From 2d36c62de8879e08ed945b749fe4898cb45531f2 Mon Sep 17 00:00:00 2001
From: Nicolas Peugnet <nicolas@club1.fr>
Date: Sun, 16 Mar 2025 13:48:57 +0100
Subject: [PATCH] Fix loading packages with Go modules disabled

This allows the parser to load packages even when Go modules are
disabled, and when GOPATH mode is used.
This is especially useful in Debian as we build Go packages in GOPATH
mode, and the tests are also run in this mode.
---
 v2/parser/parse.go | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/v2/parser/parse.go b/v2/parser/parse.go
index 4c1efa00..01db6b41 100644
--- a/v2/parser/parse.go
+++ b/v2/parser/parse.go
@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"go/ast"
+	"go/build"
 	"go/constant"
 	"go/token"
 	gotypes "go/types"
@@ -129,7 +130,14 @@ func (p *Parser) findPackages(baseCfg *packages.Config, patterns ...string) ([]s
 	}
 	var allErrs []error
 	for _, pkg := range pkgs {
-		results = append(results, pkg.PkgPath)
+		pkgPath := pkg.PkgPath
+		if pkgPath[0] == '_' && strings.HasPrefix(pkgPath[1:], build.Default.GOPATH) {
+			// If GOPATH mode is used, the PkgPath returned by packages.Load
+			// will be of the form "_<GOPATH>/src/<IMPORT_PATH>". We thus
+			// reslice the string to only get the <IMPORT_PATH> part.
+			pkgPath = pkg.PkgPath[len(build.Default.GOPATH)+6:]
+		}
+		results = append(results, pkgPath)
 
 		// pkg.Errors is not a slice of `error`, but concrete types.  We have
 		// to iteratively convert each one into `error`.