rules: Improve merge script

- Merge section with same header, independently of the whitespaces.
- Improve Python (typing)

Part-of: <https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/merge_requests/728>

1 files changed, 45 insertions, 26 deletions

diff --git a/rules/merge.py b/rules/merge.py
index bdf21269..868879f3 100755
--- a/rules/merge.py
+++ b/rules/merge.py
@@ -1,11 +1,32 @@
 #!/usr/bin/env python3
+# SPDX-License-Identifier: MIT
+
+from __future__ import annotations
 
 import argparse
 import sys
+from collections import defaultdict
+from contextlib import AbstractContextManager, nullcontext
+from dataclasses import dataclass
 from pathlib import Path
+from typing import TextIO, cast
+
+
+@dataclass
+class Header:
+    text: str
+    key: tuple[str, ...]
+
+    @classmethod
+    def empty(cls) -> Header:
+        return Header("", ())
+
+    @classmethod
+    def parse(cls, raw: str) -> Header:
+        return Header(raw, tuple(raw.split()))
 
 
-def handle_file(path):
+def handle_file(path: Path) -> tuple[Header, Path]:
     """
     Return a tuple of (header, path) for the file at path.
     If the file does not have a header, the header is the empty string.
@@ -13,12 +34,12 @@ def handle_file(path):
     with open(path) as fd:
         header = fd.readline()
         if header.startswith("! "):
-            return header, path
+            return Header.parse(header), path
         else:
-            return "", path
+            return Header.empty(), path
 
 
-def merge(dest, files):
+def merge(dest: TextIO, files):
     """
     Merge the content of all files into the file dest.
 
@@ -31,7 +52,7 @@ def merge(dest, files):
     as header, these need to get written out first.
     """
 
-    def sort_basename(path):
+    def sort_basename(path: Path) -> str:
         return path.name
 
     # sort the file list by basename
@@ -41,43 +62,41 @@ def merge(dest, files):
     # out. We use section_names to keep the same order as we get the files
     # passed in (superfluous with python 3.6+ since the dict keeps the
     # insertion order anyway).
-    sections = {"": []}
-    section_names = [""]
+    sections: dict[tuple[str, ...], list[Path]] = defaultdict(list)
+    section_names = [Header.empty()]
     for path in files:
         # files may exist in srcdir or builddir, depending whether they're
         # generated
         header, path = handle_file(path)
-        paths = sections.get(header, [])
-        paths.append(path)
-        sections[header] = paths
-        if header not in section_names:
+        if header.key not in sections:
             section_names.append(header)
+        sections[header.key].append(path)
 
     for header in section_names:
-        if header:
+        if header.text:
             dest.write("\n")
-            dest.write(header)
-        for f in sections[header]:
+            dest.write(header.text)
+        for f in sections[header.key]:
             with open(f) as fd:
-                if header:
+                if header.text:
                     fd.readline()  # drop the header
                 dest.write(fd.read())
 
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser("rules file merge script")
-    parser.add_argument("--dest", type=str, default=None)
-    parser.add_argument("--srcdir", type=str)
-    parser.add_argument("--builddir", type=str)
-    parser.add_argument("files", nargs="+", type=str)
+    parser.add_argument("--dest", type=Path, default=None)
+    parser.add_argument("--srcdir", type=Path)
+    parser.add_argument("--builddir", type=Path)
+    parser.add_argument("files", nargs="+", type=Path)
     ns = parser.parse_args()
 
     if ns.dest is None:
-        dest = sys.stdout
+        dest: AbstractContextManager = nullcontext(sys.stdout)
     else:
-        dest = ns.dest
+        dest = cast(Path, ns.dest).open("wt")
 
-    with dest or open(dest, "w") as fd:
+    with dest as fd:
         basename = Path(sys.argv[0]).name
         fd.write(
             "// DO NOT EDIT THIS FILE - IT WAS AUTOGENERATED BY {} FROM rules/*.part\n".format(
@@ -86,15 +105,15 @@ if __name__ == "__main__":
         )
         fd.write("//\n")
 
-        def find_file(f):
+        def find_file(f: Path) -> Path:
             if ns.builddir:
-                path = Path(ns.builddir) / f
+                path = cast(Path, ns.builddir) / f
                 if path.exists():
                     return path
             if ns.srcdir:
-                path = Path(ns.srcdir) / f
+                path = cast(Path, ns.srcdir) / f
                 if path.exists():
                     return path
-            return Path(f)
+            return f
 
         merge(fd, [find_file(f) for f in ns.files])