From 4d908753d2e7fd59d8043d5ff5d0a5833e13fa79 Mon Sep 17 00:00:00 2001
From: Li Jie <cpunion@gmail.com>
Date: Mon, 6 Jul 2026 16:59:20 +0800
Subject: [PATCH] cltest: share one go-build cache across captured runs

Every RunAndCapture created a fresh temp GOCACHE and deleted it after,
so each of the ~170 golden-dir run tests re-typechecked the entire
dependency graph from scratch. Share one per-process temp cache
instead: isolation from the developer cache is unchanged (still a
fresh temp dir per test process), and the go build cache is
content+flag keyed, so sharing across build configs is safe.

Measured on darwin/arm64 (controlled A/B, run-mode _testrt suite,
63 dirs): 157.8s -> 119.6s (-24%). Full ./cl and ./ssa suites green
with the change. The win should be larger on CI mac runners, where
the per-test cache churn hits slow disks; the mac coverage job's cl
package alone runs 37-45 minutes there.
---
 cl/cltest/cltest.go | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/cl/cltest/cltest.go b/cl/cltest/cltest.go
index 51f199bf94..c59db54e24 100644
--- a/cl/cltest/cltest.go
+++ b/cl/cltest/cltest.go
@@ -33,6 +33,7 @@ import (
 	"runtime"
 	"slices"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/goplus/gogen/packages"
@@ -313,6 +314,21 @@ func testRunAndTestFrom(t *testing.T, pkgDir, relPkg, sel string, opts runOption
 	}
 }
 
+// sharedGoCacheDir returns a per-process go-build cache reused by every
+// captured run. Isolation from the developer cache is preserved (fresh
+// temp dir per test process); sharing across tests avoids re-typechecking
+// the whole dependency graph for each of the ~170 golden dirs.
+var goCacheOnce sync.Once
+var goCacheDir string
+var goCacheErr error
+
+func sharedGoCacheDir() (string, error) {
+	goCacheOnce.Do(func() {
+		goCacheDir, goCacheErr = os.MkdirTemp("", "llgo-gocache-*")
+	})
+	return goCacheDir, goCacheErr
+}
+
 func RunAndCapture(relPkg, pkgDir string) ([]byte, error) {
 	conf := build.NewDefaultConf(build.ModeRun)
 	return RunAndCaptureWithConf(relPkg, pkgDir, conf)
@@ -376,11 +392,10 @@ func runWithConf(relPkg, pkgDir string, conf *build.Config) ([]byte, error) {
 }
 
 func doWithConf(relPkg, pkgDir string, conf *build.Config, action string) ([]byte, error) {
-	cacheDir, err := os.MkdirTemp("", "llgo-gocache-*")
+	cacheDir, err := sharedGoCacheDir()
 	if err != nil {
 		return nil, err
 	}
-	defer os.RemoveAll(cacheDir)
 	oldCache := os.Getenv("GOCACHE")
 	if err := os.Setenv("GOCACHE", cacheDir); err != nil {
 		return nil, err