Walk parent directories to find config file (#141)

Code is mostly borrowed from [gqlgen](https://github.com/99designs/gqlgen).

The idea here is that I want to be able to store `genqlient.yaml` at the top-level, but my client code lives down in `graph/client/`. I put the `//go:generate` line in `graph/client/client.go`.

docs/genqlient.yaml

@@ -1,6 +1,8 @@
 # genqlient.yaml is genqlient's configuration file.  This genqlient.yaml is an
 # example; use `go run github.com/Khan/genqlient --init` to generate a simple
-# starting point.
+# starting point.  By default, genqlient looks for the configuration file
+# named [.]genqlient.y[a]ml in the current directory or any ancestor; or the
+# filename may be given as an argument.
 
 # The filename with the GraphQL schema (in SDL format), relative to
 # genqlient.yaml.

generate/config.go

@@ -10,6 +10,8 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
+var cfgFilenames = []string{".genqlient.yml", ".genqlient.yaml", "genqlient.yml", "genqlient.yaml"}
+
 // Config represents genqlient's configuration, generally read from
 // genqlient.yaml.
 //
@@ -109,6 +111,17 @@ func ReadAndValidateConfig(filename string) (*Config, error) {
 	return &config, nil
 }
 
+// ReadAndValidateConfigFromDefaultLocations looks for a config file in the
+// current directory, and all parent directories walking up the tree. The
+// closest config file will be returned.
+func ReadAndValidateConfigFromDefaultLocations() (*Config, error) {
+	cfgFile, err := findCfg()
+	if err != nil {
+		return nil, err
+	}
+	return ReadAndValidateConfig(cfgFile)
+}
+
 func initConfig(filename string) error {
 	// TODO(benkraft): Embed this config file into the binary, see
 	// https://github.com/Khan/genqlient/issues/9.
@@ -126,3 +139,35 @@ func initConfig(filename string) error {
 	}
 	return nil
 }
+
+// findCfg searches for the config file in this directory and all parents up the tree
+// looking for the closest match
+func findCfg() (string, error) {
+	dir, err := os.Getwd()
+	if err != nil {
+		return "", errorf(nil, "unable to get working dir to findCfg: %v", err)
+	}
+
+	cfg := findCfgInDir(dir)
+
+	for cfg == "" && dir != filepath.Dir(dir) {
+		dir = filepath.Dir(dir)
+		cfg = findCfgInDir(dir)
+	}
+
+	if cfg == "" {
+		return "", os.ErrNotExist
+	}
+
+	return cfg, nil
+}
+
+func findCfgInDir(dir string) string {
+	for _, cfgName := range cfgFilenames {
+		path := filepath.Join(dir, cfgName)
+		if _, err := os.Stat(path); err == nil {
+			return path
+		}
+	}
+	return ""
+}

generate/config_test.go

@@ -0,0 +1,90 @@
+package generate
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFindCfg(t *testing.T) {
+	cwd, err := os.Getwd()
+	require.NoError(t, err)
+
+	cases := map[string]struct {
+		startDir    string
+		expectedCfg string
+		expectedErr error
+	}{
+		"yaml in parent directory": {
+			startDir:    cwd + "/testdata/find-config/parent/child",
+			expectedCfg: cwd + "/testdata/find-config/parent/genqlient.yaml",
+		},
+		"yaml in current directory": {
+			startDir:    cwd + "/testdata/find-config/current",
+			expectedCfg: cwd + "/testdata/find-config/current/genqlient.yaml",
+		},
+		"no yaml": {
+			startDir:    cwd + "/testdata/find-config/none/child",
+			expectedErr: os.ErrNotExist,
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			defer func() {
+				require.NoError(t, os.Chdir(cwd), "Test cleanup failed")
+			}()
+
+			err = os.Chdir(tc.startDir)
+			require.NoError(t, err)
+
+			path, err := findCfg()
+			assert.Equal(t, tc.expectedCfg, path)
+			assert.Equal(t, tc.expectedErr, err)
+		})
+	}
+}
+
+func TestFindCfgInDir(t *testing.T) {
+	cwd, err := os.Getwd()
+	require.NoError(t, err)
+
+	cases := map[string]struct {
+		startDir string
+		found    bool
+	}{
+		"yaml": {
+			startDir: cwd + "/testdata/find-config/filenames/yaml",
+			found:    true,
+		},
+		"yml": {
+			startDir: cwd + "/testdata/find-config/filenames/yml",
+			found:    true,
+		},
+		".yaml": {
+			startDir: cwd + "/testdata/find-config/filenames/dotyaml",
+			found:    true,
+		},
+		".yml": {
+			startDir: cwd + "/testdata/find-config/filenames/dotyml",
+			found:    true,
+		},
+		"none": {
+			startDir: cwd + "/testdata/find-config/filenames/none",
+			found:    false,
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			path := findCfgInDir(tc.startDir)
+			if tc.found {
+				assert.NotEmpty(t, path)
+			} else {
+				assert.Empty(t, path)
+			}
+		})
+	}
+}

