Add new package bindings option (#169)

Add new package bindings option

This commit adds list of packages for which genqlient should automatically
generate bindings; it's equivalent to adding all the exported types in the
package to `bindings` explicitly. This can be useful when you're both a client
and a server of the same schema and want to share types. We don't recommend
doing things that way, but the feature isn't too invasive and may be useful for
other purposes.

Co-authored-by: Ben Kraft <[email protected]>

generate/config.go

@@ -2,10 +2,12 @@ package generate
 
 import (
 	_ "embed"
+	"fmt"
 	"go/token"
 	"os"
 	"path/filepath"
 
+	"golang.org/x/tools/go/packages"
 	"gopkg.in/yaml.v2"
 )
 
@@ -26,6 +28,7 @@ type Config struct {
 	ContextType      string                  `yaml:"context_type"`
 	ClientGetter     string                  `yaml:"client_getter"`
 	Bindings         map[string]*TypeBinding `yaml:"bindings"`
+	PackageBindings  []*PackageBinding       `yaml:"package_bindings"`
 	Optional         string                  `yaml:"optional"`
 	StructReferences bool                    `yaml:"use_struct_references"`
 	Extensions       bool                    `yaml:"use_extensions"`
@@ -52,6 +55,13 @@ type TypeBinding struct {
 	Unmarshaler       string `yaml:"unmarshaler"`
 }
 
+// A PackageBinding represents a Go package for which genqlient will
+// automatically generate TypeBindings, and is documented further at:
+// https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+type PackageBinding struct {
+	Package string `yaml:"package"`
+}
+
 // pathJoin is like filepath.Join but 1) it only takes two argsuments,
 // and b) if the second argument is an absolute path the first argument
 // is ignored (similar to how python's os.path.join() works).
@@ -98,6 +108,42 @@ func (c *Config) ValidateAndFillDefaults(baseDir string) error {
 		c.Package = base
 	}
 
+	if len(c.PackageBindings) > 0 {
+		for _, binding := range c.PackageBindings {
+			mode := packages.NeedImports | packages.NeedTypes | packages.NeedTypesSizes
+			pkgs, err := packages.Load(&packages.Config{
+				Mode: mode,
+			}, binding.Package)
+			if err != nil {
+				return err
+			}
+
+			if c.Bindings == nil {
+				c.Bindings = map[string]*TypeBinding{}
+			}
+
+			for _, pkg := range pkgs {
+				p := pkg.Types
+				if p == nil || p.Scope() == nil {
+					return errorf(nil, "unable to bind package %s: no types found", binding.Package)
+				}
+
+				for _, typ := range p.Scope().Names() {
+					if token.IsExported(typ) {
+						// Check if type is manual bindings
+						_, exist := c.Bindings[typ]
+						if !exist {
+							pathType := fmt.Sprintf("%s.%s", p.Path(), typ)
+							c.Bindings[typ] = &TypeBinding{
+								Type: pathType,
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
 	return nil
 }