Cody: Log chat prediction usage (#51474)

Adds logging to the chat prediction experimental feature.

## Test plan


https://user-images.githubusercontent.com/458591/236258186-697fcbfb-1ce8-45dd-8703-86a1e7b8dbee.mov



<!-- All pull requests REQUIRE a test plan:
https://docs.sourcegraph.com/dev/background-information/testing_principles
-->

client/cody-ui/src/Chat.tsx

@@ -23,7 +23,7 @@ interface ChatProps extends ChatClassNames {
     setFormInput: (input: string) => void
     inputHistory: string[]
     setInputHistory: (history: string[]) => void
-    onSubmit: (text: string) => void
+    onSubmit: (text: string, submitType: 'user' | 'suggestion') => void
     textAreaComponent: React.FunctionComponent<ChatUITextAreaProps>
     submitButtonComponent: React.FunctionComponent<ChatUISubmitButtonProps>
     suggestionButtonComponent?: React.FunctionComponent<ChatUISuggestionButtonProps>
@@ -138,12 +138,12 @@ export const Chat: React.FunctionComponent<ChatProps> = ({
     )
 
     const submitInput = useCallback(
-        (input: string): void => {
+        (input: string, submitType: 'user' | 'suggestion'): void => {
             if (messageInProgress) {
                 return
             }
 
-            onSubmit(input)
+            onSubmit(input, submitType)
             setSuggestions?.(undefined)
             setHistoryIndex(input.length + 1)
             setInputHistory([...inputHistory, input])
@@ -156,7 +156,7 @@ export const Chat: React.FunctionComponent<ChatProps> = ({
         if (formInput.trim() && !messageInProgress) {
             setInputRows(5)
             setFormInput('')
-            submitInput(formInput)
+            submitInput(formInput, 'user')
         }
     }, [formInput, messageInProgress, setFormInput, submitInput])
 
@@ -223,7 +223,7 @@ export const Chat: React.FunctionComponent<ChatProps> = ({
                                 <SuggestionButton
                                     key={suggestion}
                                     suggestion={suggestion}
-                                    onClick={() => submitInput(suggestion)}
+                                    onClick={() => submitInput(suggestion, 'suggestion')}
                                 />
                             ) : null
                         )}

client/cody/CHANGELOG.md

@@ -6,6 +6,8 @@ All notable changes to Sourcegraph Cody will be documented in this file.
 
 ### Added
 
+- Adds usage metrics to the experimental chat predictions feature [pull/51474](https://github.com/sourcegraph/sourcegraph/pull/51474)
+
 ### Fixed
 
 ### Changed

client/cody/src/chat/ChatViewProvider.ts

@@ -155,11 +155,11 @@ export class ChatViewProvider implements vscode.WebviewViewProvider, vscode.Disp
                 this.sendChatHistory()
                 break
             case 'submit':
-                await this.onHumanMessageSubmitted(message.text)
+                await this.onHumanMessageSubmitted(message.text, message.submitType)
                 break
             case 'edit':
                 this.transcript.removeLastInteraction()
-                await this.onHumanMessageSubmitted(message.text)
+                await this.onHumanMessageSubmitted(message.text, 'user')
                 break
             case 'executeRecipe':
                 await this.executeRecipe(message.recipe)
@@ -287,7 +287,10 @@ export class ChatViewProvider implements vscode.WebviewViewProvider, vscode.Disp
         void this.saveTranscriptToChatHistory()
     }
 
-    private async onHumanMessageSubmitted(text: string): Promise<void> {
+    private async onHumanMessageSubmitted(text: string, submitType: 'user' | 'suggestion'): Promise<void> {
+        if (submitType === 'suggestion') {
+            logEvent('CodyVSCodeExtension:chatPredictions:used')
+        }
         this.inputHistory.push(text)
 
         if (this.config.experimentalChatPredictions) {

client/cody/src/chat/protocol.ts

@@ -12,7 +12,7 @@ export type WebviewMessage =
           command: 'initialized'
       }
     | { command: 'event'; event: string; value: string }
-    | { command: 'submit'; text: string }
+    | { command: 'submit'; text: string; submitType: 'user' | 'suggestion' }
     | { command: 'executeRecipe'; recipe: string }
     | { command: 'settings'; serverEndpoint: string; accessToken: string }
     | { command: 'removeToken' }

client/cody/webviews/Chat.tsx

@@ -51,8 +51,8 @@ export const Chat: React.FunctionComponent<React.PropsWithChildren<ChatboxProps>
     setSuggestions,
 }) => {
     const onSubmit = useCallback(
-        (text: string) => {
-            vscodeAPI.postMessage({ command: 'submit', text: escapeCodyMarkdown(text) })
+        (text: string, submitType: 'user' | 'suggestion') => {
+            vscodeAPI.postMessage({ command: 'submit', text: escapeCodyMarkdown(text), submitType })
         },
         [vscodeAPI]
     )