ci: ensure "go fmt" formatting, use "any" instead of "interface{}" (#150)

Adds a check in CI that `go fmt ./...` doesn't change anything, and that
`any` is used instead of `interface{}`.

(Lifted entirely [from
Pebble](https://github.com/canonical/pebble/blob/7e8e6bf44d386e1fd6eb478e09c2722a8bd1b22a/.github/workflows/tests.yml#L46-L62)).

To satisfy the new check, also contains a `go fmt ./...` run, which
cleans up some whitespace in client_test.go.

---------

Co-authored-by: Ben Hoyt <ben.hoyt@canonical.com>

Author: tonyandrewmeyer

.github/workflows/push.yaml

@@ -15,6 +15,27 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  format:
+    name: Format check
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v6
+
+    - name: Set up Go
+      uses: actions/setup-go@v6
+      with:
+        go-version-file: 'go.mod'
+
+    - name: Ensure no formatting changes
+      run: |
+        go fmt ./...
+        git diff --exit-code
+
+    - name: Ensure no use of empty interface (should be any)
+      run: |
+        ! egrep -R --exclude-dir .git 'interface\{\}'
+
   binaries:
     name: Build concierge
     runs-on: ubuntu-latest

internal/config/util.go

@@ -2,7 +2,7 @@ package config
 
 // MergeMaps takes two maps and returns a combined map, where KV pairs in the second map arg
 // take precedence over the first.
-func MergeMaps[K string, V interface{}](m1 map[K]V, m2 map[K]V) map[K]V {
+func MergeMaps[K string, V any](m1 map[K]V, m2 map[K]V) map[K]V {
 	combinedMap := map[K]V{}
 	for k := range m1 {
 		combinedMap[k] = m1[k]

internal/juju/juju.go

@@ -126,7 +126,7 @@ func (j *JujuHandler) install() error {
 // writeCredentials iterates over any provided cloud credentials and authors Juju's
 // credentials.yaml
 func (j *JujuHandler) writeCredentials() error {
-	credentials := map[string]interface{}{"credentials": map[string]interface{}{}}
+	credentials := map[string]any{"credentials": map[string]any{}}
 	addedCredentials := false
 
 	// Iterate over the providers
@@ -137,8 +137,8 @@ func (j *JujuHandler) writeCredentials() error {
 		}
 
 		// Set the credentials for the provider, under the credential name "concierge".
-		credentials["credentials"] = map[string]interface{}{
-			p.CloudName(): map[string]interface{}{
+		credentials["credentials"] = map[string]any{
+			p.CloudName(): map[string]any{
 				"concierge": p.Credentials(),
 			},
 		}

internal/providers/google.go

@@ -20,7 +20,7 @@ func NewGoogle(system system.Worker, config *config.Config) *Google {
 		system:               system,
 		bootstrap:            config.Providers.Google.Bootstrap,
 		credentialsFile:      credentialsFile,
-		credentials:          map[string]interface{}{},
+		credentials:          map[string]any{},
 		modelDefaults:        config.Providers.Google.ModelDefaults,
 		bootstrapConstraints: config.Providers.Google.BootstrapConstraints,
 	}
@@ -31,7 +31,7 @@ type Google struct {
 	bootstrap            bool
 	system               system.Worker
 	credentialsFile      string
-	credentials          map[string]interface{}
+	credentials          map[string]any
 	modelDefaults        map[string]string
 	bootstrapConstraints map[string]string
 }
@@ -45,7 +45,7 @@ func (l *Google) Prepare() error {
 		return fmt.Errorf("failed to read credentials file: %w", err)
 	}
 
-	credentials := make(map[string]interface{})
+	credentials := make(map[string]any)
 
 	err = yaml.Unmarshal(contents, &credentials)
 	if err != nil {
@@ -71,7 +71,7 @@ func (l *Google) CloudName() string { return "google" }
 func (l *Google) GroupName() string { return "" }
 
 // Credentials reports the section of Juju's credentials.yaml for the provider.
-func (l *Google) Credentials() map[string]interface{} { return l.credentials }
+func (l *Google) Credentials() map[string]any { return l.credentials }
 
