feat(config): warn on unknown config keys in foundry.toml (#11816)

* feat(config): warn on unknown config keys in foundry.toml\n\n- Add Warning::UnknownKey and Display\n- Collect unknown top-level keys in active profile via WarningsProvider\n- Ignore casing-only differences (kebab/snake)\n- Add unit test for unknown key warning\n\nRefs: #10550, inspired by #10621

* Fix test, apply check for all profiles

* Fmt

---------

Co-authored-by: grandizzy <[email protected]>

Author: TropicalDog17

crates/config/src/lib.rs

@@ -6322,4 +6322,23 @@ mod tests {
             Ok(())
         });
     }
+
+    #[test]
+    fn warns_on_unknown_keys_in_profile() {
+        figment::Jail::expect_with(|jail| {
+            jail.create_file(
+                "foundry.toml",
+                r#"
+                [profile.default]
+                unknown_key_xyz = 123
+                "#,
+            )?;
+
+            let cfg = Config::load().unwrap();
+            assert!(cfg.warnings.iter().any(
+                |w| matches!(w, crate::Warning::UnknownKey { key, .. } if key == "unknown_key_xyz")
+            ));
+            Ok(())
+        });
+    }
 }

crates/config/src/providers/warnings.rs

@@ -3,6 +3,7 @@ use figment::{
     Error, Figment, Metadata, Profile, Provider,
     value::{Dict, Map, Value},
 };
+use heck::ToSnakeCase;
 use std::collections::BTreeMap;
 
 /// Generate warnings for unknown sections and deprecated keys
@@ -74,15 +75,54 @@ impl<P: Provider> WarningsProvider<P> {
             .iter()
             .filter(|(profile, _)| **profile == Config::PROFILE_SECTION)
             .map(|(_, dict)| dict);
+
         out.extend(profiles.clone().flat_map(BTreeMap::keys).filter_map(deprecated_key_warning));
         out.extend(
             profiles
+                .clone()
                 .filter_map(|dict| dict.get(self.profile.as_str().as_str()))
                 .filter_map(Value::as_dict)
                 .flat_map(BTreeMap::keys)
                 .filter_map(deprecated_key_warning),
         );
 
+        // Add warning for unknown keys within profiles (root keys only here).
+        if let Ok(default_map) = figment::providers::Serialized::defaults(&Config::default()).data()
+            && let Some(default_dict) = default_map.get(&Config::DEFAULT_PROFILE)
+        {
+            let allowed_keys: std::collections::BTreeSet<String> =
+                default_dict.keys().cloned().collect();
+            for profile_map in profiles {
+                for (profile, value) in profile_map {
+                    let Some(profile_dict) = value.as_dict() else {
+                        continue;
+                    };
+
+                    let source = self
+                        .provider
+                        .metadata()
+                        .source
+                        .map(|s| s.to_string())
+                        .unwrap_or(Config::FILE_NAME.to_string());
+                    for key in profile_dict.keys() {
+                        let is_not_deprecated =
+                            !DEPRECATIONS.iter().any(|(deprecated_key, _)| *deprecated_key == key);
+                        let is_not_allowed = !allowed_keys.contains(key)
+                            && !allowed_keys.contains(&key.to_snake_case());
+                        let is_not_reserved = key != "extends" && key != Self::WARNINGS_KEY;
+
+                        if is_not_deprecated && is_not_allowed && is_not_reserved {
+                            out.push(Warning::UnknownKey {
+                                key: key.clone(),
+                                profile: profile.clone(),
+                                source: source.clone(),
+                            });
+                        }
+                    }
+                }
+            }
+        }
+
         Ok(out)
     }
 }

crates/config/src/warning.rs

@@ -46,6 +46,15 @@ pub enum Warning {
         /// is being removed completely without replacement
         new: String,
     },
+    /// An unknown key was encountered in a profile in a TOML file
+    UnknownKey {
+        /// The unknown key name
+        key: String,
+        /// The profile where the key was found, if applicable
+        profile: String,
+        /// The config file where the key was found
+        source: String,
+    },
 }
 
 impl fmt::Display for Warning {
@@ -87,6 +96,12 @@ impl fmt::Display for Warning {
                     "Key `{old}` is being deprecated in favor of `{new}`. It will be removed in future versions."
                 )
             }
+            Self::UnknownKey { key, profile, source } => {
+                write!(
+                    f,
+                    "Found unknown `{key}` config for profile `{profile}` defined in {source}."
+                )
+            }
         }
     }
 }

crates/forge/tests/cli/config.rs

@@ -1945,3 +1945,25 @@ forgetest!(no_warnings_on_external_sections, |prj, cmd| {
 
 "#]]);
 });
+
+// <https://github.com/foundry-rs/foundry/issues/10550>
+forgetest!(config_warnings_on_unknown_keys, |prj, cmd| {
+    cmd.git_init();
+
+    let faulty_toml = r"[profile.default]
+    src = 'src'
+    out = 'out'
+    foo = 'unknown'
+
+    [profile.another]
+    src = 'src'
+    out = 'out'
+    bar = 'another_unknown'";
+
+    fs::write(prj.root().join("foundry.toml"), faulty_toml).unwrap();
+    cmd.forge_fuse().args(["config"]).assert_success().stderr_eq(str![[r#"
+Warning: Found unknown `bar` config for profile `another` defined in foundry.toml.
+Warning: Found unknown `foo` config for profile `default` defined in foundry.toml.
+
+"#]]);
+});