From d8cc0c70f1200888ab4a0bcb043ea656f1e17fd9 Mon Sep 17 00:00:00 2001
From: geoknee <georgeknee@googlemail.com>
Date: Thu, 8 Oct 2026 21:27:45 +0100
Subject: [PATCH] fix: key melange cache by cargo profile

The melange cache key hashed only the lockfiles, so caches saved by
default-branch maxperf builds were restored by fast-build PR builds as an
exact hit. Nothing in a maxperf target/ is reusable under fast-build, so
PRs paid the multi-GB restore and then recompiled every crate (2002 crates
on optimism's op-stack-rust leg).

Include the cargo profile in both the key and the restore-keys prefix,
terminated with '.' so one profile's prefix never matches another's.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
---
 .github/workflows/melange-build.yaml | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/melange-build.yaml b/.github/workflows/melange-build.yaml
index 228d507..2a902d9 100644
--- a/.github/workflows/melange-build.yaml
+++ b/.github/workflows/melange-build.yaml
@@ -220,9 +220,17 @@ jobs:
           steps.cache-policy.outputs.restore == 'true' ||
           steps.cache-policy.outputs.save == 'true'
         id: cache-key
+        env:
+          CARGO_PROFILE: ${{ inputs.cargo-profile }}
         run: |
           set -euo pipefail
-          key="melange-v2-${{ inputs.stack }}-${{ inputs.arch }}"
+          # Builds under different cargo profiles share no target/ artifacts, so
+          # a cache saved by one profile is dead weight for another. The '.'
+          # terminator cannot appear in a cargo profile name, so the restore
+          # prefix for one profile never matches another it is a prefix of
+          # (release vs release-perf).
+          prefix="melange-v2-${{ inputs.stack }}-${{ inputs.arch }}-${CARGO_PROFILE:-none}."
+          key="$prefix"
           files="${{ inputs.cache-key-files }}"
           if [ -n "$files" ]; then
             IFS=',' read -ra paths <<< "$files"
@@ -238,9 +246,10 @@ jobs:
               hash_inputs+=("$path")
             done
             if [ "${#hash_inputs[@]}" -gt 0 ]; then
-              key="${key}-$(sha256sum "${hash_inputs[@]}" | sha256sum | cut -d' ' -f1)"
+              key="${key}$(sha256sum "${hash_inputs[@]}" | sha256sum | cut -d' ' -f1)"
             fi
           fi
+          echo "prefix=$prefix" >> "$GITHUB_OUTPUT"
           echo "key=$key" >> "$GITHUB_OUTPUT"
 
       - name: Restore melange cache
@@ -251,7 +260,7 @@ jobs:
           path: melange-cache
           key: ${{ steps.cache-key.outputs.key }}
           restore-keys: |
-            melange-v2-${{ inputs.stack }}-${{ inputs.arch }}-
+            ${{ steps.cache-key.outputs.prefix }}
 
       - name: Report restored cache
         if: steps.cache-policy.outputs.restore == 'true'