refactor: derive GooseMode string conversions with strum (#7706)

Signed-off-by: Adrian Cole <adrian@tetrate.io>

crates/goose/Cargo.toml

@@ -66,6 +66,7 @@ keyring = { version = "3.6.2", features = [
     "vendored",
 ] }
 serde_yaml = { workspace = true }
+strum = { workspace = true }
 once_cell = { workspace = true }
 etcetera = { workspace = true }
 rand = { workspace = true }

crates/goose/src/config/goose_mode.rs

@@ -1,26 +1,24 @@
-use std::str::FromStr;
-
 use serde::{Deserialize, Serialize};
+use strum::{Display, EnumString, IntoStaticStr, VariantNames};
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+#[derive(
+    Copy,
+    Clone,
+    Debug,
+    Eq,
+    PartialEq,
+    Serialize,
+    Deserialize,
+    Display,
+    EnumString,
+    IntoStaticStr,
+    VariantNames,
+)]
 #[serde(rename_all = "snake_case")]
+#[strum(serialize_all = "snake_case")]
 pub enum GooseMode {
     Auto,
     Approve,
     SmartApprove,
     Chat,
 }
-
-impl FromStr for GooseMode {
-    type Err = String;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "auto" => Ok(GooseMode::Auto),
-            "approve" => Ok(GooseMode::Approve),
-            "smart_approve" => Ok(GooseMode::SmartApprove),
-            "chat" => Ok(GooseMode::Chat),
-            _ => Err(format!("invalid mode: {}", s)),
-        }
-    }
-}

crates/goose/tests/providers.rs

@@ -424,14 +424,8 @@ impl ProviderTester {
         message: &str,
         label: &str,
     ) -> Result<()> {
-        let mode_str = match mode {
-            GooseMode::Approve => "approve",
-            GooseMode::SmartApprove => "smart_approve",
-            GooseMode::Auto => "auto",
-            GooseMode::Chat => "chat",
-        };
         // Guard must live through agent.reply() — providers read GOOSE_MODE at spawn time.
-        let _guard = env_lock::lock_env([("GOOSE_MODE", Some(mode_str))]);
+        let _guard = env_lock::lock_env([("GOOSE_MODE", Some(<&str>::from(mode)))]);
         let provider = if self.is_cli_provider {
             create_with_named_model(
                 &self.name.to_lowercase(),