Restore opam download cache feature

packages/setup-ocaml/src/cache.ts

@@ -1,4 +1,5 @@
 import * as crypto from "node:crypto";
+import * as os from "node:os";
 import * as path from "node:path";
 import * as cache from "@actions/cache";
 import * as core from "@actions/core";
@@ -65,6 +66,21 @@ async function composeOpamCacheKeys() {
   return { key, restoreKeys };
 }
 
+async function composeOpamDownloadCacheKeys() {
+  const ocamlCompiler = await RESOLVED_COMPILER;
+  const repositoryUrls = OPAM_REPOSITORIES.map(([_, value]) => value).join(",");
+  const plainKey = [ocamlCompiler, repositoryUrls].join(",");
+  const hash = crypto.createHash("sha256").update(plainKey).digest("hex");
+  const { runId } = github.context;
+  const key = `${CACHE_PREFIX}-setup-ocaml-opam-download-${hash}-${runId}`;
+  const restoreKeys = [
+    key,
+    `${CACHE_PREFIX}-setup-ocaml-opam-download-${hash}-`,
+    `${CACHE_PREFIX}-setup-ocaml-opam-download-`,
+  ];
+  return { key, restoreKeys };
+}
+
 function composeCygwinCachePaths() {
   const cygwinRootSymlinkPath = path.posix.join("/cygdrive", "d", "cygwin");
   const cygwinLocalPackageDirectory = path.join(
@@ -104,6 +120,16 @@ function composeOpamCachePaths() {
   return paths;
 }
 
+function composeOpamDownloadCachePaths() {
+  if (PLATFORM === "windows") {
+    const opamDownloadCachePath = path.join("D:", ".opam", "download-cache");
+    return [opamDownloadCachePath];
+  }
+  const homeDir = os.homedir();
+  const opamDownloadCachePath = path.join(homeDir, ".opam", "download-cache");
+  return [opamDownloadCachePath];
+}
+
 async function restoreCache(
   key: string,
   restoreKeys: string[],
@@ -185,6 +211,15 @@ export async function restoreOpamCaches() {
   });
 }
 
+export async function restoreOpamDownloadCache() {
+  return await core.group("Retrieve the opam download cache", async () => {
+    const { key, restoreKeys } = await composeOpamDownloadCacheKeys();
+    const paths = composeOpamDownloadCachePaths();
+    const cacheKey = await restoreCache(key, restoreKeys, paths);
+    return cacheKey;
+  });
+}
+
 export async function saveCygwinCache() {
   await core.group("Save the Cygwin cache", async () => {
     const { key } = await composeCygwinCacheKeys();
@@ -217,3 +252,11 @@ export async function saveOpamCache() {
     await saveCache(key, paths);
   });
 }
+
+export async function saveOpamDownloadCache() {
+  await core.group("Save the opam download cache", async () => {
+    const { key } = await composeOpamDownloadCacheKeys();
+    const paths = composeOpamDownloadCachePaths();
+    await saveCache(key, paths);
+  });
+}

packages/setup-ocaml/src/installer.ts

@@ -5,6 +5,7 @@ import { exec } from "@actions/exec";
 import {
   restoreDuneCache,
   restoreOpamCaches,
+  restoreOpamDownloadCache,
   saveCygwinCache,
   saveOpamCache,
 } from "./cache.js";
@@ -79,6 +80,7 @@ export async function installer() {
   } else {
     await update();
   }
+  await restoreOpamDownloadCache();
   if (DUNE_CACHE) {
     await restoreDuneCache();
     await installDune();

packages/setup-ocaml/src/post.ts

@@ -1,6 +1,6 @@
 import * as process from "node:process";
 import * as core from "@actions/core";
-import { saveDuneCache } from "./cache.js";
+import { saveDuneCache, saveOpamDownloadCache } from "./cache.js";
 import { DUNE_CACHE } from "./constants.js";
 import { trimDuneCache } from "./dune.js";
 
@@ -10,6 +10,7 @@ async function run() {
       await trimDuneCache();
       await saveDuneCache();
     }
+    await saveOpamDownloadCache();
     process.exit(0);
   } catch (error) {
     if (error instanceof Error) {