Add field aliasing (#376)

Added @genqlient(alias) directive to customize field names without
GraphQL aliases (fixes #367)

Author: clinta

docs/CHANGELOG.md

@@ -24,6 +24,8 @@ When releasing a new version:
 
 ### New features:
 
+- Added `@genqlient(alias)` directive to customize field names without requiring GraphQL aliases (fixes #367)
+
 ### Bug fixes:
 
 - fixed documentation link in `introduction.md`

docs/genqlient_directive.graphql

@@ -151,6 +151,25 @@ directive genqlient(
   # of MyField; what if we got back the other type?).
   flatten: Boolean
 
+  # If set, this field will use the provided name as the Go field name,
+  # without creating an alias in the GraphQL query.
+  #
+  # For example, given a query like
+  #  query MyQuery {
+  #    # @genqlient(alias: "MyGreatName")
+  #    myField
+  #  }
+  # genqlient will generate:
+  #  type MyQueryResponse struct {
+  #    MyGreatName <type> `json:"myField"`
+  #  }
+  #
+  # This is similar to the GraphQL alias syntax (e.g. `myGreatName: myField`),
+  # but it only affects the Go field name, not the GraphQL query. This is
+  # especially useful when working with GraphQL servers that limit the number
+  # of aliases you can use in a query.
+  alias: String
+
   # If set, this argument or field will use the given Go type instead of a
   # genqlient-generated type.
   #

generate/convert.go

@@ -918,6 +918,10 @@ func (g *generator) convertField(
 	}
 
 	goName := upperFirst(field.Alias)
+	if fieldOptions.Alias != "" {
+		goName = upperFirst(fieldOptions.Alias)
+	}
+
 	namePrefix = nextPrefix(namePrefix, field)
 
 	fieldGoType, err := g.convertType(

generate/genqlient_directive.go

@@ -18,6 +18,7 @@ type genqlientDirective struct {
 	Flatten   *bool
 	Bind      string
 	TypeName  string
+	Alias     string
 	// FieldDirectives contains the directives to be
 	// applied to specific fields via the "for" option.
 	// Map from type-name -> field-name -> directive.
@@ -52,6 +53,9 @@ func (dir *genqlientDirective) argsString() string {
 	if dir.TypeName != "" {
 		parts = append(parts, fmt.Sprintf("typename: %v", dir.TypeName))
 	}
+	if dir.Alias != "" {
+		parts = append(parts, fmt.Sprintf("alias: %v", dir.Alias))
+	}
 	return strings.Join(parts, ", ")
 }
 
@@ -170,6 +174,8 @@ func (dir *genqlientDirective) add(graphQLDirective *ast.Directive, pos *ast.Pos
 			err = setString("bind", &dir.Bind, arg.Value, pos)
 		case "typename":
 			err = setString("typename", &dir.TypeName, arg.Value, pos)
+		case "alias":
+			err = setString("alias", &dir.Alias, arg.Value, pos)
 		case "for":
 			// handled above
 		default:
@@ -441,6 +447,7 @@ func (dir *genqlientDirective) mergeOperationDirective(
 	// typename isn't settable on the operation (when set there it replies to
 	// the response-type).
 	fillDefaultString(&dir.TypeName, forField.TypeName)
+	fillDefaultString(&dir.Alias, forField.Alias, operationDirective.Alias)
 }
 
 // parsePrecedingComment looks at the comment right before this node, and

generate/testdata/queries/AliasDirective.graphql

@@ -0,0 +1,9 @@
+query AliasDirective {
+  # @genqlient(alias: "MyUser")
+  user {
+    # @genqlient(alias: "UserID")
+    id
+    # @genqlient(alias: "UserName")
+    name
+  }
+}

generate/testdata/snapshots/TestGenerate-AliasDirective.graphql-AliasDirective.graphql.go

@@ -0,0 +1,9 @@
+{
+  "operations": [
+    {
+      "operationName": "AliasDirective",
+      "query": "\nquery AliasDirective {\n\tuser {\n\t\tid\n\t\tname\n\t}\n}\n",
+      "sourceLocation": "testdata/queries/AliasDirective.graphql"
+    }
+  ]
+}