fix: change EventMsg enum so every variant takes a single struct (#925)

https://github.com/openai/codex/pull/922 did this for the
`SessionConfigured` enum variant, and I think it is generally helpful to
be able to work with the values as each enum variant as their own type,
so this converts the remaining variants and updates all of the
callsites.

Added a simple unit test to verify that the JSON-serialized version of
`Event` does not have any unexpected nesting.

codex-rs/tui/src/chatwidget.rs

@@ -5,10 +5,20 @@ use std::sync::mpsc::Sender;
 
 use codex_core::codex_wrapper::init_codex;
 use codex_core::config::Config;
+use codex_core::protocol::AgentMessageEvent;
+use codex_core::protocol::AgentReasoningEvent;
+use codex_core::protocol::ApplyPatchApprovalRequestEvent;
+use codex_core::protocol::ErrorEvent;
 use codex_core::protocol::Event;
 use codex_core::protocol::EventMsg;
+use codex_core::protocol::ExecApprovalRequestEvent;
+use codex_core::protocol::ExecCommandBeginEvent;
+use codex_core::protocol::ExecCommandEndEvent;
 use codex_core::protocol::InputItem;
+use codex_core::protocol::McpToolCallBeginEvent;
+use codex_core::protocol::McpToolCallEndEvent;
 use codex_core::protocol::Op;
+use codex_core::protocol::PatchApplyBeginEvent;
 use crossterm::event::KeyEvent;
 use ratatui::buffer::Buffer;
 use ratatui::layout::Constraint;
@@ -213,11 +223,11 @@ impl ChatWidget<'_> {
                     .add_session_info(&self.config, event);
                 self.request_redraw()?;
             }
-            EventMsg::AgentMessage { message } => {
+            EventMsg::AgentMessage(AgentMessageEvent { message }) => {
                 self.conversation_history.add_agent_message(message);
                 self.request_redraw()?;
             }
-            EventMsg::AgentReasoning { text } => {
+            EventMsg::AgentReasoning(AgentReasoningEvent { text }) => {
                 self.conversation_history.add_agent_reasoning(text);
                 self.request_redraw()?;
             }
@@ -229,15 +239,15 @@ impl ChatWidget<'_> {
                 self.bottom_pane.set_task_running(false)?;
                 self.request_redraw()?;
             }
-            EventMsg::Error { message } => {
+            EventMsg::Error(ErrorEvent { message }) => {
                 self.conversation_history.add_error(message);
                 self.bottom_pane.set_task_running(false)?;
             }
-            EventMsg::ExecApprovalRequest {
+            EventMsg::ExecApprovalRequest(ExecApprovalRequestEvent {
                 command,
                 cwd,
                 reason,
-            } => {
+            }) => {
                 let request = ApprovalRequest::Exec {
                     id,
                     command,
@@ -246,11 +256,11 @@ impl ChatWidget<'_> {
                 };
                 self.bottom_pane.push_approval_request(request)?;
             }
-            EventMsg::ApplyPatchApprovalRequest {
+            EventMsg::ApplyPatchApprovalRequest(ApplyPatchApprovalRequestEvent {
                 changes,
                 reason,
                 grant_root,
-            } => {
+            }) => {
                 // ------------------------------------------------------------------
                 // Before we even prompt the user for approval we surface the patch
                 // summary in the main conversation so that the dialog appears in a
@@ -276,18 +286,20 @@ impl ChatWidget<'_> {
                 self.bottom_pane.push_approval_request(request)?;
                 self.request_redraw()?;
             }
-            EventMsg::ExecCommandBegin {
-                call_id, command, ..
-            } => {
+            EventMsg::ExecCommandBegin(ExecCommandBeginEvent {
+                call_id,
+                command,
+                cwd: _,
+            }) => {
                 self.conversation_history
                     .add_active_exec_command(call_id, command);
                 self.request_redraw()?;
             }
-            EventMsg::PatchApplyBegin {
+            EventMsg::PatchApplyBegin(PatchApplyBeginEvent {
                 call_id: _,
                 auto_approved,
                 changes,
-            } => {
+            }) => {
                 // Even when a patch is auto‑approved we still display the
                 // summary so the user can follow along.
                 self.conversation_history
@@ -297,32 +309,31 @@ impl ChatWidget<'_> {
                 }
                 self.request_redraw()?;
             }
-            EventMsg::ExecCommandEnd {
+            EventMsg::ExecCommandEnd(ExecCommandEndEvent {
                 call_id,
                 exit_code,
                 stdout,
                 stderr,
-                ..
-            } => {
+            }) => {
                 self.conversation_history
                     .record_completed_exec_command(call_id, stdout, stderr, exit_code);
                 self.request_redraw()?;
             }
-            EventMsg::McpToolCallBegin {
+            EventMsg::McpToolCallBegin(McpToolCallBeginEvent {
                 call_id,
                 server,
                 tool,
                 arguments,
-            } => {
+            }) => {
                 self.conversation_history
                     .add_active_mcp_tool_call(call_id, server, tool, arguments);
                 self.request_redraw()?;
             }
-            EventMsg::McpToolCallEnd {
+            EventMsg::McpToolCallEnd(McpToolCallEndEvent {
                 call_id,
                 success,
                 result,
-            } => {
+            }) => {
                 self.conversation_history
                     .record_completed_mcp_tool_call(call_id, success, result);
                 self.request_redraw()?;