[PATCH 6/9] scripts: add functionality to update wrap files from Cargo.lock

.wrap files and Cargo.lock contain pretty much the same information.
QEMU uses the former to make it easier for distros to use a local
registry, and also because Meson <1.13 does not use Cargo.lock for
the "meson subprojects" command.  This however introduces an
inconvenience when running "cargo update", in that the wrap
files have to be updated by hand.

Add the possibility to get new versions from Cargo.lock and not
just from a local registry, thus automating the update.

For now, only existing wrap files are modified.  This means
that semver-breaking updates need to be done (at least partly)
by hand; it is enough to rename the wrap file prior to running
the script.

While the need for this script is a lot smaller with Meson 1.13, it
would still remain useful for packages that have a patch directory.
Perhaps a bit overengineered, but since we have it...

Signed-off-by: Paolo Bonzini <[email protected]>
---
 scripts/get-wraps-from-cargo-registry.py | 77 +++++++++++++++++++++---
 1 file changed, 69 insertions(+), 8 deletions(-)

diff --git a/scripts/get-wraps-from-cargo-registry.py b/scripts/get-wraps-from-cargo-registry.py
index 636e4ba3474..b3ae5a2c284 100755
--- a/scripts/get-wraps-from-cargo-registry.py
+++ b/scripts/get-wraps-from-cargo-registry.py
@@ -3,7 +3,8 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 """
-get-wraps-from-cargo-registry.py - Update Meson subprojects from a global registry
+get-wraps-from-cargo-registry.py - Update Meson subprojects from a Cargo
+registry or from the versions pinned in Cargo.lock.
 """
 
 # Copyright (C) 2025 Red Hat, Inc.
@@ -18,6 +19,7 @@
 import shutil
 import subprocess
 import sys
+import tomllib
 
 
 def get_name_and_semver(namever: str) -> tuple[str, str]:
@@ -75,6 +77,49 @@ def rewrite_source(self, section: configparser.SectionProxy, orig_namever: str,
         return True
 
 
+class CargoLock(CrateSource):
+    """Locate crates by the versions pinned in a Cargo.lock file."""
+
+    origin = "crates.io"
+
+    def __init__(self, path: str):
+        with open(path, "rb") as f:
+            data = tomllib.load(f)
+
+        self.versions: dict[str, list[str]] = {}
+        self.checksums: dict[str, str] = {}
+        for pkg in data.get("package", []):
+            # workspace members have neither a checksum nor a crates.io tarball
+            if "checksum" not in pkg:
+                continue
+            name, version = pkg["name"], pkg["version"]
+            self.versions.setdefault(name, []).append(version)
+            self.checksums[f"{name}-{version}"] = pkg["checksum"]
+
+    def find(self, namever: str) -> str | None:
+        """Find pinned crate matching name and semver prefix"""
+        name, semver = get_name_and_semver(namever)
+        versions = sorted(self.versions.get(name, []))
+
+        # exact version match
+        if semver in versions:
+            return f"{name}-{semver}"
+
+        # semver match
+        matches = [v for v in versions if v.startswith(f"{semver}.")]
+        return f"{name}-{matches[0]}" if matches else None
+
+    def rewrite_source(self, section: configparser.SectionProxy, orig_namever: str, new_namever: str) -> bool:
+        # rewrite the download keys to fetch the pinned version from crates.io.
+        if orig_namever == new_namever:
+            return False
+        name, version = get_name_and_semver(new_namever)
+        section["source_url"] = f"https://crates.io/api/v1/crates/{name}/{version}/download"
+        section["source_filename"] = f"{new_namever}.tar.gz"
+        section["source_hash"] = self.checksums[new_namever]
+        return True
+
+
 class UpdateSubprojects:
     cargo_registry: str
     source: CrateSource
@@ -104,12 +149,13 @@ def compare_build_rs(self, orig_dir: str, source_namever: str) -> None:
             print("   This may affect the build process - please review the differences.")
 
     def update_subproject(self, wrap_file: str, source_namever: str) -> None:
-        """Modify [wrap-file] section to point to self.cargo_registry."""
+        """Modify [wrap-file] section to use the crate resolved as `source_namever`."""
         assert wrap_file.endswith("-rs.wrap")
         wrap_name = wrap_file[:-5]
 
         env = os.environ.copy()
-        env["MESON_PACKAGE_CACHE_DIR"] = self.cargo_registry
+        if self.cargo_registry:
+            env["MESON_PACKAGE_CACHE_DIR"] = self.cargo_registry
 
         config = configparser.ConfigParser()
         config.read(wrap_file)
@@ -157,9 +203,15 @@ def parse_cmdline() -> argparse.Namespace:
         parser = argparse.ArgumentParser(
             description="Replace Meson subprojects with packages in a Cargo registry"
         )
+        parser.add_argument(
+            "--cargo-lock",
+            action='store_true',
+            default=False,
+            help="Update wraps from Cargo.lock",
+        )
         parser.add_argument(
             "--cargo-registry",
-            default=os.environ.get("CARGO_REGISTRY"),
+            default=None,
             help="Path to Cargo registry (default: CARGO_REGISTRY env var)",
         )
         parser.add_argument(
@@ -170,9 +222,15 @@ def parse_cmdline() -> argparse.Namespace:
         )
 
         args = parser.parse_args()
-        if not args.cargo_registry:
-            print("error: CARGO_REGISTRY environment variable not set and --cargo-registry not provided")
+        if args.cargo_registry and args.cargo_lock:
+            print("error: --cargo-registry and --cargo-lock are incompatible")
             sys.exit(1)
+        if not args.cargo_registry and not args.cargo_lock:
+            args.cargo_registry = os.environ.get("CARGO_REGISTRY")
+            if not args.cargo_registry:
+                print("error: CARGO_REGISTRY environment variable not set and " +
+                      "--cargo-registry or --cargo-lock not provided")
+                sys.exit(1)
 
         return args
 
@@ -180,7 +238,10 @@ def __init__(self, args: argparse.Namespace):
         self.cargo_registry = args.cargo_registry
         self.dry_run = args.dry_run
         self.top_srcdir = os.getcwd()
-        self.source = CargoRegistry(args.cargo_registry)
+        if args.cargo_lock:
+            self.source = CargoLock(os.path.join(self.top_srcdir, "Cargo.lock"))
+        else:
+            self.source = CargoRegistry(args.cargo_registry)
 
     def main(self) -> None:
         if not os.path.exists("subprojects"):
@@ -193,7 +254,7 @@ def main(self) -> None:
 
             source_namever = self.source.find(namever)
             if not source_namever:
-                print(f"No installed crate found for {wrap_file}")
+                print(f"No crate found for {wrap_file}")
                 continue
 
             self.update_subproject(wrap_file, source_namever)
-- 
2.55.0