Move all build steps back into file containing defs

codegen/args.go

@@ -1,10 +1,74 @@
 package codegen
 
+import (
+	"fmt"
+	"go/types"
+	"strings"
+
+	"github.com/99designs/gqlgen/codegen/templates"
+	"github.com/pkg/errors"
+	"github.com/vektah/gqlparser/ast"
+)
+
 type ArgSet struct {
 	Args     []*FieldArgument
 	FuncDecl string
 }
 
+func (b *builder) buildArg(obj *Object, arg *ast.ArgumentDefinition) (*FieldArgument, error) {
+	argDirs, err := b.getDirectives(arg.Directives)
+	if err != nil {
+		return nil, err
+	}
+	newArg := FieldArgument{
+		GQLName:       arg.Name,
+		TypeReference: b.NamedTypes.getType(arg.Type),
+		Object:        obj,
+		GoVarName:     templates.ToGoPrivate(arg.Name),
+		Directives:    argDirs,
+	}
+
+	if !newArg.TypeReference.Definition.GQLDefinition.IsInputType() {
+		return nil, errors.Errorf(
+			"cannot use %s as argument %s because %s is not a valid input type",
+			newArg.Definition.GQLDefinition.Name,
+			arg.Name,
+			newArg.TypeReference.Definition.GQLDefinition.Kind,
+		)
+	}
+
+	if arg.DefaultValue != nil {
+		newArg.Default, err = arg.DefaultValue.Value(nil)
+		if err != nil {
+			return nil, errors.Errorf("default value is not valid: %s", err.Error())
+		}
+	}
+
+	return &newArg, nil
+}
+
+func (b *builder) bindArgs(field *Field, params *types.Tuple) error {
+	var newArgs []*FieldArgument
+
+nextArg:
+	for j := 0; j < params.Len(); j++ {
+		param := params.At(j)
+		for _, oldArg := range field.Args {
+			if strings.EqualFold(oldArg.GQLName, param.Name()) {
+				oldArg.TypeReference.GoType = param.Type()
+				newArgs = append(newArgs, oldArg)
+				continue nextArg
+			}
+		}
+
+		// no matching arg found, abort
+		return fmt.Errorf("arg %s not found on method", param.Name())
+	}
+
+	field.Args = newArgs
+	return nil
+}
+
 func (a *Data) Args() map[string][]*FieldArgument {
 	ret := map[string][]*FieldArgument{}
 	for _, o := range a.Objects {