fix/config: merge env additional headers over config file headers (#1359)

* fix/config: merge env additional headers over config file headers

Previously env-derived additional headers overwrote any additionalHeaders
loaded from the config file entirely. Merge them instead, with env headers
taking precedence, consistent with how the access token and endpoint are
overridden. Config-file keys are normalized to lowercase to match the
env-header convention, so env values correctly override differently-cased
config keys and the authorization-conflict check catches them.

* chore/config: condense additional-headers merge comment

Author: BolajiOlajide

cmd/src/main.go

@@ -337,7 +337,16 @@ func readConfig() (*config, error) {
 		}
 	}
 
-	cfg.additionalHeaders = parseAdditionalHeaders()
+	// Merge config-file headers under the env headers (which take precedence),
+	// lowercasing config keys to match the env-header convention.
+	envHeaders := parseAdditionalHeaders()
+	for k, v := range cfg.additionalHeaders {
+		lk := strings.ToLower(k)
+		if _, ok := envHeaders[lk]; !ok {
+			envHeaders[lk] = v
+		}
+	}
+	cfg.additionalHeaders = envHeaders
 	// Ensure that we're not clashing additonal headers
 	_, hasAuthorizationAdditonalHeader := cfg.additionalHeaders["authorization"]
 	if cfg.accessToken != "" && hasAuthorizationAdditonalHeader {

cmd/src/main_test.go

@@ -358,6 +358,63 @@ func TestReadConfig(t *testing.T) {
 				inCI:              true,
 			},
 		},
+		{
+			name: "config file additional headers preserved when endpoint/token from environment",
+			fileContents: &configFromFile{
+				Endpoint:          "https://example.com/",
+				AccessToken:       "deadbeef",
+				AdditionalHeaders: map[string]string{"x-proxy-token": "secret"},
+			},
+			envToken:    "abc",
+			envEndpoint: "https://override.com",
+			want: &config{
+				endpointURL:       &url.URL{Scheme: "https", Host: "override.com"},
+				accessToken:       "abc",
+				additionalHeaders: map[string]string{"x-proxy-token": "secret"},
+			},
+		},
+		{
+			name: "config file additional headers merged with environment headers",
+			fileContents: &configFromFile{
+				Endpoint:          "https://example.com/",
+				AccessToken:       "deadbeef",
+				AdditionalHeaders: map[string]string{"x-proxy-token": "secret"},
+			},
+			envFooHeader: "bar",
+			want: &config{
+				endpointURL:       &url.URL{Scheme: "https", Host: "example.com"},
+				accessToken:       "deadbeef",
+				additionalHeaders: map[string]string{"x-proxy-token": "secret", "foo": "bar"},
+			},
+		},
+		{
+			name: "environment headers override config file headers",
+			fileContents: &configFromFile{
+				Endpoint:          "https://example.com/",
+				AccessToken:       "deadbeef",
+				AdditionalHeaders: map[string]string{"foo": "from-config"},
+			},
+			envFooHeader: "from-env",
+			want: &config{
+				endpointURL:       &url.URL{Scheme: "https", Host: "example.com"},
+				accessToken:       "deadbeef",
+				additionalHeaders: map[string]string{"foo": "from-env"},
+			},
+		},
+		{
+			name: "environment headers override differently-cased config file headers",
+			fileContents: &configFromFile{
+				Endpoint:          "https://example.com/",
+				AccessToken:       "deadbeef",
+				AdditionalHeaders: map[string]string{"Foo": "from-config"},
+			},
+			envFooHeader: "from-env",
+			want: &config{
+				endpointURL:       &url.URL{Scheme: "https", Host: "example.com"},
+				accessToken:       "deadbeef",
+				additionalHeaders: map[string]string{"foo": "from-env"},
+			},
+		},
 	}
 
 	for _, test := range tests {