Accept a version string for the plugin manifest api field

Fixes #1040

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/plugin/src/manifest.rs

@@ -44,7 +44,7 @@ pub struct Manifest {
     pub main: String,
     /// The plugin API version the plugin was written for (1 when not given; panels and settings
     /// need 2, widgets 3).
-    #[serde(default = "api_version")]
+    #[serde(default = "api_version", deserialize_with = "api_from_number_or_string")]
     pub api: u32,
     #[serde(default)]
     pub permissions: Permissions,
@@ -61,6 +61,25 @@ fn api_version() -> u32 {
     1
 }
 
+/// `api` as a whole number or a version string (`"1.0.0"`, whose major part is the API version).
+fn api_from_number_or_string<'de, D: serde::Deserializer<'de>>(d: D) -> Result<u32, D::Error> {
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    enum Api {
+        Number(u32),
+        Text(String),
+    }
+    match Api::deserialize(d)? {
+        Api::Number(n) => Ok(n),
+        Api::Text(s) => s
+            .trim()
+            .split('.')
+            .next()
+            .and_then(|major| major.parse().ok())
+            .ok_or_else(|| serde::de::Error::custom(format!("invalid api version `{s}`"))),
+    }
+}
+
 /// What a plugin may do.
 #[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
 pub struct Permissions {

crates/plugin/src/tests.rs

@@ -462,3 +462,12 @@ fn bad_manifests_are_refused() {
         assert!(Manifest::parse(junk).is_err(), "accepted {}", junk.chars().take(40).collect::<String>());
     }
 }
+
+#[test]
+fn api_may_be_a_version_string() {
+    assert_eq!(manifest(json!({"api": "1.0.0"})).unwrap().api, 1);
+    assert_eq!(manifest(json!({"api": "2"})).unwrap().api, 2);
+    assert_eq!(manifest(json!({"api": 2})).unwrap().api, 2);
+    assert!(manifest(json!({"api": "4.0.0"})).is_err());
+    assert!(manifest(json!({"api": "x"})).is_err());
+}