make sure colliding imports are stable

codegen/build.go

@@ -49,7 +49,7 @@ func (cfg *Config) models() (*ModelBuild, error) {
 		PackageName: cfg.ModelPackageName,
 		Models:      models,
 		Enums:       cfg.buildEnums(namedTypes),
-		Imports:     imports.imports,
+		Imports:     imports.finalize(),
 	}, nil
 }
 
@@ -80,7 +80,7 @@ func (cfg *Config) bind() (*Build, error) {
 		Objects:     objects,
 		Interfaces:  cfg.buildInterfaces(namedTypes, prog),
 		Inputs:      inputs,
-		Imports:     imports.imports,
+		Imports:     imports.finalize(),
 	}
 
 	if qr, ok := cfg.schema.EntryPoints["query"]; ok {

codegen/codegen.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"syscall"
 
@@ -136,6 +137,12 @@ func (cfg *Config) normalize() error {
 	return cfg.schema.Parse(cfg.SchemaStr)
 }
 
+var invalidPackageNameChar = regexp.MustCompile(`[^\w]`)
+
+func sanitizePackageName(pkg string) string {
+	return invalidPackageNameChar.ReplaceAllLiteralString(filepath.Base(pkg), "_")
+}
+
 func abs(path string) string {
 	absPath, err := filepath.Abs(path)
 	if err != nil {

codegen/import.go

@@ -5,6 +5,7 @@ import (
 )
 
 type Import struct {
+	Name  string
 	Alias string
 	Path  string
 }

codegen/import_build.go

@@ -1,9 +1,8 @@
 package codegen
 
 import (
+	"fmt"
 	"go/build"
-	"path/filepath"
-	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -44,12 +43,6 @@ func buildImports(types NamedTypes, destDir string) *Imports {
 	return &imports
 }
 
-var invalidPackageNameChar = regexp.MustCompile(`[^\w]`)
-
-func sanitizePackageName(pkg string) string {
-	return invalidPackageNameChar.ReplaceAllLiteralString(filepath.Base(pkg), "_")
-}
-
 func (s *Imports) add(path string) *Import {
 	if path == "" {
 		return nil
@@ -64,35 +57,40 @@ func (s *Imports) add(path string) *Import {
 		panic(err)
 	}
 
-	alias := ""
-	if !strings.HasSuffix(s.destDir, path) {
-		if pkg == nil {
-			panic(path + " was not loaded")
+	imp := &Import{
+		Name: pkg.Name,
+		Path: path,
+	}
+	s.imports = append(s.imports, imp)
+
+	return imp
+}
+
+func (s Imports) finalize() []*Import {
+	// ensure stable ordering by sorting
+	sort.Slice(s.imports, func(i, j int) bool {
+		return s.imports[i].Path > s.imports[j].Path
+	})
+
+	for _, imp := range s.imports {
+		if strings.HasSuffix(s.destDir, imp.Path) {
+			imp.Alias = ""
+			continue
 		}
+		alias := imp.Name
 
-		alias = pkg.Name
 		i := 1
-		imp := s.findByAlias(alias)
-		for imp != nil && imp.Path != path {
-			alias = pkg.Name + strconv.Itoa(i)
-			imp = s.findByAlias(alias)
+		for s.findByAlias(alias) != nil {
+			alias = imp.Name + strconv.Itoa(i)
 			i++
 			if i > 10 {
-				panic("too many collisions")
+				panic(fmt.Errorf("too many collisions, last attempt was %s", imp.Alias))
 			}
 		}
+		imp.Alias = alias
 	}
 
-	imp := &Import{
-		Alias: alias,
-		Path:  path,
-	}
-	s.imports = append(s.imports, imp)
-	sort.Slice(s.imports, func(i, j int) bool {
-		return s.imports[i].Alias > s.imports[j].Alias
-	})
-
-	return imp
+	return s.imports
 }
 
 func (s Imports) findByPath(importPath string) *Import {

codegen/import_test.go

@@ -36,3 +36,21 @@ func TestImportCollisions(t *testing.T) {
 
 	require.NoError(t, err)
 }
+
+func TestDeterministicDecollisioning(t *testing.T) {
+	a := Imports{
+		imports: []*Import{
+			{Name: "types", Path: "foobar/types"},
+			{Name: "types", Path: "bazfoo/types"},
+		},
+	}.finalize()
+
+	b := Imports{
+		imports: []*Import{
+			{Name: "types", Path: "bazfoo/types"},
+			{Name: "types", Path: "foobar/types"},
+		},
+	}.finalize()
+
+	require.EqualValues(t, a, b)
+}