcpp_preprocessor())
+    data = parse_file(tmp_path / "t1.h", options=options)
+
+    assert data == ParsedData(
+        namespace=NamespaceScope(
+            variables=[
+                Variable(
+                    name=PQName(segments=[NameSpecifier(name="x")]),
+                    type=Type(
+                        typename=PQName(segments=[FundamentalSpecifier(name="int")])
+                    ),
+                    value=Value(tokens=[Token(value="2")]),
+                )
+            ]
+        )
+    )