Cache runtime results

Author: nojaf

scripts/find-runtime.ts

@@ -19,9 +19,9 @@ Examples:
 
 const project = args[args.length - 1];
 
-import { findRuntime } from "../server/src/find-runtime.ts";
+import { findRescriptRuntimesInProject } from "../server/src/find-runtime.ts";
 
-const runtimes = await findRuntime(project);
+const runtimes = await findRescriptRuntimesInProject(project);
 
 console.log("Found @rescript/runtime directories:", runtimes);
 

server/src/bsc-args/rewatch.ts

@@ -7,7 +7,7 @@ import {
   IncrementallyCompiledFileInfo,
 } from "../incrementalCompilation";
 import type { projectFiles } from "../projectFiles";
-import { findRuntime } from "../find-runtime";
+import { findRescriptRuntimesInProject } from "../find-runtime";
 
 export type RewatchCompilerArgs = {
   compiler_args: Array<string>;
@@ -93,8 +93,9 @@ export async function getRewatchBscArgs(
     // TODO: We should check a potential configured value
     // Users should be able to provide this themselves if they like.
 
-	// TODO: We should also cache this value if we found it.
-    const rescriptRuntimes = await findRuntime(entry.project.workspaceRootPath);
+    const rescriptRuntimes = await findRescriptRuntimesInProject(
+      entry.project.workspaceRootPath,
+    );
 
     if (debug()) {
       if (rescriptRuntimes.length === 0) {

server/src/find-runtime.ts

@@ -1,5 +1,5 @@
 import { readdir, stat as statAsync } from "fs/promises";
-import { join } from "path";
+import { join, resolve } from "path";
 
 // Efficient parallel folder traversal to find node_modules directories
 async function findNodeModulesDirs(
@@ -88,7 +88,7 @@ async function findDenoRescriptRuntime(nodeModulesPath: string) {
   return results;
 }
 
-export async function findRuntime(project: string) {
+async function findRuntimePath(project: string) {
   // Find all node_modules directories using efficient traversal
   const node_modules = await findNodeModulesDirs(project);
 
@@ -117,5 +117,24 @@ export async function findRuntime(project: string) {
     }),
   ).then((results) => results.flatMap((x) => x));
 
-  return rescriptRuntimeDirs;
+  return rescriptRuntimeDirs.map((runtime) => resolve(runtime));
 }
+
+function findRuntimeCached() {
+  const cache = new Map<string, string[]>();
+  return async (project: string) => {
+    if (cache.has(project)) {
+      return cache.get(project)!;
+    }
+    const runtimes = await findRuntimePath(project);
+    cache.set(project, runtimes);
+    return runtimes;
+  };
+}
+
+/**
+ * Find all installed @rescript/runtime directories in the given project path.
+ * In a perfect world, there should be exactly one.
+ * This function is cached per project path.
+ */
+export const findRescriptRuntimesInProject = findRuntimeCached();