build: Turn version.py into idiomatic Python

While it's possible to write C code in Python, it's better to actually
write Python code in Python.

Use regular expressions, instead of counting characters, to allow a
little bit more leeway when editing the cairo-version.h header file.

Use a context manager to handle the lifetime of a file object.

Use f-strings instead of the obsolete format() method.

1 files changed, 41 insertions, 19 deletions

diff --git a/version.py b/version.py
index 7e0ded0d7..aabc20593 100755
--- a/version.py
+++ b/version.py
@@ -5,27 +5,49 @@
 # Extracts the version from cairo-version.h for the meson build files.
 #
 import os
+import re
 import sys
 
-if __name__ == '__main__':
-    srcroot = os.path.dirname(__file__)
 
-    version_major = None
-    version_minor = None
-    version_micro = None
+MAJOR_RE = re.compile(
+    r'^\s*#\s*define\s+CAIRO_VERSION_MAJOR\s+(?P<number>[0-9]+)\s*$',
+    re.UNICODE)
 
-    f = open(os.path.join(srcroot, 'src', 'cairo-version.h'), 'r', encoding='utf-8')
+MINOR_RE = re.compile(
+    r'^\s*#\s*define\s+CAIRO_VERSION_MINOR\s+(?P<number>[0-9]+)\s*$',
+    re.UNICODE)
+
+MICRO_RE = re.compile(
+    r'^\s*#\s*define\s+CAIRO_VERSION_MICRO\s+(?P<number>[0-9]+)\s*$',
+    re.UNICODE)
+
+version_major = None
+version_minor = None
+version_micro = None
+
+srcroot = os.path.dirname(__file__)
+version_h = os.path.join(srcroot, "src", "cairo-version.h")
+
+with open(version_h, "r", encoding="utf-8") as f:
     for line in f:
-        if line.startswith('#define CAIRO_VERSION_MAJOR '):
-            version_major = line[28:].strip()
-        if line.startswith('#define CAIRO_VERSION_MINOR '):
-            version_minor = line[28:].strip()
-        if line.startswith('#define CAIRO_VERSION_MICRO '):
-            version_micro = line[28:].strip()
-    f.close()
-
-    if not (version_major and version_minor and version_micro):
-       print('ERROR: Could not extract cairo version from cairo-version.h in', srcroot, file=sys.stderr)
-       sys.exit(-1)
-
-    print('{0}.{1}.{2}'.format(version_major, version_minor, version_micro))
+        res = MAJOR_RE.match(line)
+        if res:
+            assert version_major is None
+            version_major = res.group('number')
+            continue
+        res = MINOR_RE.match(line)
+        if res:
+            assert version_minor is None
+            version_minor = res.group('number')
+            continue
+        res = MICRO_RE.match(line)
+        if res:
+            assert version_micro is None
+            version_micro = res.group('number')
+            continue
+
+if not (version_major and version_minor and version_micro):
+    print(f"ERROR: Could not extract version from cairo-version.h in {srcroot}", file=sys.stderr)  # noqa
+    sys.exit(-1)
+
+print(f"{version_major}.{version_minor}.{version_micro}")