feat: computedSpans now allow using matchingIndex (#31)

Co-authored-by: Bazyli Brzoska <[email protected]>
Co-authored-by: Cynthia Ma <[email protected]>

Author: xnanodax

src/v3/ensureMatcherFn.ts

@@ -77,3 +77,27 @@ export function convertLabelMatchersToFns<
   }
   return matchers
 }
+
+/**
+ * Helper function to ensure that the matcher is a function or a special token
+ */
+export function ensureMatcherFnOrSpecialToken<
+  SelectedRelationNameT extends keyof RelationSchemasT,
+  RelationSchemasT,
+  VariantsT extends string,
+  SpecialToken extends string,
+>(
+  spanMatcher:
+    | SpanMatch<SelectedRelationNameT, RelationSchemasT, VariantsT>
+    | SpecialToken,
+):
+  | SpanMatcherFn<SelectedRelationNameT, RelationSchemasT, VariantsT>
+  | SpecialToken
+  | undefined {
+  // Handle string types (special matchers)
+  if (typeof spanMatcher === 'string') {
+    return spanMatcher
+  }
+
+  return ensureMatcherFn(spanMatcher)
+}

src/v3/matchSpan.ts

@@ -7,6 +7,7 @@ export interface SpanMatcherTags {
   idleCheck?: boolean
   continueWithErrorStatus?: boolean
   requiredSpan?: boolean
+  matchingIndex?: number
 }
 
 /**
@@ -52,6 +53,11 @@ export interface SpanMatchDefinitionCombinator<
   isIdle?: boolean
   label?: string
   fn?: SpanMatcherFn<SelectedRelationNameT, RelationSchemasT, VariantsT>
+  /**
+   * This only has an effect on startSpan and endSpan for defining computed spans
+   * It must be defined on the top level matcher definition
+   * */
+  matchingIndex?: number
 }
 
 export type SpanMatchDefinition<
@@ -394,5 +400,11 @@ export function fromDefinition<
     matchers.push(definition.fn)
   }
 
-  return withAllConditions(...matchers)
+  const combined = withAllConditions(...matchers)
+
+  if (typeof definition.matchingIndex === 'number') {
+    combined.matchingIndex = definition.matchingIndex
+  }
+
+  return combined
 }