Cody completions: Log multi-line completion requests and results (#52449)

Adds a flag to the event logs so we know how often multi-line
suggestions are triggered.

Logging how often they are accepted is a bit tricker and requires some
resturcturing. For now we do not know for an accepted event wether it
was a multi line or a single line completion. Will fix it up later (but
I plan to cut a release in a bit)

## Test plan

<img width="1092" alt="Screenshot 2023-05-25 at 14 14 15"
src="https://github.com/sourcegraph/sourcegraph/assets/458591/da3ed4c4-b0c2-4906-9680-b6324c483c04">


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

Author: philipp-spiess

client/cody/src/completions/index.ts

@@ -13,7 +13,6 @@ import { CompletionsDocumentProvider } from './docprovider'
 import { History } from './history'
 import { CompletionProvider, InlineCompletionProvider, ManualCompletionProvider } from './provider'
 
-const LOG_INLINE = { type: 'inline' }
 const LOG_MANUAL = { type: 'manual' }
 
 function lastNLines(text: string, n: number): string {
@@ -161,6 +160,8 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
             return []
         }
 
+        let multilineMode: null | 'block' = null
+
         // TODO(philipp-spiess): Add a better detection for start-of-block and don't require C like
         // languages.
         const multilineEnabledLanguage =
@@ -173,6 +174,7 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
             prefix.trim().at(prefix.trim().length - 1) === '{'
         ) {
             timeout = 500
+            multilineMode = 'block'
             completers.push(
                 new InlineCompletionProvider(
                     this.completionsClient,
@@ -183,7 +185,7 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
                     suffix,
                     '',
                     3,
-                    'block' // multiline
+                    multilineMode
                 )
             )
         } else if (precedingLine.trim() === '') {
@@ -241,16 +243,21 @@ export class CodyCompletionItemProvider implements vscode.InlineCompletionItemPr
             return []
         }
 
-        logEvent('CodyVSCodeExtension:completion:started', LOG_INLINE, LOG_INLINE)
+        const logParams = {
+            type: 'inline',
+            multilineMode,
+        }
+
+        logEvent('CodyVSCodeExtension:completion:started', logParams, logParams)
         const start = Date.now()
 
         const results = rankCompletions(
             (await Promise.all(completers.map(c => c.generateCompletions(abortController.signal)))).flat()
         )
 
         if (hasVisibleCompletions(results)) {
-            const params = { ...LOG_INLINE, latency: Date.now() - start, timeout }
-            logEvent('CodyVSCodeExtension:completion:suggested', params, params)
+            const logParamsWithTimings = { ...logParams, latency: Date.now() - start, timeout }
+            logEvent('CodyVSCodeExtension:completion:suggested', logParamsWithTimings, logParamsWithTimings)
             inlineCompletionsCache.add(results)
             return results.map(toInlineCompletionItem)
         }