Fixes #4581: Failure to scan cargo

src/packagedcode/cargo.py

@@ -67,7 +67,13 @@ def assemble(cls, package_data, resource, codebase, package_adder):
                 package_data.extra_data[attribute] = 'workspace'
                 workspace_package_data[attribute] = getattr(package_data, attribute)
 
-        workspace_root_path = resource.parent(codebase).path
+        workspace_root = resource.parent(codebase)
+        if not workspace_root:
+            # If there's no parent (e.g., scanning a single file), use the directory part of the resource path
+            workspace_root_path = os.path.dirname(resource.path)
+        else:
+            workspace_root_path = workspace_root.path
+
         if workspace_package_data and workspace_members:
 
             # TODO: support glob patterns found in cargo workspaces
@@ -103,12 +109,14 @@ def assemble(cls, package_data, resource, codebase, package_adder):
                     package_adder=package_adder,
                 )
         else:
-            yield from cls.assemble_from_many_datafiles(
-                datafile_name_patterns=('Cargo.toml', 'cargo.toml', 'Cargo.lock', 'cargo.lock'),
-                directory=resource.parent(codebase),
-                codebase=codebase,
-                package_adder=package_adder,
-            )
+            parent_resource = resource.parent(codebase)
+            if parent_resource:
+                yield from cls.assemble_from_many_datafiles(
+                    datafile_name_patterns=('Cargo.toml', 'cargo.toml', 'Cargo.lock', 'cargo.lock'),
+                    directory=parent_resource,
+                    codebase=codebase,
+                    package_adder=package_adder,
+                )
 
     @classmethod
     def update_resource_package_data(cls, workspace, workspace_package_data, resource_package_data, mapping=None):

src/packagedcode/npm.py

@@ -125,7 +125,7 @@ def assemble(cls, package_data, resource, codebase, package_adder):
         workspace_root = package_resource.parent(codebase)
         workspace_root_path = None
         if workspace_root:
-            workspace_root_path = package_resource.parent(codebase).path
+            workspace_root_path = workspace_root.path
         workspaces = pkg_data.extra_data.get('workspaces') or []
 
         # Also look for pnpm workspaces

tests/packagedcode/data/cargo/cargo_toml/single-file-scan/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "constant_time_eq"
+version = "0.4.2"
+edition = "2024"
+authors = ["Cesar Eduardo Barros <cesarb@cesarb.eti.br>"]
+description = "Compares two equal-sized byte strings in constant time."
+documentation = "https://docs.rs/constant_time_eq"
+repository = "https://github.com/cesarb/constant_time_eq"
+readme = "README"
+keywords = ["constant_time"]
+categories = ["cryptography", "no-std"]
+license = "CC0-1.0 OR MIT-0 OR Apache-2.0"
+rust-version = "1.85.0"
+
+[dev-dependencies]
+criterion = { version = "0.5.1", features = ["cargo_bench_support", "html_reports"] }
+count_instructions = "0.2.0"

