cargo: convert TOMLDecodeError or toml2json errors to a MesonException

Avoid getting a raw exception, instead use a (subclass of) MesonException
that is printed in the usual "FILE:LINE:COLUMN: MESSAGE" format.

Fixes: #15023
Signed-off-by: Paolo Bonzini <[email protected]>

Author: bonzini

mesonbuild/cargo/toml.py

@@ -31,17 +31,27 @@ class TomlImplementationMissing(MesonException):
     pass
 
 
+class CargoTomlError(MesonException):
+    """Exception for TOML parsing errors, keeping proper location info."""
+
+
 def load_toml(filename: str) -> T.Dict[str, object]:
     if tomllib:
-        with open(filename, 'rb') as f:
-            raw = tomllib.load(f)
+        try:
+            with open(filename, 'rb') as f:
+                raw = tomllib.load(f)
+        except tomllib.TOMLDecodeError as e:
+            raise CargoTomlError(e.msg, file=filename, lineno=e.lineno, colno=e.colno) from e
+        except Exception:
+            raise
     else:
         if toml2json is None:
             raise TomlImplementationMissing('Could not find an implementation of tomllib, nor toml2json')
 
         p, out, err = Popen_safe([toml2json, filename])
         if p.returncode != 0:
-            raise MesonException('toml2json failed to decode output\n', err)
+            error_msg = err.strip() or 'toml2json failed to decode TOML'
+            raise CargoTomlError(error_msg, file=filename)
 
         raw = json.loads(out)
 

test cases/failing/136 cargo toml error/meson.build

@@ -0,0 +1,15 @@
+project('cargo-toml-error', 'c')
+
+# Check if we have tomllib/tomli (not toml2json)
+python = find_program('python3', 'python')
+result = run_command(python, '-c', 'import tomllib', check: false)
+if result.returncode() != 0
+  result = run_command(python, '-c', 'import tomli', check: false)
+  if result.returncode() != 0
+    # Skip test if using toml2json - error format will be different
+    error('MESON_SKIP_TEST toml2json in use, skipping test')
+  endif
+endif
+
+# This should trigger a CargoTomlError with proper location info
+foo_dep = dependency('foo-0')

test cases/failing/136 cargo toml error/subprojects/foo-0-rs.wrap

@@ -0,0 +1,5 @@
+[wrap-file]
+method = cargo
+
+[provide]
+dependency_names = foo-0

test cases/failing/136 cargo toml error/subprojects/foo-0-rs/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "foo"
+version = "0.0.1"
+edition = "2021"
+# This creates a TOML decode error: duplicate key
+name = "bar"

test cases/failing/136 cargo toml error/test.json

@@ -0,0 +1,7 @@
+{
+  "stdout": [
+    {
+      "line": "test cases/failing/136 cargo toml error/subprojects/foo-0-rs/Cargo.toml:6:13: ERROR: Cannot overwrite a value"
+    }
+  ]
+}