Revert "age-plugin: Make arguments to run_state_machine optional"

This reverts commit 480c621a40.

age-plugin/CHANGELOG.md

@@ -9,6 +9,10 @@ and this project adheres to Rust's notion of
 to 1.0.0 are beta releases.
 
 ## [Unreleased]
+### Fixed
+- `age_plugin::run_state_machine` reverts to non-optional arguments, undoing the
+  change from the previous release. The type arguments were impossible to set
+  correctly when attempting to pass `None`.
 
 ## [0.5.0] - 2024-02-04
 ### Changed

age-plugin/examples/age-plugin-unencrypted.rs

@@ -149,11 +149,7 @@ fn main() -> io::Result<()> {
     let opts = PluginOptions::parse();
 
     if let Some(state_machine) = opts.age_plugin {
-        run_state_machine(
-            &state_machine,
-            Some(|| RecipientPlugin),
-            Some(|| IdentityPlugin),
-        )
+        run_state_machine(&state_machine, || RecipientPlugin, || IdentityPlugin)
     } else {
         // A real plugin would generate a new identity here.
         print_new_identity(PLUGIN_NAME, &[], &[]);

age-plugin/src/lib.rs

@@ -145,8 +145,8 @@
 //!         // The plugin was started by an age client; run the state machine.
 //!         run_state_machine(
 //!             &state_machine,
-//!             Some(|| RecipientPlugin),
-//!             Some(|| IdentityPlugin),
+//!             || RecipientPlugin,
+//!             || IdentityPlugin,
 //!         )?;
 //!         return Ok(());
 //!     }
@@ -211,32 +211,14 @@ pub fn print_new_identity(plugin_name: &str, identity: &[u8], recipient: &[u8])
 /// argument when starting the plugin.
 pub fn run_state_machine<R: recipient::RecipientPluginV1, I: identity::IdentityPluginV1>(
     state_machine: &str,
-    recipient_v1: Option<impl FnOnce() -> R>,
-    identity_v1: Option<impl FnOnce() -> I>,
+    recipient_v1: impl FnOnce() -> R,
+    identity_v1: impl FnOnce() -> I,
 ) -> io::Result<()> {
     use age_core::plugin::{IDENTITY_V1, RECIPIENT_V1};
 
     match state_machine {
-        RECIPIENT_V1 => {
-            if let Some(plugin) = recipient_v1 {
-                recipient::run_v1(plugin())
-            } else {
-                Err(io::Error::new(
-                    io::ErrorKind::InvalidInput,
-                    "plugin doesn't support recipient-v1 state machine",
-                ))
-            }
-        }
-        IDENTITY_V1 => {
-            if let Some(plugin) = identity_v1 {
-                identity::run_v1(plugin())
-            } else {
-                Err(io::Error::new(
-                    io::ErrorKind::InvalidInput,
-                    "plugin doesn't support identity-v1 state machine",
-                ))
-            }
-        }
+        RECIPIENT_V1 => recipient::run_v1(recipient_v1()),
+        IDENTITY_V1 => identity::run_v1(identity_v1()),
         _ => Err(io::Error::new(
             io::ErrorKind::InvalidInput,
             "unknown plugin state machine",