tests/packagedcode/data/cargo/cargo_toml/single-file-scan/Cargo.toml.expected

@@ -0,0 +1,126 @@
+{
+  "packages": [],
+  "dependencies": [],
+  "files": [
+    {
+      "path": "Cargo.toml",
+      "type": "file",
+      "package_data": [
+        {
+          "type": "cargo",
+          "namespace": null,
+          "name": "constant_time_eq",
+          "version": "0.4.2",
+          "qualifiers": {},
+          "subpath": null,
+          "primary_language": "Rust",
+          "description": "Compares two equal-sized byte strings in constant time.",
+          "release_date": null,
+          "parties": [
+            {
+              "type": "person",
+              "role": "author",
+              "name": "Cesar Eduardo Barros",
+              "email": "cesarb@cesarb.eti.br",
+              "url": null
+            }
+          ],
+          "keywords": [
+            "constant_time",
+            "cryptography",
+            "no-std"
+          ],
+          "homepage_url": null,
+          "download_url": null,
+          "size": null,
+          "sha1": null,
+          "md5": null,
+          "sha256": null,
+          "sha512": null,
+          "bug_tracking_url": null,
+          "code_view_url": null,
+          "vcs_url": "https://github.com/cesarb/constant_time_eq",
+          "copyright": null,
+          "holder": null,
+          "declared_license_expression": "cc0-1.0 OR mit-0 OR apache-2.0",
+          "declared_license_expression_spdx": "CC0-1.0 OR MIT-0 OR Apache-2.0",
+          "license_detections": [
+            {
+              "license_expression": "cc0-1.0 OR mit-0 OR apache-2.0",
+              "license_expression_spdx": "CC0-1.0 OR MIT-0 OR Apache-2.0",
+              "matches": [
+                {
+                  "license_expression": "cc0-1.0 OR mit-0 OR apache-2.0",
+                  "license_expression_spdx": "CC0-1.0 OR MIT-0 OR Apache-2.0",
+                  "from_file": "Cargo.toml",
+                  "start_line": 1,
+                  "end_line": 1,
+                  "matcher": "1-spdx-id",
+                  "score": 100.0,
+                  "matched_length": 10,
+                  "match_coverage": 100.0,
+                  "rule_relevance": 100,
+                  "rule_identifier": "spdx-license-identifier-cc0_1_0_or_mit_0_or_apache_2_0-f44a2ec174eb034bd3c662f728664281e507b20d",
+                  "rule_url": null,
+                  "matched_text": "CC0-1.0 OR MIT-0 OR Apache-2.0"
+                }
+              ],
+              "identifier": "cc0_1_0_or_mit_0_or_apache_2_0-3f14dd48-7cd8-cf28-d4e1-3b0174a587ee"
+            }
+          ],
+          "other_license_expression": null,
+          "other_license_expression_spdx": null,
+          "other_license_detections": [],
+          "extracted_license_statement": "CC0-1.0 OR MIT-0 OR Apache-2.0",
+          "notice_text": null,
+          "source_packages": [],
+          "file_references": [],
+          "is_private": false,
+          "is_virtual": false,
+          "extra_data": {
+            "documentation_url": "https://docs.rs/constant_time_eq",
+            "rust_version": "1.85.0",
+            "rust_edition": "2024"
+          },
+          "dependencies": [
+            {
+              "purl": "pkg:cargo/criterion",
+              "extracted_requirement": "0.5.1",
+              "scope": "dev-dependencies",
+              "is_runtime": false,
+              "is_optional": false,
+              "is_pinned": false,
+              "is_direct": true,
+              "resolved_package": {},
+              "extra_data": {
+                "version": "0.5.1",
+                "features": [
+                  "cargo_bench_support",
+                  "html_reports"
+                ]
+              }
+            },
+            {
+              "purl": "pkg:cargo/count_instructions",
+              "extracted_requirement": "0.2.0",
+              "scope": "dev-dependencies",
+              "is_runtime": false,
+              "is_optional": false,
+              "is_pinned": false,
+              "is_direct": true,
+              "resolved_package": {},
+              "extra_data": {}
+            }
+          ],
+          "repository_homepage_url": "https://crates.io/crates/constant_time_eq",
+          "repository_download_url": "https://crates.io/api/v1/crates/constant_time_eq/0.4.2/download",
+          "api_data_url": "https://crates.io/api/v1/crates/constant_time_eq",
+          "datasource_id": "cargo_toml",
+          "purl": "pkg:cargo/constant_time_eq@0.4.2"
+        }
+      ],
+      "for_packages": [],
+      "scan_errors": []
+    }
+  ]
+}

tests/packagedcode/test_cargo.py

@@ -83,6 +83,15 @@ def test_parse_cargo_toml_workspace_with_dependencies_child(self):
         packages_data = cargo.CargoTomlHandler.parse(test_file)
         self.check_packages_data(packages_data, expected_loc, regen=REGEN_TEST_FIXTURES)
 
+    def test_parse_cargo_toml_single_file_no_crash(self):
+        test_file = self.get_test_loc('cargo/cargo_toml/single-file-scan/Cargo.toml')
+        expected_file = self.get_test_loc('cargo/cargo_toml/single-file-scan/Cargo.toml.expected')
+        result_file = self.get_temp_file('results.json')
+        run_scan_click(['--package', test_file, '--json', result_file])
+        check_json_scan(
+            expected_file, result_file, remove_uuid=True, regen=REGEN_TEST_FIXTURES
+        )
+
     def test_parse_cargo_toml_tauri_workspace_in_version(self):
         test_file = self.get_test_loc('cargo/cargo_toml/tauri-examples/Cargo.toml')
         expected_loc = self.get_test_loc('cargo/cargo_toml/tauri-examples/Cargo.toml.expected')