Merge pull request #186 from packit/parsing

Avoid parsing the spec file over and over in loops

This fixes performance regression introduced in 9e1762c. Before every macro expansion, the spec file is parsed to be sure the global macro context is up-to-date, however, parsing of sections now calls macro expansion in a loop, and that can cause a huge performance hit.
Initially, I tried to implement caching, to parse only if the content of the spec file or some parsing parameters have changed, but then I realized sources affect parsing as well, and it's not even possible to get a list of sources without parsing.

Reviewed-by: Jiri Popelka <None>

Author: softwarefactory-project-zuul[bot]

specfile/sections.py

@@ -230,7 +230,12 @@ def parse(
 
         def expand(s):
             if context:
-                return context.expand(s)
+                result = context.expand(
+                    s, skip_parsing=getattr(expand, "skip_parsing", False)
+                )
+                # parse only once
+                expand.skip_parsing = True
+                return result
             return Macros.expand(s)
 
         def split_id(line):

specfile/specfile.py

@@ -158,19 +158,26 @@ def save(self) -> None:
         self.path.write_text(str(self))
 
     def expand(
-        self, expression: str, extra_macros: Optional[List[Tuple[str, str]]] = None
+        self,
+        expression: str,
+        extra_macros: Optional[List[Tuple[str, str]]] = None,
+        skip_parsing: bool = False,
     ) -> str:
         """
         Expands an expression in the context of the spec file.
 
         Args:
             expression: Expression to expand.
             extra_macros: Extra macros to be defined before expansion is performed.
+            skip_parsing: Do not parse the spec file before expansion is performed.
+              Defaults to False. Mutually exclusive with extra_macros. Set this to True
+              only if you are certain that the global macro context is up-to-date.
 
         Returns:
             Expanded expression.
         """
-        self._parser.parse(str(self), extra_macros)
+        if not skip_parsing:
+            self._parser.parse(str(self), extra_macros)
         return Macros.expand(expression)
 
     def get_active_macros(self) -> List[Macro]:

specfile/value_parser.py

@@ -312,7 +312,12 @@ def construct_regex(
 
         def expand(s):
             if context:
-                return context.expand(s)
+                result = context.expand(
+                    s, skip_parsing=getattr(expand, "skip_parsing", False)
+                )
+                # parse only once
+                expand.skip_parsing = True
+                return result
             return Macros.expand(s)
 
         def flatten(nodes):

tests/unit/test_sections.py

@@ -60,7 +60,7 @@ def test_parse():
             "0",
             "%changelog",
         ],
-        context=flexmock(expand=lambda s: "\n" if s == "%{desc}" else ""),
+        context=flexmock(expand=lambda s, **_: "\n" if s == "%{desc}" else ""),
     )
     assert sections[0][0] == "0"
     assert sections[1].id == "description"