 // ModelDefaults reports the Juju model-defaults specific to the provider.
 func (l *Google) ModelDefaults() map[string]string { return l.modelDefaults }

internal/providers/google_test.go

@@ -30,23 +30,23 @@ func TestNewGoogle(t *testing.T) {
 			config: noOverrides,
 			expected: &Google{
 				system:      system,
-				credentials: map[string]interface{}{},
+				credentials: map[string]any{},
 			},
 		},
 		{
 			config: credsInConfig,
 			expected: &Google{
 				system:          system,
 				credentialsFile: "/home/ubuntu/credentials.yaml",
-				credentials:     map[string]interface{}{},
+				credentials:     map[string]any{},
 			},
 		},
 		{
 			config: overrides,
 			expected: &Google{
 				system:          system,
 				credentialsFile: "/home/ubuntu/alternate-credentials.yaml",
-				credentials:     map[string]interface{}{},
+				credentials:     map[string]any{},
 			},
 		},
 	}
@@ -92,7 +92,7 @@ private-key: |
 project-id: concierge
 `)
 
-	fakeCredsMarshalled := make(map[string]interface{})
+	fakeCredsMarshalled := make(map[string]any)
 	err := yaml.Unmarshal(creds, &fakeCredsMarshalled)
 	if err != nil {
 		t.Fatal(err)

internal/providers/k8s.go

@@ -102,7 +102,7 @@ func (k *K8s) CloudName() string { return "k8s" }
 func (k *K8s) GroupName() string { return "" }
 
 // Credentials reports the section of Juju's credentials.yaml for the provider
-func (m K8s) Credentials() map[string]interface{} { return nil }
+func (m K8s) Credentials() map[string]any { return nil }
 
 // ModelDefaults reports the Juju model-defaults specific to the provider.
 func (m *K8s) ModelDefaults() map[string]string { return m.modelDefaults }

internal/providers/lxd.go

@@ -81,7 +81,7 @@ func (l *LXD) CloudName() string { return "localhost" }
 func (l *LXD) GroupName() string { return "lxd" }
 
 // Credentials reports the section of Juju's credentials.yaml for the provider
-func (l *LXD) Credentials() map[string]interface{} { return nil }
+func (l *LXD) Credentials() map[string]any { return nil }
 
 // ModelDefaults reports the Juju model-defaults specific to the provider.
 func (l *LXD) ModelDefaults() map[string]string { return l.modelDefaults }

internal/providers/microk8s.go

@@ -108,7 +108,7 @@ func (m *MicroK8s) GroupName() string {
 }
 
 // Credentials reports the section of Juju's credentials.yaml for the provider
-func (m MicroK8s) Credentials() map[string]interface{} { return nil }
+func (m MicroK8s) Credentials() map[string]any { return nil }
 
 // ModelDefaults reports the Juju model-defaults specific to the provider.
 func (m *MicroK8s) ModelDefaults() map[string]string { return m.modelDefaults }

internal/providers/providers.go

@@ -30,7 +30,7 @@ type Provider interface {
 	// to allow non-root users to interact with the provider (where applicable).
 	GroupName() string
 	// Credentials reports the section of Juju's credentials.yaml for the provider.
-	Credentials() map[string]interface{}
+	Credentials() map[string]any
 	// ModelDefaults reports the Juju model-defaults specific to the provider.
 	ModelDefaults() map[string]string
 	// BootstrapConstraints reports the Juju bootstrap-constraints specific to the provider.

internal/snapd/client_test.go

@@ -12,22 +12,22 @@ import (
 // createTestServer creates a test HTTP server with a Unix socket listener.
 func createTestServer(t *testing.T, handler http.Handler) (*httptest.Server, string) {
 	t.Helper()
-	
+
 	// Create temporary directory for socket
 	tmpDir := t.TempDir()
 	socketPath := filepath.Join(tmpDir, "snapd.socket")
-	
+
 	// Create Unix listener
 	listener, err := net.Listen("unix", socketPath)
 	if err != nil {
 		t.Fatalf("Failed to create Unix listener: %v", err)
 	}
-	
+
 	// Create test server with custom listener
 	server := httptest.NewUnstartedServer(handler)
 	server.Listener = listener
 	server.Start()
-	
+
 	return server, socketPath
 }
 
