refactor: simplify the Packages.Errors implementation (#3344)

internal/code/packages.go

@@ -231,8 +231,7 @@ func (p *Packages) ModTidy() error {
 
 // Errors returns any errors that were returned by Load, either from the call itself or any of the loaded packages.
 func (p *Packages) Errors() PkgErrors {
-	var res []error //nolint:prealloc
-	res = append(res, p.loadErrors...)
+	res := append([]error{}, p.loadErrors...)
 	for _, pkg := range p.packages {
 		for _, err := range pkg.Errors {
 			res = append(res, err)

internal/code/packages_test.go

@@ -1,10 +1,12 @@
 package code
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/tools/go/packages"
 )
 
 func TestPackages(t *testing.T) {
@@ -40,6 +42,22 @@ func TestPackages(t *testing.T) {
 	})
 }
 
+func TestPackagesErrors(t *testing.T) {
+	loadFirstErr := errors.New("first")
+	loadSecondErr := errors.New("second")
+	packageErr := packages.Error{Msg: "package"}
+	p := &Packages{
+		loadErrors: []error{loadFirstErr, loadSecondErr},
+		packages: map[string]*packages.Package{"github.com/99designs/gqlgen/internal/code/testdata/a": {
+			Errors: []packages.Error{packageErr},
+		}},
+	}
+
+	errs := p.Errors()
+
+	assert.Equal(t, PkgErrors([]error{loadFirstErr, loadSecondErr, packageErr}), errs)
+}
+
 func TestNameForPackage(t *testing.T) {
 	var p Packages