recognize inline Cargo lint tables

Author: tartakovsky

.worklogs/2026-07-12-003740-cargo-inline-lint-tables.md

@@ -0,0 +1,21 @@
+# Cargo inline lint tables
+
+## Summary
+
+The Cargo engine now recognizes standard and inline TOML tables as package-local lint-table identities. Exact-empty and required-table requirements therefore match every Cargo-supported table syntax.
+
+## Decisions made
+
+- Kept syntax recognition in the Cargo engine because `[lints.<tool>]` identity is Cargo-specific.
+- Reused one predicate for required, forbidden, and exact reconciliation.
+- Added direct regressions for required and exact-empty behavior.
+
+## Key files for context
+
+- `packages/file-types/toml/aqc-cargo-toml-engine/src/reconcile/package_lint_tables.rs`
+- `packages/file-types/toml/aqc-cargo-toml-engine/tests/package_lint_tables.rs`
+- `packages/file-types/toml/aqc-rust-toolchain-toml-engine/tests/behavior.rs`
+
+## Next steps
+
+- Publish `aqc-cargo-toml-engine 0.5.2` and refresh downstream locks.

packages/file-types/toml/aqc-cargo-toml-engine/Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "aqc-cargo-toml-engine"
-version = "0.5.1"
+version = "0.5.2"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.85"

packages/file-types/toml/aqc-cargo-toml-engine/Cargo.toml

@@ -17,8 +17,8 @@ pub(crate) fn apply(
             .flat_map(|items| items.iter())
             .filter(|(tool, _)| !requirements.required.contains_key(*tool)),
     ) {
-        let present = table_ref(doc, "lints")
-            .is_some_and(|table| table.get(tool).is_some_and(Item::is_table_like));
+        let present =
+            table_ref(doc, "lints").is_some_and(|table| table.get(tool).is_some_and(is_lint_table));
         if present {
             continue;
         }
@@ -38,7 +38,7 @@ pub(crate) fn apply(
         .map(|table| {
             table
                 .iter()
-                .filter(|(_, item)| item.is_table_like())
+                .filter(|(_, item)| is_lint_table(item))
                 .map(|(key, _)| key.to_owned())
                 .collect::<Vec<_>>()
         })
@@ -87,6 +87,11 @@ pub(crate) fn apply(
     }
 }
 
+/// Cargo accepts package-local lint groups as standard or inline TOML tables.
+fn is_lint_table(item: &Item) -> bool {
+    item.is_table_like() || item.as_inline_table().is_some()
+}
+
 /// Remove one local lint table while preserving the surrounding `[lints]` table.
 fn remove_table(doc: &mut DocumentMut, tool: &str) {
     if let Some(table) = doc.get_mut("lints").and_then(Item::as_table_like_mut) {

packages/file-types/toml/aqc-cargo-toml-engine/src/reconcile/package_lint_tables.rs

@@ -95,6 +95,18 @@ fn required_table_accepts_an_existing_table() {
     assert!(findings.is_empty());
 }
 
+#[test]
+fn required_table_accepts_an_existing_inline_table() {
+    let findings = cargo_findings_with(
+        Some(b"[lints]\nrust = { unsafe_code = \"forbid\" }\n"),
+        vec![(
+            prov("rust"),
+            table_requirements(vec![("rust", "need rust")], Vec::new(), None),
+        )],
+    );
+    assert!(findings.is_empty());
+}
+
 #[test]
 fn forbidden_table_reports_only_the_named_table() {
     let findings = cargo_findings_with(
@@ -124,6 +136,20 @@ fn exact_empty_reports_each_local_lint_table_separately() {
     assert_eq!(mismatch_count_for_key(&findings, "[lints.clippy]"), 1);
 }
 
+#[test]
+fn exact_empty_reports_inline_local_lint_tables() {
+    let findings = cargo_findings_with(
+        Some(b"[lints]\nrust = { unsafe_code = \"forbid\" }\n"),
+        vec![(
+            prov("inherit"),
+            table_requirements(Vec::new(), Vec::new(), Some((Vec::new(), "use workspace"))),
+        )],
+    );
+
+    assert_eq!(findings.len(), 1);
+    assert_eq!(mismatch_count_for_key(&findings, "[lints.rust]"), 1);
+}
+
 #[test]
 fn exact_nonempty_reports_missing_and_extra_tables() {
     let findings = cargo_findings_with(

packages/file-types/toml/aqc-cargo-toml-engine/tests/package_lint_tables.rs

@@ -233,6 +233,32 @@ fn reconcile_canonicalizes_components_and_targets() {
     );
 }
 
+#[test]
+fn exact_settings_reports_and_removes_unknown_toolchain_fields() {
+    let output = reconcile(
+        "[toolchain]\nchannel = \"stable\"\nfuture-setting = true\n",
+        RustToolchainTomlRequirements {
+            channel: Some(ScalarAssertion::Equals(
+                RustToolchainChannel::stable(),
+                "channel".to_owned(),
+            )),
+            exact_settings: Some("exact settings".to_owned()),
+            ..RustToolchainTomlRequirements::default()
+        },
+    );
+    let expected_bytes = first_bytes(&output);
+    let expected = String::from_utf8_lossy(&expected_bytes);
+
+    assert!(!expected.contains("future-setting"));
+    assert!(output.findings.iter().any(|finding| {
+        matches!(
+            finding,
+            Finding::Mismatch { key, message, .. }
+                if key == "toolchain.future-setting" && message == "exact settings"
+        )
+    }));
+}
+
 fn baseline_req() -> RustToolchainTomlRequirements {
     RustToolchainTomlRequirements {
         channel: Some(ScalarAssertion::Equals(

packages/file-types/toml/aqc-rust-toolchain-toml-engine/tests/behavior.rs

@@ -167,7 +167,6 @@
         "verifier": ["builtin:content"],
         "files": [
           "packages/file-types/toml/aqc-toml-engine-core/Cargo.toml",
-          "packages/file-types/toml/aqc-cargo-toml-engine/Cargo.toml",
           "packages/file-types/toml/aqc-clippy-toml-engine/Cargo.toml",
           "packages/file-types/toml/aqc-rustfmt-toml-engine/Cargo.toml",
           "packages/file-types/toml/aqc-rust-toolchain-toml-engine/Cargo.toml"
@@ -176,6 +175,13 @@
         "required": ["version = \"0.5.1\""],
         "forbidden": []
       },
+      {
+        "verifier": ["builtin:content"],
+        "files": ["packages/file-types/toml/aqc-cargo-toml-engine/Cargo.toml"],
+        "reason": "Adversarial fix: Cargo inline lint-table recognition patch release",
+        "required": ["version = \"0.5.2\""],
+        "forbidden": []
+      },
       {
         "verifier": ["builtin:content"],
         "files": ["packages/file-types/text/aqc-text-engine-core/Cargo.toml"],