config: load config from module root

Also fix the configuration loading order.

configuration/configuration.go

@@ -110,27 +110,56 @@ func arePathsNotSet(cPaths []string) bool {
 func defaultConfigPaths() []string {
 	result := make([]string, 0, 4)
 
-	result = append(result, ".")
+	// First global config
 	if runtime.GOOS != windowsOs {
 		result = append(result, "/etc/gremlins")
 	}
 
+	// Then $XDG_CONFIG_HOME
 	xchLocation, _ := homedir.Expand("~/.config")
 	if x := os.Getenv(xdgConfigHomeKey); x != "" {
 		xchLocation = x
 	}
 	xchLocation = filepath.Join(xchLocation, "gremlins", "gremlins")
 	result = append(result, xchLocation)
 
+	// Then $HOME
 	homeLocation, err := homedir.Expand("~/.gremlins")
 	if err != nil {
 		return result
 	}
 	result = append(result, homeLocation)
 
+	// Then the Go module root
+	if root := findModuleRoot(); root != "" {
+		result = append(result, root)
+	}
+
+	// Finally the current folder
+	result = append(result, ".")
+
 	return result
 }
 
+func findModuleRoot() string {
+	// This function is duplicated from internal/gomodule. We should find a way
+	// to use here gomodule. The problem is the point of initialization, because
+	// configuration is initialised before gomodule.
+	path, _ := os.Getwd()
+	for {
+		if fi, err := os.Stat(filepath.Join(path, "go.mod")); err == nil && !fi.IsDir() {
+			return path
+		}
+		d := filepath.Dir(path)
+		if d == path {
+			break
+		}
+		path = d
+	}
+
+	return ""
+}
+
 var mutex sync.RWMutex
 
 // Set offers synchronised access to Viper.

configuration/configuration_test.go

@@ -17,6 +17,7 @@
 package configuration
 
 import (
+	"os"
 	"path/filepath"
 	"runtime"
 	"testing"
@@ -34,7 +35,6 @@ type envEntry struct {
 }
 
 func TestConfiguration(t *testing.T) {
-
 	testCases := []struct {
 		wantedConfig map[string]interface{}
 		name         string
@@ -130,12 +130,31 @@ func TestConfigPaths(t *testing.T) {
 	home, _ := homedir.Dir()
 
 	t.Run("it lookups in default locations", func(t *testing.T) {
+		oldDir, _ := os.Getwd()
+		_ = os.Chdir("testdata/config1")
+		defer func(dir string) {
+			_ = os.Chdir(dir)
+		}(oldDir)
+
 		var want []string
-		want = append(want, ".")
+
+		// First global
 		if runtime.GOOS != "windows" {
 			want = append(want, "/etc/gremlins")
 		}
-		want = append(want, filepath.Join(home, ".config", "gremlins", "gremlins"), filepath.Join(home, ".gremlins"))
+
+		// Then $XDG_CONFIG_HOME and $HOME
+		want = append(want,
+			filepath.Join(home, ".config", "gremlins", "gremlins"),
+			filepath.Join(home, ".gremlins"),
+		)
+
+		// Then module root
+		moduleRoot, _ := os.Getwd()
+		want = append(want, moduleRoot)
+
+		// Last current folder
+		want = append(want, ".")
 
 		got := defaultConfigPaths()
 
@@ -145,14 +164,33 @@ func TestConfigPaths(t *testing.T) {
 	})
 
 	t.Run("when XDG_CONFIG_HOME is set, it lookups in that locations", func(t *testing.T) {
+		oldDir, _ := os.Getwd()
+		_ = os.Chdir("testdata/config1")
+		defer func(dir string) {
+			_ = os.Chdir(dir)
+		}(oldDir)
+
 		customPath := filepath.Join("my", "custom", "path")
 		t.Setenv("XDG_CONFIG_HOME", customPath)
+
 		var want []string
-		want = append(want, ".")
+
+		// First global
 		if runtime.GOOS != "windows" {
 			want = append(want, "/etc/gremlins")
 		}
-		want = append(want, filepath.Join(customPath, "gremlins", "gremlins"), filepath.Join(home, ".gremlins"))
+
+		// Then $XDG_CONFIG_HOME and $HOME
+		want = append(want,
+			filepath.Join(customPath, "gremlins", "gremlins"),
+			filepath.Join(home, ".gremlins"))
+
+		// Then Go module root
+		moduleRoot, _ := os.Getwd()
+		want = append(want, moduleRoot)
+
+		// Last the current directory
+		want = append(want, ".")
 
 		got := defaultConfigPaths()
 

configuration/testdata/config1/go.mod

@@ -0,0 +1 @@
+module example.com

docs/docs/usage/configuration.md

@@ -20,9 +20,10 @@ Gremlins can be configured with a configuration file.
 The configuration file can be placed in (in order of precedence)
 
 1. `./.gremlins.yaml` (the current directory)
-2. `/etc/gremlins/gremlins.yaml`
-3. `$XDG_CONFIG_HOME/gremlins/gremlins.yaml`
-4. `$HOME/.gremlins.yaml`
+2. The module root
+3. `/etc/gremlins/.gremlins.yaml`
+4. `$XDG_CONFIG_HOME/gremlins/.gremlins.yaml`
+5. `$HOME/.gremlins.yaml`
 
 !!! hint
     `XDG_CONFIG_HOME` is usually `~/.config`.