Prevent recursive macro expansion loops

pyrpm/spec.py

@@ -1,12 +1,6 @@
 """Python module for parsing RPM spec files.
 
-RPMs are build from a package's sources along with a spec file. The spec file controls how the RPM
-is built. This module allows you to parse spec files and gives you simple access to various bits of
-information that is contained in the spec file.
-
-Current status: This module does not parse everything of a spec file. Only the pieces I needed. So
-there is probably still plenty of stuff missing. However, it should not be terribly complicated to
-add support for the missing pieces.
+This module allows to parse RPM spec files and gives simple access to various bits of information contained in the spec file.
 
 """
 
@@ -125,13 +119,27 @@ def __init__(self, name: str, pattern_obj: re.Pattern) -> None:
 
     def update_impl(self, spec_obj: "Spec", context: Dict[str, Any], match_obj: re.Match, line: str) -> Tuple["Spec", dict]:
         name, value = match_obj.groups()
-        spec_obj.macros[name] = str(value)
+        raw_value = str(value)
+        stored_value = raw_value
+        if _macro_references_itself(raw_value, name):
+            try:
+                stored_value = replace_macros(raw_value, spec_obj)
+            except RuntimeError:
+                stored_value = raw_value
+        spec_obj.macros[name] = stored_value
         if name not in _tag_names:
             # Also make available as attribute of spec object
-            setattr(spec_obj, name, str(value))
+            setattr(spec_obj, name, stored_value)
         return spec_obj, context
 
 
+def _macro_references_itself(raw_value: str, macro_name: str) -> bool:
+    """Check if a macro definition references itself."""
+    brace_pattern = rf"(?<!%)%{{{re.escape(macro_name)}}}"
+    bare_pattern = rf"(?<!%)%{re.escape(macro_name)}\b"
+    return bool(re.search(brace_pattern, raw_value) or re.search(bare_pattern, raw_value))
+
+
 class _List(_Tag):
     """Parse a tag that expands to a list."""
 
@@ -332,8 +340,8 @@ def __init__(self, name: str) -> None:
         assert isinstance(name, str)
         self.line = name
         self.name: str
-        self.operator: Optional[str]
-        self.version: Optional[str]
+        self.operator: str | None
+        self.version: str | None
         match = Requirement.expr.match(name)
         if match:
             self.name = match.group(1)
@@ -436,9 +444,9 @@ def __init__(self) -> None:
 
         self.sources_dict: Dict[str, str] = {}
         self.patches_dict: Dict[str, str] = {}
-        self.macros: Dict[str, str] = {}
+        self.macros: Dict[str, str] = {"nil": ""}
 
-        self.name: Optional[str]
+        self.name: str | None
         self.packages: List[Package] = []
 
     @property
@@ -486,6 +494,9 @@ def from_string(cls, string: str) -> "Spec":
 def replace_macros(string: str, spec: Spec, max_attempts: int = 1000) -> str:
     """Replace all macros in given string with corresponding values.
 
+    Note: If macros are not defined in the spec file, this won't try to
+    expand them.
+
     For example, a string '%{name}-%{version}.tar.gz' will be transformed to 'foo-2.0.tar.gz'.
 
     :param string A string containing macros that you want to be replaced.
@@ -537,18 +548,15 @@ def get_replacement_string(match: re.Match) -> str:
                 if len(parts) == 2:
                     return parts[1]
 
-                return spec.macros.get(macro, getattr(spec, macro))
+                return spec.macros.get(macro, getattr(spec, macro, ""))
 
         if spec:
             value = spec.macros.get(macro_name, getattr(spec, macro_name, None))
-            if value:
+            if value is not None:
                 return str(value)
 
         return match.string[match.start() : match.end()]
 
-    # Recursively expand macros.
-    # Note: If macros are not defined in the spec file, this won't try to
-    # expand them.
     attempt = 0
     ret = ""
     while attempt < max_attempts:

requirements.txt

@@ -3,6 +3,7 @@ coverage==7.11.0
 flit==3.12.0
 mypy==1.18.2
 pylint==4.0.2
+pytest-asyncio==1.2.0
 pytest-cov==7.0.0
 pytest==8.4.2
 rope==1.14.0