1 files changed, 23 insertions, 13 deletions
diff --git a/nix/buildGo/external/main.go b/nix/buildGo/external/main.go
index 50c6c85895..4402a8eb86 100644
--- a/nix/buildGo/external/main.go
+++ b/nix/buildGo/external/main.go
@@ -10,7 +10,6 @@ import (
 	"flag"
 	"fmt"
 	"go/build"
-	"io/ioutil"
 	"log"
 	"os"
 	"path"
@@ -29,13 +28,19 @@ var stdlibList string
 // Return information includes the local (relative from project root)
 // and external (none-stdlib) dependencies of this package.
 type pkg struct {
-	Name        string     `json:"name"`
-	Locator     []string   `json:"locator"`
-	Files       []string   `json:"files"`
-	SFiles      []string   `json:"sfiles"`
-	LocalDeps   [][]string `json:"localDeps"`
-	ForeignDeps []string   `json:"foreignDeps"`
-	IsCommand   bool       `json:"isCommand"`
+	Name        string       `json:"name"`
+	Locator     []string     `json:"locator"`
+	Files       []string     `json:"files"`
+	SFiles      []string     `json:"sfiles"`
+	LocalDeps   [][]string   `json:"localDeps"`
+	ForeignDeps []foreignDep `json:"foreignDeps"`
+	IsCommand   bool         `json:"isCommand"`
+}
+
+type foreignDep struct {
+	Path string `json:"path"`
+	// filename, column and line number of the import, if known
+	Position string `json:"position"`
 }
 
 // findGoDirs returns a filepath.WalkFunc that identifies all
@@ -68,8 +73,8 @@ func findGoDirs(at string) ([]string, error) {
 	}
 
 	goDirs := []string{}
-	for k, _ := range dirSet {
-		goDirs = append(goDirs, k)
+	for goDir := range dirSet {
+		goDirs = append(goDirs, goDir)
 	}
 
 	return goDirs, nil
@@ -88,7 +93,7 @@ func analysePackage(root, source, importpath string, stdlib map[string]bool) (pk
 	}
 
 	local := [][]string{}
-	foreign := []string{}
+	foreign := []foreignDep{}
 
 	for _, i := range p.Imports {
 		if stdlib[i] {
@@ -100,7 +105,12 @@ func analysePackage(root, source, importpath string, stdlib map[string]bool) (pk
 		} else if strings.HasPrefix(i, importpath+"/") {
 			local = append(local, strings.Split(strings.TrimPrefix(i, importpath+"/"), "/"))
 		} else {
-			foreign = append(foreign, i)
+			// The import positions is a map keyed on the import name.
+			// The value is a list, presumably because an import can appear
+			// multiple times in a package. Let’s just take the first one,
+			// should be enough for a good error message.
+			firstPos := p.ImportPos[i][0].String()
+			foreign = append(foreign, foreignDep{Path: i, Position: firstPos})
 		}
 	}
 
@@ -137,7 +147,7 @@ func analysePackage(root, source, importpath string, stdlib map[string]bool) (pk
 }
 
 func loadStdlibPkgs(from string) (pkgs map[string]bool, err error) {
-	f, err := ioutil.ReadFile(from)
+	f, err := os.ReadFile(from)
 	if err != nil {
 		return
 	}