generates something mostly plausiblegit add .

generate/types.go

@@ -0,0 +1,66 @@
+package generate
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/vektah/gqlparser/ast"
+)
+
+func typeFor(operation *ast.OperationDefinition, schema *ast.Schema) string {
+	var builder strings.Builder
+
+	writeSelectionSetStruct(&builder, operation.SelectionSet, schema)
+
+	return builder.String()
+}
+
+func writeSelectionSetStruct(builder *strings.Builder, selectionSet ast.SelectionSet, schema *ast.Schema) {
+	builder.WriteString("struct {\n")
+	for _, selection := range selectionSet {
+		switch selection := selection.(type) {
+		case *ast.Field:
+			// TODO: assert it starts with uppercase (or do automatically if
+			// alias is not provided; in this case we may need json tags to
+			// avoid munging the query)
+			if selection.Alias != "" {
+				builder.WriteString(selection.Alias)
+			} else {
+				builder.WriteString(selection.Name)
+			}
+			builder.WriteRune(' ')
+
+			writeType(builder, selection.Definition.Type, selection.SelectionSet, schema)
+
+			// We don't need a json tag -- we just have GraphQL do the
+			// aliasing.
+			builder.WriteRune('\n')
+
+		case *ast.FragmentSpread, *ast.InlineFragment:
+			panic("TODO")
+		default:
+			panic(fmt.Errorf("invalid selection type: %v", selection))
+		}
+	}
+	builder.WriteString("}")
+}
+
+func writeType(builder *strings.Builder, typ *ast.Type, selectionSet ast.SelectionSet, schema *ast.Schema) {
+	if typ.Elem != nil {
+		// Type is a list.
+		builder.WriteString("[]")
+		typ = typ.Elem
+	} else if !typ.NonNull { // no need for pointer if we have a list
+		builder.WriteString("*")
+	}
+
+	if selectionSet != nil {
+		writeSelectionSetStruct(builder, selectionSet, schema)
+		return
+	}
+
+	// TODO: actually handle scalars.  or can we instead use gqlgen's
+	// converter?  they're doing mostly the same thing.  if not, crib from it:
+	// https://github.com/99designs/gqlgen/blob/master/plugin/modelgen/models.go#L113
+	builder.WriteString(strings.ToLower(typ.Name()))
+}