Add global flatten option to genqlient.yaml (fixes #404)

Applies @genqlient(flatten: true) to every operation and named fragment,
flattening fragment-spreads project-wide without per-query directives. It
is only applied where flattening is valid, so it is safe to enable
globally.

Author: HaraldNordgren

docs/CHANGELOG.md

@@ -28,6 +28,7 @@ Note that genqlient now requires Go 1.23 or higher, and is tested through Go 1.2
 
 ### New features:
 
+- Added a global `flatten` option to `genqlient.yaml` that applies `@genqlient(flatten: true)` to every operation and named fragment, so flattenable fragment-spreads are flattened project-wide without per-query directives (fixes #404). It is only applied where flattening is valid, so it is safe to enable globally.
 - Added `--version` flag to print version information including commit hash and build date
 
 ### Bug fixes:

docs/genqlient.yaml

@@ -94,7 +94,21 @@ client_getter: "github.com/you/yourpkg.GetClient"
 # Defaults to false.
 use_struct_references: boolean
 
-# If set, generated code will have a third return parameter of type 
+# If set, all fragment-spreads will default to having the
+# "flatten: true" flag, as if `# @genqlient(flatten: true)` were applied
+# to every operation and named fragment.  The flag is only applied where
+# it is valid (i.e. to fields whose selection is a single fragment-spread
+# of a compatible type); other fields are unaffected, so it is safe to
+# enable project-wide.  Per-node `# @genqlient(flatten: ...)` directives
+# still take precedence.
+#
+# See the flatten documentation in docs/genqlient_directive.graphql for
+# details on what flattening does.
+#
+# Defaults to false.
+flatten: boolean
+
+# If set, generated code will have a third return parameter of type
 # map[string]interface{}. This will contain the optional values
 # of the Extensions field send from Servers.
 # ref.: https://spec.graphql.org/October2021/#sec-Response-Format

generate/config.go

@@ -36,6 +36,7 @@ type Config struct {
 	OptionalGenericType string                  `yaml:"optional_generic_type"`
 	StructReferences    bool                    `yaml:"use_struct_references"`
 	Extensions          bool                    `yaml:"use_extensions"`
+	Flatten             bool                    `yaml:"flatten"`
 
 	// The directory of the config-file (relative to which all the other paths
 	// are resolved).  Set by ValidateAndFillDefaults.

generate/generate_test.go

@@ -274,6 +274,11 @@ func TestGenerateWithConfig(t *testing.T) {
 				},
 			},
 		},
+		{
+			"Flatten", "", []string{"FlattenConfig.graphql"}, &Config{
+				Flatten: true,
+			},
+		},
 	}
 
 	for _, test := range tests {

generate/genqlient_directive.go

@@ -505,7 +505,15 @@ func (g *generator) parsePrecedingComment(
 		}
 	}
 
-	if queryOptions != nil {
+	if queryOptions == nil {
+		// We are parsing the directive on the entire operation or fragment;
+		// apply any project-wide defaults from genqlient.yaml.  (Per-node
+		// options always win, since fillDefault is a no-op if already set.)
+		if g.Config != nil && g.Config.Flatten {
+			t := true
+			fillDefaultBool(&directive.Flatten, &t)
+		}
+	} else {
 		// If we are part of an operation/fragment, merge its options in.
 		directive.mergeOperationDirective(node, parentIfInputField, queryOptions)
 

generate/testdata/queries/FlattenConfig.graphql

@@ -0,0 +1,18 @@
+fragment VideoFields on Video {
+  id name url duration thumbnail { id }
+}
+
+# This query has no @genqlient(flatten: ...) directives; flattening is
+# expected to be applied automatically via the global `flatten: true`
+# config option.  The fragment-spread on `randomVideo` (which returns a
+# Video) is flattenable and should be flattened; `randomItem` mixes a
+# fragment-spread with other fields and so is left alone.
+query FlattenConfig {
+  randomVideo {
+    ...VideoFields
+  }
+  randomItem {
+    id name
+    ...VideoFields
+  }
+}