cargo: Warn when encountering unknown keys

Cargo sometimes adds new keys and Meson needs to gracefully handle
those. Currently, an unknown key will trigger an uncaught Python
exception, which is pretty much the worse case. With this change Meson
will instead issue a warning much like the one for unknown cpu
architectures.

See mesonbuild#13826 for the motivation for this change

mesonbuild/cargo/interpreter.py

@@ -54,6 +54,14 @@
     toml2json = shutil.which('toml2json')
 
 
+_EXTRA_KEYS_WARNING = (
+    "This may (unlikely) be an error in the cargo manifest, or may be a missing "
+    "implementation in Meson. If this issue can be reproduced with the latest "
+    "version of Meson, please help us by opening an issue at "
+    "https://github.com/mesonbuild/meson/issues. Please include the crate and "
+    "version that is generating this warning if possible."
+)
+
 class TomlImplementationMissing(MesonException):
     pass
 
@@ -160,6 +168,12 @@ def __post_init__(self) -> None:
     def from_raw(cls, raw: manifest.Package) -> Self:
         pkg = T.cast('manifest.FixedPackage',
                      {fixup_meson_varname(k): v for k, v in raw.items()})
+        unexpected = set(pkg) - {x.name for x in dataclasses.fields(cls)}
+        if unexpected:
+            mlog.warning("Package entry", pkg['name'], "has unexpected keys",
+                         '"{}".'.format(", ".join(sorted(unexpected))), _EXTRA_KEYS_WARNING)
+            for k in unexpected:
+                del pkg[k]
         return cls(**pkg)
 
 @dataclasses.dataclass
@@ -240,7 +254,16 @@ def from_raw(cls, name: str, raw: manifest.DependencyV) -> Dependency:
         """Create a dependency from a raw cargo dictionary"""
         if isinstance(raw, str):
             return cls(name, version.convert(raw))
-        return cls(name, **_fixup_raw_mappings(raw))
+        fixed = _fixup_raw_mappings(raw)
+
+        unexpected = set(fixed) - {x.name for x in dataclasses.fields(cls)}
+        if unexpected:
+            mlog.warning("Dependency entry", name, "has unexpected keys",
+                         '"{}".'.format(", ".join(sorted(unexpected))), _EXTRA_KEYS_WARNING)
+            for k in unexpected:
+                del fixed[k]
+
+        return cls(name, **fixed)
 
 
 @dataclasses.dataclass
@@ -274,6 +297,14 @@ class BuildTarget:
     @classmethod
     def from_raw(cls, raw: manifest.BuildTarget) -> Self:
         build = _fixup_raw_mappings(raw)
+
+        unexpected = set(build) - {x.name for x in dataclasses.fields(cls)}
+        if unexpected:
+            mlog.warning("Binary entry", build.get('name', '<anonymous>'), "has unexpected keys",
+                         '"{}".'.format(", ".join(sorted(unexpected))), _EXTRA_KEYS_WARNING)
+            for k in unexpected:
+                del build[k]
+
         return cls(**build)
 
 @dataclasses.dataclass
@@ -297,6 +328,13 @@ def from_raw(cls, raw: manifest.LibTarget, fallback_name: str) -> Self:
         if 'name' not in fixed:
             fixed['name'] = fallback_name
 
+        unexpected = set(fixed) - {x.name for x in dataclasses.fields(cls)}
+        if unexpected:
+            mlog.warning("Binary entry", fixed['name'], "has unexpected keys",
+                         '"{}".'.format(", ".join(sorted(unexpected))), _EXTRA_KEYS_WARNING)
+            for k in unexpected:
+                del fixed[k]
+
         return cls(**fixed)
 
 

test cases/rust/22 cargo subproject/subprojects/bar-0.1-rs/Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 name = "bar"
 version = "0.1"
+flooob = "lolz"
 
 # This dependency does not exist, it is required by default but this subproject
 # is called with default-features=false.

test cases/rust/22 cargo subproject/test.json

@@ -0,0 +1,8 @@
+{
+  "stdout": [
+    {
+      "line": "foo-0-rs| WARNING: Package entry bar has unexpected keys \"flooob\". This may (unlikely) be an error in the cargo manifest, or may be a missing implementation in Meson. If this issue can be reproduced with the latest version of Meson, please help us by opening an issue at https://github.com/mesonbuild/meson/issues. Please include the crate and version that is generating this warning if possible."
+    }
+  ]
+}
+