feat(generation): allow awsRegion to be specified by callers in Metadata

Problem: `awsRegion` is a base metric and does not allow for callers to add it to their metadata when using `record()`. However, this field is often known best by the caller and not the telemetry guessing algorithm.

Solution: Update type generation to allow this base metric to be specified in metadata.

Author: hayemaxi

telemetry/vscode/src/generate.ts

@@ -122,6 +122,10 @@ function getTypeOrThrow(types: MetadataType[] = [], name: string) {
 
 const baseName = 'MetricBase'
 
+/**
+ * Fields set automatically by the telemetry client (thus application code
+ * normally shouldn't set these because the value will be overridden).
+ */
 const commonMetadata = [
   'awsAccount',
   'awsRegion',
@@ -132,7 +136,13 @@ const commonMetadata = [
   'requestId',
   'requestServiceType',
   'result',
-]
+] as const
+
+/** 
+ * These fields will also be set by the telemetry client, but the caller might
+ * know better, so they won't be overridden if specified in `.record()` calls.
+ */
+const optionalMetadata: typeof commonMetadata[number][] = ['awsRegion']
 
 const passive: PropertySignatureStructure = {
     isReadonly: true,
@@ -183,7 +193,7 @@ const header = `
 `.trimStart()
 
 function getMetricMetadata(metric: Metric) {
-    return metric.metadata?.filter(m => !commonMetadata.includes(m.type)) ?? []
+    return metric.metadata?.filter(m => !commonMetadata.includes(m.type as typeof commonMetadata[number])) ?? []
 }
 
 function generateMetadataProperty(metadata: MetricMetadataType): PropertySignatureStructure {
@@ -351,7 +361,7 @@ function generateFile(telemetryJson: MetricDefinitionRoot, dest: string) {
         isExported: true,
         name: 'Metadata',
         typeParameters: [`T extends ${baseName}`],
-        type: `Partial<Omit<T, keyof ${baseName}>>`,
+        type: `Partial<Omit<T, keyof ${baseName}> | Partial<Pick<${baseName}, ${optionalMetadata.map(v => `'${v}'`).join(' | ')}>>>`,
         kind: StructureKind.TypeAlias,
     }
 

telemetry/vscode/test/resources/generatorOutput.ts

@@ -114,7 +114,7 @@ export const definitions: Record<string, MetricDefinition> = {
     passive_passive: { unit: 'None', passive: true, requiredMetadata: [] },
 }
 
-export type Metadata<T extends MetricBase> = Partial<Omit<T, keyof MetricBase>>
+export type Metadata<T extends MetricBase> = Partial<Omit<T, keyof MetricBase> | Partial<Pick<MetricBase, 'awsRegion'>>>
 
 export interface Metric<T extends MetricBase = MetricBase> {
     readonly name: string

telemetry/vscode/test/resources/generatorOverrideOutput.ts

@@ -85,7 +85,7 @@ export const definitions: Record<string, MetricDefinition> = {
     metadata_hasResult: { unit: 'None', passive: false, requiredMetadata: [] },
 }
 
-export type Metadata<T extends MetricBase> = Partial<Omit<T, keyof MetricBase>>
+export type Metadata<T extends MetricBase> = Partial<Omit<T, keyof MetricBase> | Partial<Pick<MetricBase, 'awsRegion'>>>
 
 export interface Metric<T extends MetricBase = MetricBase> {
     readonly name: string