feat(www): enable providers to send custom error responses via the dynamic key

Makefile

@@ -7,7 +7,7 @@ GOBIND=env PATH="$(GOBIN):$(PATH)" "$(GOMOBILE)" bind
 IMPORT_HOST=github.com
 IMPORT_PATH=$(IMPORT_HOST)/Jigsaw-Code/outline-client
 
-.PHONY: android apple linux windows
+.PHONY: android apple linux windows browser
 
 all: android apple linux windows
 
@@ -73,3 +73,6 @@ $(XGO): go.mod
 go.mod: tools.go
 	go mod tidy
 	touch go.mod
+
+browser:
+	echo 'browser environment: nothing to do'

src/www/app/outline_server_repository/access_key_serialization.ts

@@ -36,8 +36,16 @@ export function staticKeyToShadowsocksSessionConfig(staticKey: string): Shadowso
   }
 }
 
-function parseShadowsocksSessionConfigJson(maybeJsonText: string): ShadowsocksSessionConfig | null {
-  const {method, password, server, server_port, prefix} = JSON.parse(maybeJsonText);
+function parseShadowsocksSessionConfigJson(
+  maybeJsonText: string
+): ShadowsocksSessionConfig | errors.SessionConfigError | null {
+  const responseJson = JSON.parse(maybeJsonText);
+
+  if ('error' in responseJson) {
+    return responseJson.error;
+  }
+
+  const {method, password, server, server_port, prefix} = responseJson;
 
   // These are the mandatory keys.
   const missingKeys = [];

src/www/app/outline_server_repository/server.ts

@@ -96,7 +96,13 @@ export class OutlineServer implements Server {
 
   async connect() {
     if (this.type === ServerType.DYNAMIC_CONNECTION) {
-      this.sessionConfig = await fetchShadowsocksSessionConfig(this.sessionConfigLocation);
+      const sessionConfigOrError = await fetchShadowsocksSessionConfig(this.sessionConfigLocation);
+
+      if ('error' in sessionConfigOrError) {
+        throw new errors.SessionConfigFetchFailed((sessionConfigOrError.error as errors.SessionConfigError).message);
+      }
+
+      this.sessionConfig = sessionConfigOrError;
     }
 
     try {

src/www/model/errors.ts

@@ -15,6 +15,10 @@
 import {Server} from './server';
 import {CustomError} from '../../infrastructure/custom_error';
 
+export interface SessionConfigError {
+  message: string;
+}
+
 export class ServerAlreadyAdded extends CustomError {
   constructor(public readonly server: Server) {
     super();