build: add script for collecting dependencies (make requires)

Makefile

@@ -6,7 +6,7 @@ BINDIR     ?= $(PREFIX)/bin
 DATADIR    ?= $(PREFIX)/share
 LIBEXECDIR ?= $(PREFIX)/libexec
 
-.PHONY: build clean install check
+.PHONY: build clean install check requires
 .DEFAULT: build
 
 GENERATED := $(patsubst %.in,%,$(wildcard sway/*.in sway/*/*.in ))
@@ -47,3 +47,6 @@ check:
 	mkdir -p test
 	export WLR_BACKENDS=headless WLR_RENDERER=pixman XDG_RUNTIME_DIR="$(CURDIR)/test" SRCDIR="$(CURDIR)"; \
 		/usr/bin/sway --debug --validate --config $(CURDIR)/sway/config.test
+
+requires: | build
+	@./scripts/requires.py sway/config

scripts/requires.py

@@ -0,0 +1,129 @@
+#!/usr/bin/python3
+"""
+Collect the dependency specification comments from a sway config,
+following the `include` directives.
+
+The script can handle the declaration style we use in this project:
+```
+# Requires: the-package
+# Recommends: the-other-package
+```
+but it is in no way a complete sway config parser (or a complete
+rpm-style dependency parser).
+"""
+
+from __future__ import annotations
+
+import logging
+import re
+import sys
+from dataclasses import dataclass
+from glob import iglob
+from os.path import abspath, basename, expandvars, relpath
+from typing import Sequence
+
+LOG = logging.getLogger()
+# Resolve paths without actually installing the snippets
+MAPPINGS = {  #
+    "/etc/sway/config.d": abspath("sway"),
+    "/usr/share/sway/config.d": abspath("sway/config.d"),
+}
+INCLUDE_RE = re.compile(r"^include\s+(.*?)\s*$")
+DIRECTIVE_RE = re.compile(r"^#\s*([A-Z]\w+):\s*(.*)\s*$")
+DEPENDENCY_RE = re.compile(r"^([^\s<=>]+)")
+DEPENDENCY_SEP_RE = re.compile(r",\s*")
+
+files: set[str] = set()
+dependencies: dict[str, Dependency] = {}
+
+
+@dataclass
+class Dependency:
+    """RPM-style dependency specification"""
+
+    __raw: str
+    name: str
+    weak: bool = False
+
+    def __init__(self, raw: str, weak: bool = False):
+        self.__raw = raw
+        self.weak = weak
+        if match := DEPENDENCY_RE.match(raw):
+            self.name = match[1]
+        else:
+            raise Exception(f"Failed to parse dependency spec {raw}")
+
+    def __hash__(self):
+        return self.name.__hash__()
+
+    def __lt__(self, other):
+        """Sort order: weak deps first, then alphabetic"""
+        return self.weak if self.weak != other.weak else self.name < other.name
+
+    def __str__(self):
+        return ("Recommends: " if self.weak else "Requires: ") + self.__raw
+
+    def stronger(self, other: Dependency):
+        """
+        Checks that the current dependency is for the same package, but
+        stronger than the other.
+        """
+        if self.name != other.name:
+            return False
+
+        return other.weak and not self.weak
+
+    @staticmethod
+    def parse(string: str, **args) -> Sequence[Dependency]:
+        """Read one or multiple dependency specifications from string"""
+        return [Dependency(v, **args) for v in DEPENDENCY_SEP_RE.split(string)]
+
+
+def handle_directive(directive: str, value: str):
+    if directive in ("Requires", "Recommends"):
+        weak = directive == "Recommends"
+        for dependency in Dependency.parse(value, weak=weak):
+            existing = dependencies.get(dependency.name, None)
+            if existing and not dependency.stronger(existing):
+                continue
+            dependencies[dependency.name] = dependency
+
+
+def handle_include(value: str, root_dir: str = None):
+    # hack to support scripts/sway/layered-include
+    if value.startswith("'$("):
+        value = abspath("sway/config.d/*.conf")
+    value = expandvars(value)
+    for prefix, subst in MAPPINGS.items():
+        if value.startswith(prefix):
+            value = value.replace(prefix, subst)
+    for inc in iglob(value, root_dir=root_dir):
+        handle_file(inc)
+
+
+def handle_file(path: str):
+    """Parse configuration snippet file"""
+    if path in files:
+        return
+    files.add(path)
+    LOG.info("processing %s", relpath(path))
+
+    try:
+        with open(path, "r", encoding="utf-8") as file:
+            for line in file:
+                if match := INCLUDE_RE.match(line):
+                    handle_include(match[1], basename(path))
+                elif match := DIRECTIVE_RE.match(line):
+                    handle_directive(match[1], match[2])
+    except IOError:
+        LOG.exception("Failed to read %s", path)
+
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.DEBUG)
+
+    for arg in sys.argv[1:]:
+        handle_file(arg)
+
+    for dep in sorted(dependencies.values()):
+        print(dep)