@@ -36,7 +36,7 @@ func TestSnap_Success(t *testing.T) {
 		if r.URL.Path != "/v2/snaps/test-snap" {
 			t.Errorf("Expected path '/v2/snaps/test-snap', got: %s", r.URL.Path)
 		}
-		
+
 		resp := response{
 			Type:   "sync",
 			Status: "OK",
@@ -55,18 +55,18 @@ func TestSnap_Success(t *testing.T) {
 			t.Fatalf("failed to marshal snap: %v", err)
 		}
 		resp.Result = result
-		
+
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
 		json.NewEncoder(w).Encode(resp)
 	})
-	
+
 	server, socketPath := createTestServer(t, handler)
 	defer server.Close()
-	
+
 	client := NewClient(&Config{Socket: socketPath})
 	snap, err := client.Snap("test-snap")
-	
+
 	if err != nil {
 		t.Fatalf("Expected no error, got: %v", err)
 	}
@@ -90,13 +90,13 @@ func TestSnap_NotFound(t *testing.T) {
 		}
 		json.NewEncoder(w).Encode(resp)
 	})
-	
+
 	server, socketPath := createTestServer(t, handler)
 	defer server.Close()
-	
+
 	client := NewClient(&Config{Socket: socketPath})
 	_, err := client.Snap("nonexistent")
-	
+
 	if err == nil {
 		t.Fatal("Expected error for non-existent snap")
 	}
@@ -114,13 +114,13 @@ func TestSnap_UnexpectedStatusCode(t *testing.T) {
 		}
 		json.NewEncoder(w).Encode(resp)
 	})
-	
+
 	server, socketPath := createTestServer(t, handler)
 	defer server.Close()
-	
+
 	client := NewClient(&Config{Socket: socketPath})
 	_, err := client.Snap("test-snap")
-	
+
 	if err == nil {
 		t.Fatal("Expected error for 500 status code")
 	}
@@ -134,7 +134,7 @@ func TestFindOne_Success(t *testing.T) {
 		if r.URL.Query().Get("name") != "test-snap" {
 			t.Errorf("Expected query param name=test-snap, got: %s", r.URL.Query().Get("name"))
 		}
-		
+
 		resp := response{
 			Type:   "sync",
 			Status: "OK",
@@ -162,18 +162,18 @@ func TestFindOne_Success(t *testing.T) {
 			t.Fatalf("failed to marshal snaps response: %v", err)
 		}
 		resp.Result = result
-		
+
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
 		json.NewEncoder(w).Encode(resp)
 	})
-	
+
 	server, socketPath := createTestServer(t, handler)
 	defer server.Close()
-	
+
 	client := NewClient(&Config{Socket: socketPath})
 	snap, err := client.FindOne("test-snap")
-	
+
 	if err != nil {
 		t.Fatalf("Expected no error, got: %v", err)
 	}
@@ -194,13 +194,13 @@ func TestFindOne_NotFound(t *testing.T) {
 		}
 		json.NewEncoder(w).Encode(resp)
 	})
-	
+
 	server, socketPath := createTestServer(t, handler)
 	defer server.Close()
-	
+
 	client := NewClient(&Config{Socket: socketPath})
 	_, err := client.FindOne("nonexistent")
-	
+
 	if err == nil {
 		t.Fatal("Expected error for non-existent snap")
 	}
@@ -221,18 +221,18 @@ func TestFindOne_EmptyResults(t *testing.T) {
 			t.Fatalf("failed to marshal snaps: %v", err)
 		}
 		resp.Result = result
-		
+
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
 		json.NewEncoder(w).Encode(resp)
 	})
-	
+
 	server, socketPath := createTestServer(t, handler)
 	defer server.Close()
-	
+
 	client := NewClient(&Config{Socket: socketPath})
 	_, err := client.FindOne("nonexistent")
-	
+
 	if err == nil {
 		t.Fatal("Expected error for empty results")
 	}