From 194a6c8df620bda3debd213f975467c4555047db Mon Sep 17 00:00:00 2001
From: Patrick Quist <partouf@gmail.com>
Date: Tue, 25 Nov 2025 00:55:45 +0100
Subject: [PATCH] Add GOCACHE support for Go compiler with writeable cache
 directory (#8283)

---
 lib/compilers/golang.ts | 52 ++++++++++++++++++++++++++++++++++++++---
 test/golang-tests.ts    | 40 +++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+), 3 deletions(-)

diff --git a/lib/compilers/golang.ts b/lib/compilers/golang.ts
index 1159f8c78..6c413b443 100644
--- a/lib/compilers/golang.ts
+++ b/lib/compilers/golang.ts
@@ -22,8 +22,11 @@
 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 // POSSIBILITY OF SUCH DAMAGE.
 
-import _ from 'underscore';
+import fs from 'node:fs/promises';
+import path from 'node:path';
 
+import _ from 'underscore';
+import type {ExecutionOptionsWithEnv} from '../../types/compilation/compilation.interfaces.js';
 import type {PreliminaryCompilerInfo} from '../../types/compiler.interfaces.js';
 import type {ParseFiltersAndOutputOptions} from '../../types/features/filters.interfaces.js';
 import type {ResultLine} from '../../types/resultline/resultline.interfaces.js';
@@ -54,6 +57,7 @@ type GoEnv = {
 
 export class GolangCompiler extends BaseCompiler {
     private readonly GOENV: GoEnv;
+    private readonly sourceCachePath?: string;
 
     static get key() {
         return 'golang';
@@ -63,11 +67,14 @@ export class GolangCompiler extends BaseCompiler {
         super(compilerInfo, env);
         const group = this.compiler.group;
 
-        const goroot = this.compilerProps<string | undefined>(
+        let goroot = this.compilerProps<string | undefined>(
             'goroot',
             this.compilerProps<string | undefined>(`group.${group}.goroot`),
         );
-        // GOARCH can be something like '386' which is read out as a number.
+        if (!goroot && compilerInfo.exe) {
+            goroot = path.dirname(path.dirname(compilerInfo.exe));
+        }
+
         const goarch = this.compilerProps<string | number | undefined>(
             'goarch',
             this.compilerProps<string | undefined>(`group.${group}.goarch`),
@@ -80,6 +87,7 @@ export class GolangCompiler extends BaseCompiler {
         this.GOENV = {};
         if (goroot) {
             this.GOENV.GOROOT = goroot;
+            this.sourceCachePath = path.join(goroot, '..', 'cache');
         }
         if (goarch) {
             this.GOENV.GOARCH = goarch.toString();
@@ -89,6 +97,44 @@ export class GolangCompiler extends BaseCompiler {
         }
     }
 
+    override async runCompiler(
+        compiler: string,
+        options: string[],
+        inputFilename: string,
+        execOptions: ExecutionOptionsWithEnv,
+        filters?: ParseFiltersAndOutputOptions,
+    ) {
+        if (!execOptions) {
+            execOptions = this.getDefaultExecOptions();
+        }
+
+        if (this.sourceCachePath) {
+            const inputDir = path.dirname(inputFilename);
+            const tempCachePath = path.join(inputDir, 'cache');
+
+            execOptions.env = {
+                ...execOptions.env,
+                GOCACHE: tempCachePath,
+            };
+
+            try {
+                await fs.mkdir(tempCachePath, {recursive: true});
+
+                try {
+                    // todo: add actual check instead of relying on exceptions
+                    await fs.access(this.sourceCachePath);
+                    await fs.cp(this.sourceCachePath, tempCachePath, {recursive: true, force: false});
+                } catch {
+                    // Source cache doesn't exist, use empty cache
+                }
+            } catch {
+                // Cache setup failed, continue without cache
+            }
+        }
+
+        return super.runCompiler(compiler, options, inputFilename, execOptions, filters);
+    }
+
     convertNewGoL(code: ResultLine[]): string {
         let prevLine: string | null = null;
         let file: string | null = null;
diff --git a/test/golang-tests.ts b/test/golang-tests.ts
index 106195c38..92bcdf21b 100644
--- a/test/golang-tests.ts
+++ b/test/golang-tests.ts
@@ -83,3 +83,43 @@ describe('GO asm tests', () => {
         await testGoAsm('test/golang/labels');
     });
 });
+
+describe('GO environment variables', () => {
+    beforeAll(() => {
+        ce = makeCompilationEnvironment({languages});
+    });
+
+    it('Derives GOROOT from compiler executable path', () => {
+        const compilerInfo = makeFakeCompilerInfo({
+            exe: '/opt/compiler-explorer/go1.20/bin/go',
+            lang: languages.go.id,
+        });
+        const compiler = new GolangCompiler(compilerInfo, ce);
+        const execOptions = compiler.getDefaultExecOptions();
+
+        expect(execOptions.env.GOROOT).toBe('/opt/compiler-explorer/go1.20');
+        // GOCACHE is not set in default exec options, it's set during runCompiler
+        expect(execOptions.env.GOCACHE).toBeUndefined();
+    });
+
+    it('Uses explicit GOROOT from properties when set', () => {
+        const compilerInfo = makeFakeCompilerInfo({
+            exe: '/opt/compiler-explorer/go1.20/bin/go',
+            lang: languages.go.id,
+            id: 'go120',
+        });
+        // Override compilerProps to return a specific GOROOT
+        const ceWithProps = makeCompilationEnvironment({
+            languages,
+            props: {
+                goroot: '/custom/goroot/path',
+            },
+        });
+        const compiler = new GolangCompiler(compilerInfo, ceWithProps);
+        const execOptions = compiler.getDefaultExecOptions();
+
+        expect(execOptions.env.GOROOT).toBe('/custom/goroot/path');
+        // GOCACHE is not set in default exec options, it's set during runCompiler
+        expect(execOptions.env.GOCACHE).toBeUndefined();
+    });
+});