Refactor credentials finder function (#2991)

To unblock unit-tests.

Signed-off-by: Artiom Diomin <artiom@kubermatic.com>

pkg/credentials/credentials.go

@@ -151,15 +151,15 @@ type ProviderEnvironmentVariable struct {
 }
 
 func Any(credentialsFilePath string) (map[string]string, error) {
-	credentialsFinder, err := newCredsFinder(credentialsFilePath, TypeUniversal)
+	credentialsFinder, err := newCredentialsFinder(withYAMLFile(credentialsFilePath))
 	if err != nil {
 		return nil, err
 	}
 
 	creds := map[string]string{}
 
 	for _, key := range allKeys {
-		if val := credentialsFinder(key); val != "" {
+		if val := credentialsFinder.get(key); val != "" {
 			creds[key] = val
 			// NB: We want to use Equinix Metal env vars everywhere, even if
 			// users has PACKET_ env vars on their systems.
@@ -178,11 +178,12 @@ func Any(credentialsFilePath string) (map[string]string, error) {
 
 // ProviderCredentials implements fetching credentials for each supported provider
 func ProviderCredentials(cloudProvider kubeoneapi.CloudProviderSpec, credentialsFilePath string, credentialsType Type) (map[string]string, error) {
-	credentialsFinder, err := newCredsFinder(credentialsFilePath, credentialsType)
+	credentialsFinderStore, err := newCredentialsFinder(withYAMLFile(credentialsFilePath), withType(credentialsType))
 	if err != nil {
 		return nil, err
 	}
 
+	credentialsFinder := credentialsFinderStore.lookupFunc()
 	switch {
 	case cloudProvider.AWS != nil:
 		return credentialsFinder.aws()
@@ -277,43 +278,76 @@ func ProviderCredentials(cloudProvider kubeoneapi.CloudProviderSpec, credentials
 	}
 }
 
-func newCredsFinder(credentialsFilePath string, credentialsType Type) (lookupFunc, error) {
-	staticMap := map[string]string{}
-	finder := func(name string) string {
-		switch {
-		case credentialsType != TypeUniversal:
-			typedName := string(credentialsType) + "_" + name
-			if val := os.Getenv(typedName); val != "" {
-				return val
-			}
-			if val, ok := staticMap[typedName]; ok && val != "" {
-				return val
-			}
+func withYAMLFile(filePath string) func(*credentialsFinder) error {
+	return func(cf *credentialsFinder) error {
+		if filePath == "" {
+			return nil
+		}
 
-			fallthrough
-		default:
-			if val := os.Getenv(name); val != "" {
-				return val
-			}
+		buf, err := os.ReadFile(filePath)
+		if err != nil {
+			return fail.Runtime(err, "reading credentials file")
+		}
 
-			return staticMap[name]
+		if err = yaml.Unmarshal(buf, &cf.static); err != nil {
+			return fail.Runtime(err, "unmarshalling credentials file")
 		}
+
+		return nil
 	}
+}
+
+func withType(typ Type) func(*credentialsFinder) error {
+	return func(cf *credentialsFinder) error {
+		cf.typ = typ
 
-	if credentialsFilePath == "" {
-		return finder, nil
+		return nil
 	}
+}
 
-	buf, err := os.ReadFile(credentialsFilePath)
-	if err != nil {
-		return nil, fail.Runtime(err, "loading credentials file")
+func newCredentialsFinder(opts ...func(*credentialsFinder) error) (*credentialsFinder, error) {
+	cf := credentialsFinder{
+		static:  map[string]string{},
+		dynamic: os.Getenv,
 	}
 
-	if err = yaml.Unmarshal(buf, &staticMap); err != nil {
-		return nil, fail.Runtime(err, "unmarshalling credentials file")
+	for _, optFn := range opts {
+		if err := optFn(&cf); err != nil {
+			return nil, err
+		}
+	}
+
+	return &cf, nil
+}
+
+type credentialsFinder struct {
+	static  map[string]string
+	dynamic func(string) string
+	typ     Type
+}
+
+func (cf *credentialsFinder) lookupFunc() lookupFunc { return cf.get }
+
+func (cf *credentialsFinder) typedKey(name string) string {
+	return string(cf.typ) + "_" + name
+}
+
+func (cf *credentialsFinder) fetch(name string) string {
+	if val := cf.static[name]; val != "" {
+		return val
+	}
+
+	return cf.dynamic(name)
+}
+
+func (cf *credentialsFinder) get(name string) string {
+	if cf.typ != TypeUniversal {
+		if val := cf.fetch(cf.typedKey(name)); val != "" {
+			return val
+		}
 	}
 
-	return finder, nil
+	return cf.fetch(name)
 }
 
 // lookupFunc is function that retrieves credentials from the sources

pkg/credentials/credentials_test.go

@@ -248,3 +248,95 @@ func TestVmwareCloudDirectorValidationFunc(t *testing.T) {
 		})
 	}
 }
+
+func TestCredentialsFinder(t *testing.T) {
+	withDynamicFixture := func(dynamicFn func(string) string) func(*credentialsFinder) error {
+		return func(cf *credentialsFinder) error {
+			cf.dynamic = dynamicFn
+
+			return nil
+		}
+	}
+
+	withStaticFixture := func(static map[string]string) func(*credentialsFinder) error {
+		return func(cf *credentialsFinder) error {
+			cf.static = static
+
+			return nil
+		}
+	}
+
+	tests := []struct {
+		name string
+		key  string
+		want string
+		opts []func(*credentialsFinder) error
+	}{
+		{
+			name: "static universal",
+			key:  "key1",
+			want: "val1",
+			opts: []func(*credentialsFinder) error{
+				withStaticFixture(map[string]string{
+					"key1": "val1",
+				}),
+			},
+		},
+		{
+			name: "static with type OSM",
+			key:  "key1",
+			want: "OSM_val1",
+			opts: []func(*credentialsFinder) error{
+				withType(TypeOSM),
+				withStaticFixture(map[string]string{
+					"OSM_key1": "OSM_val1",
+				}),
+			},
+		},
+		{
+			name: "dynamic with type OSM",
+			key:  "key1",
+			want: "OSM_val1",
+			opts: []func(*credentialsFinder) error{
+				withType(TypeOSM),
+				withStaticFixture(map[string]string{
+					"key1": "from_static",
+				}),
+				withDynamicFixture(func(key string) string {
+					return map[string]string{
+						"OSM_key1": "OSM_val1",
+					}[key]
+				}),
+			},
+		},
+		{
+			name: "static precedence over dynamic with type OSM",
+			key:  "key1",
+			want: "from_static",
+			opts: []func(*credentialsFinder) error{
+				withType(TypeOSM),
+				withStaticFixture(map[string]string{
+					"OSM_key1": "from_static",
+				}),
+				withDynamicFixture(func(key string) string {
+					return map[string]string{
+						"OSM_key1": "from_dynamic",
+					}[key]
+				}),
+			},
+		},
+	}
+
+	for _, tcase := range tests {
+		t.Run(tcase.name, func(t *testing.T) {
+			finder, err := newCredentialsFinder(tcase.opts...)
+			if err != nil {
+				t.Fatalf("got unexpcted error: %v", err)
+			}
+
+			if result := finder.get(tcase.key); result != tcase.want {
+				t.Errorf("get(%q)=%q, want %q", tcase.key, result, tcase.want)
+			}
+		})
+	}
+}