move target index cache metrics to own module

this was causing dependencies to blow up
where quarto-latexmk was trying to load all execution engines

Author: gordonwoodhull

src/core/performance/metrics.ts

@@ -4,7 +4,7 @@
  * Copyright (C) 2020-2023 Posit Software, PBC
  */
 
-import { inputTargetIndexCacheMetrics } from "../../project/project-index.ts";
+import { inputTargetIndexCacheMetrics } from "../../project/target-index-cache-metrics.ts";
 import { functionTimes } from "./function-times.ts";
 import { Stats } from "./stats.ts";
 

src/project/project-index.ts

@@ -7,6 +7,7 @@
 import { dirname, isAbsolute, join, relative } from "../deno_ral/path.ts";
 
 import * as ld from "../core/lodash.ts";
+import { inputTargetIndexCacheMetrics } from "./target-index-cache-metrics.ts";
 
 import {
   InputTarget,
@@ -213,11 +214,6 @@ export function inputTargetIsEmpty(index: InputTargetIndex) {
 }
 
 const inputTargetIndexCache = new Map<string, InputTargetIndex>();
-export const inputTargetIndexCacheMetrics = {
-  hits: 0,
-  misses: 0,
-  invalidations: 0,
-};
 
 function readInputTargetIndexIfStillCurrent(projectDir: string, input: string) {
   const inputFile = join(projectDir, input);

src/project/target-index-cache-metrics.ts

@@ -0,0 +1,15 @@
+/*
+ * target-index-cache-metrics.ts
+ *
+ * Copyright (C) 2020-2023 Posit Software, PBC
+ */
+
+/**
+ * Performance metrics for the input target index cache
+ * Tracks cache efficiency for optional performance profiling
+ */
+export const inputTargetIndexCacheMetrics = {
+  hits: 0,
+  misses: 0,
+  invalidations: 0,
+};