Fix Interface Slice Getter Generation (#2332)

* Make modelgen test fail if generated doesn't build
Added returning list of interface to modelgen test schema

* Implement slice copying when returning interface slices

* Re-generate to satisfy the linter

Co-authored-by: Bill Rose <neptoess@gmail.com>

plugin/modelgen/models.go

@@ -229,7 +229,6 @@ func (m *Plugin) MutateConfig(cfg *config.Config) error {
 			return ""
 		}
 
-		getter := fmt.Sprintf("func (this %s) Get%s() %s { return ", templates.ToGo(model.Name), field.GoName, templates.CurrentImports.LookupType(field.Type))
 		_, interfaceFieldTypeIsPointer := field.Type.(*types.Pointer)
 		var structFieldTypeIsPointer bool
 		for _, f := range model.Fields {
@@ -238,15 +237,33 @@ func (m *Plugin) MutateConfig(cfg *config.Config) error {
 				break
 			}
 		}
+		goType := templates.CurrentImports.LookupType(field.Type)
+		if strings.HasPrefix(goType, "[]") {
+			getter := fmt.Sprintf("func (this %s) Get%s() %s {\n", templates.ToGo(model.Name), field.GoName, goType)
+			getter += fmt.Sprintf("\tif this.%s == nil { return nil }\n", field.GoName)
+			getter += fmt.Sprintf("\tinterfaceSlice := make(%s, 0, len(this.%s))\n", goType, field.GoName)
+			getter += fmt.Sprintf("\tfor _, concrete := range this.%s { interfaceSlice = append(interfaceSlice, ", field.GoName)
+			if interfaceFieldTypeIsPointer && !structFieldTypeIsPointer {
+				getter += "&"
+			} else if !interfaceFieldTypeIsPointer && structFieldTypeIsPointer {
+				getter += "*"
+			}
+			getter += "concrete) }\n"
+			getter += "\treturn interfaceSlice\n"
+			getter += "}"
+			return getter
+		} else {
+			getter := fmt.Sprintf("func (this %s) Get%s() %s { return ", templates.ToGo(model.Name), field.GoName, goType)
 
-		if interfaceFieldTypeIsPointer && !structFieldTypeIsPointer {
-			getter += "&"
-		} else if !interfaceFieldTypeIsPointer && structFieldTypeIsPointer {
-			getter += "*"
-		}
+			if interfaceFieldTypeIsPointer && !structFieldTypeIsPointer {
+				getter += "&"
+			} else if !interfaceFieldTypeIsPointer && structFieldTypeIsPointer {
+				getter += "*"
+			}
 
-		getter += fmt.Sprintf("this.%s }", field.GoName)
-		return getter
+			getter += fmt.Sprintf("this.%s }", field.GoName)
+			return getter
+		}
 	}
 	funcMap := template.FuncMap{
 		"getInterfaceByName": getInterfaceByName,

plugin/modelgen/models_test.go

@@ -1,10 +1,12 @@
 package modelgen
 
 import (
+	"errors"
 	"go/ast"
 	"go/parser"
 	"go/token"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -27,6 +29,7 @@ func TestModelGeneration(t *testing.T) {
 		FieldHook:  defaultFieldMutateHook,
 	}
 	require.NoError(t, p.MutateConfig(cfg))
+	require.NoError(t, goBuild(t, "./out/"))
 
 	require.True(t, cfg.Models.UserDefined("MissingTypeNotNull"))
 	require.True(t, cfg.Models.UserDefined("MissingTypeNullable"))
@@ -330,3 +333,14 @@ func parseAst(path string) (*ast.Package, error) {
 	}
 	return pkgs["out"], nil
 }
+
+func goBuild(t *testing.T, path string) error {
+	t.Helper()
+	cmd := exec.Command("go", "build", path)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return errors.New(string(out))
+	}
+
+	return nil
+}

plugin/modelgen/testdata/schema.graphql

@@ -169,3 +169,13 @@ type RenameFieldTest {
     badName: String!
     otherField: String!
 }
+
+interface ArrayOfA {
+    trickyField: [A!]!
+    trickyFieldPointer: [A]
+}
+
+type ImplArrayOfA implements ArrayOfA {
+    trickyField: [CDImplemented!]!
+    trickyFieldPointer: [CDImplemented]
+}