generate/main.go

@@ -14,9 +14,18 @@ import (
 )
 
 func readConfigGenerateAndWrite(configFilename string) error {
-	config, err := ReadAndValidateConfig(configFilename)
-	if err != nil {
-		return err
+	var config *Config
+	var err error
+	if configFilename != "" {
+		config, err = ReadAndValidateConfig(configFilename)
+		if err != nil {
+			return err
+		}
+	} else {
+		config, err = ReadAndValidateConfigFromDefaultLocations()
+		if err != nil {
+			return err
+		}
 	}
 
 	generated, err := Generate(config)
@@ -42,7 +51,7 @@ func readConfigGenerateAndWrite(configFilename string) error {
 }
 
 type cliArgs struct {
-	ConfigFilename string `arg:"positional" placeholder:"CONFIG" default:"genqlient.yaml" help:"path to genqlient configuration (default genqlient.yaml)"`
+	ConfigFilename string `arg:"positional" placeholder:"CONFIG" default:"" help:"path to genqlient configuration (default: genqlient.yaml in current or any parent directory)"`
 	Init           bool   `arg:"--init" help:"write out and use a default config file"`
 }
 
@@ -67,7 +76,12 @@ func Main() {
 	var args cliArgs
 	arg.MustParse(&args)
 	if args.Init {
-		err := initConfig(args.ConfigFilename)
+		filename := args.ConfigFilename
+		if filename == "" {
+			filename = "genqlient.yaml"
+		}
+
+		err := initConfig(filename)
 		exitIfError(err)
 	}
 	err := readConfigGenerateAndWrite(args.ConfigFilename)

generate/testdata/find-config/current/genqlient.yaml

@@ -0,0 +1,6 @@
+# Default genqlient config; for full documentation see:
+# https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+schema: schema.graphql
+operations:
+- genqlient.graphql
+generated: generated.go

generate/testdata/find-config/filenames/dotyaml/.genqlient.yaml

@@ -0,0 +1,6 @@
+# Default genqlient config; for full documentation see:
+# https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+schema: schema.graphql
+operations:
+- genqlient.graphql
+generated: generated.go

generate/testdata/find-config/filenames/dotyml/.genqlient.yml

@@ -0,0 +1,6 @@
+# Default genqlient config; for full documentation see:
+# https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+schema: schema.graphql
+operations:
+- genqlient.graphql
+generated: generated.go

generate/testdata/find-config/filenames/yaml/genqlient.yaml

@@ -0,0 +1,6 @@
+# Default genqlient config; for full documentation see:
+# https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+schema: schema.graphql
+operations:
+- genqlient.graphql
+generated: generated.go

generate/testdata/find-config/filenames/yml/genqlient.yml

@@ -0,0 +1,6 @@
+# Default genqlient config; for full documentation see:
+# https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+schema: schema.graphql
+operations:
+- genqlient.graphql
+generated: generated.go

generate/testdata/find-config/parent/genqlient.yaml

@@ -0,0 +1,6 @@
+# Default genqlient config; for full documentation see:
+# https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
+schema: schema.graphql
+operations:
+- genqlient.graphql
+generated: generated.go