From af6c167d5db0f8285b4f464372fdfb5b0dc2537a Mon Sep 17 00:00:00 2001
From: Jonathan Kelley <jkelleyrtp@gmail.com>
Date: Tue, 28 Jan 2025 20:59:32 -0800
Subject: [PATCH] restore from secondary branch

---
 action.yml     |  4 ++++
 src/config.ts  | 23 ++++++++++++++++-------
 src/restore.ts | 16 ++++++++++------
 3 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/action.yml b/action.yml
index 0f1b024..36b03c5 100644
--- a/action.yml
+++ b/action.yml
@@ -52,6 +52,10 @@ inputs:
     description: "Determines whether to cache incremental builds - speeding up builds for more disk usage. Defaults to false."
     required: false
     default: "false"
+  incremental-key:
+    description: "The key to use for incremental builds. Used on a per-branch basis"
+    required: false
+    default: ${{ github.ref }}
 outputs:
   cache-hit:
     description: "A boolean value that indicates an exact match was found."
diff --git a/src/config.ts b/src/config.ts
index ecae9fb..062e95e 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -21,8 +21,16 @@ const HASH_LENGTH = 8;
 export class CacheConfig {
   /** All the paths we want to cache */
   public cachePaths: Array<string> = [];
+
+  /** All the paths we want to cache for incremental builds */
+  public incrementalPaths: Array<string> = [];
+
   /** The primary cache key */
   public cacheKey = "";
+
+  /** The primary cache key for incremental builds */
+  public incrementalKey = "";
+
   /**
    *  The secondary (restore) key that only contains the prefix and environment
    *  This should be used if the primary cacheKey is not available - IE pulling from main on a branch
@@ -255,15 +263,16 @@ export class CacheConfig {
     keyFiles.push(...parsedKeyFiles);
     self.keyFiles = sort_and_uniq(keyFiles);
 
-    // todo(jon): make sure we differentiate incrementals on different branches
-    // we can use just a single cache per incremental branch
-    if (self.incremental) {
-      key += `-incremental`;
-    }
-
     key += `-${lockHash}`;
     self.cacheKey = key;
 
+    if (self.incremental) {
+      // wire the incremental key to be just for this branch
+      const branchName = core.getInput("incremental-key") || "-shared";
+      const incrementalKey = key + `-incremental` + branchName;
+      self.incrementalKey = incrementalKey;
+    }
+
     self.cachePaths = [path.join(CARGO_HOME, "registry"), path.join(CARGO_HOME, "git")];
     if (self.cacheBin) {
       self.cachePaths = [
@@ -286,7 +295,7 @@ export class CacheConfig {
     if (self.incremental) {
       if (cacheTargets === "true") {
         for (const target of self.workspaces.map((ws) => ws.target)) {
-          self.cachePaths.push(path.join(target, "incremental"));
+          self.incrementalPaths.push(path.join(target, "incremental"));
         }
       }
     }
diff --git a/src/restore.ts b/src/restore.ts
index f592d26..c459ca5 100644
--- a/src/restore.ts
+++ b/src/restore.ts
@@ -39,20 +39,24 @@ async function run() {
 
     core.info(`... ${lookupOnly ? "Checking" : "Restoring"} cache ...`);
     const key = config.cacheKey;
+
     // Pass a copy of cachePaths to avoid mutating the original array as reported by:
     // https://github.com/actions/toolkit/pull/1378
     // TODO: remove this once the underlying bug is fixed.
-    const restoreKey = await cacheProvider.cache.restoreCache(config.cachePaths.slice(), key, [config.restoreKey], {
-      lookupOnly,
-    });
+    const restoreKey = await cacheProvider.cache.restoreCache(config.cachePaths.slice(), key, [config.restoreKey], { lookupOnly });
+
     if (restoreKey) {
       const match = restoreKey === key;
       core.info(`${lookupOnly ? "Found" : "Restored from"} cache key "${restoreKey}" full match: ${match}.`);
 
       if (config.incremental) {
-        core.debug("restoring incremental builds");
-        for (const workspace of config.workspaces) {
-          await restoreIncremental(workspace.target);
+        const incrementalKey = await cacheProvider.cache.restoreCache(config.incrementalPaths.slice(), config.incrementalKey, [config.restoreKey], { lookupOnly });
+        core.debug(`restoring incremental builds from ${incrementalKey}`);
+
+        if (incrementalKey) {
+          for (const workspace of config.workspaces) {
+            await restoreIncremental(workspace.target);
+          }
         }
       }