Organize Errors in GitHub Auth and make sure no double prompting happens (#180734)

* Organize Errors in GitHub Auth and make sure no double prompting happens

This mostly just moves some strings into variables... but this also fixes the GH Auth side of https://github.com/microsoft/vscode/issues/180697 so you should only be asked once if you want to try a different way to log in.

* add comments

extensions/github-authentication/src/githubServer.ts

@@ -16,6 +16,13 @@ import { fetching } from './node/fetch';
 
 const CLIENT_ID = '01ab8ac9400c4e429b23';
 const GITHUB_TOKEN_URL = 'https://vscode.dev/codeExchangeProxyEndpoints/github/login/oauth/access_token';
+
+// This is the error message that we throw if the login was cancelled for any reason. Extensions
+// calling `getSession` can handle this error to know that the user cancelled the login.
+const CANCELLATION_ERROR = 'Cancelled';
+// These error messages are internal and should not be shown to the user in any way.
+const TIMED_OUT_ERROR = 'Timed out';
+const USER_CANCELLATION_ERROR = 'User Cancelled';
 const NETWORK_ERROR = 'network error';
 
 const REDIRECT_URL_STABLE = 'https://vscode.dev/redirect';
@@ -132,7 +139,7 @@ export class GitHubServer implements IGitHubServer {
 				: vscode.l10n.t('You have not yet finished authorizing this extension to use GitHub. Would you like to keep trying?');
 			const result = await vscode.window.showWarningMessage(message, yes, no);
 			if (result !== yes) {
-				throw new Error('Cancelled');
+				throw new Error(CANCELLATION_ERROR);
 			}
 		};
 
@@ -146,7 +153,7 @@ export class GitHubServer implements IGitHubServer {
 				return await this.doLoginWithoutLocalServer(scopes, nonce, callbackUri);
 			} catch (e) {
 				this._logger.error(e);
-				userCancelled = e.message ?? e === 'User Cancelled';
+				userCancelled = e.message ?? e === USER_CANCELLATION_ERROR;
 			}
 		}
 
@@ -163,8 +170,7 @@ export class GitHubServer implements IGitHubServer {
 				await promptToContinue();
 				return await this.doLoginWithLocalServer(scopes);
 			} catch (e) {
-				this._logger.error(e);
+				userCancelled = this.processLoginError(e);
-				userCancelled = e.message ?? e === 'User Cancelled';
 			}
 		}
 
@@ -174,8 +180,7 @@ export class GitHubServer implements IGitHubServer {
 				await promptToContinue();
 				return await this.doLoginDeviceCodeFlow(scopes);
 			} catch (e) {
-				this._logger.error(e);
+				userCancelled = this.processLoginError(e);
-				userCancelled = e.message ?? e === 'User Cancelled';
 			}
 		}
 
@@ -186,12 +191,11 @@ export class GitHubServer implements IGitHubServer {
 				await promptToContinue();
 				return await this.doLoginWithPat(scopes);
 			} catch (e) {
-				this._logger.error(e);
+				userCancelled = this.processLoginError(e);
-				userCancelled = e.message ?? e === 'User Cancelled';
 			}
 		}
 
-		throw new Error(userCancelled ? 'Cancelled' : 'No auth flow succeeded.');
+		throw new Error(userCancelled ? CANCELLATION_ERROR : 'No auth flow succeeded.');
 	}
 
 	private async doLoginWithoutLocalServer(scopes: string, nonce: string, callbackUri: vscode.Uri): Promise<string> {
@@ -232,8 +236,8 @@ export class GitHubServer implements IGitHubServer {
 			try {
 				return await Promise.race([
 					codeExchangePromise.promise,
-					new Promise<string>((_, reject) => setTimeout(() => reject('Timed out'), 300_000)), // 5min timeout
+					new Promise<string>((_, reject) => setTimeout(() => reject(TIMED_OUT_ERROR), 300_000)), // 5min timeout
-					promiseFromEvent<any, any>(token.onCancellationRequested, (_, __, reject) => { reject('User Cancelled'); }).promise
+					promiseFromEvent<any, any>(token.onCancellationRequested, (_, __, reject) => { reject(USER_CANCELLATION_ERROR); }).promise
 				]);
 			} finally {
 				this._pendingNonces.delete(scopes);
@@ -273,8 +277,8 @@ export class GitHubServer implements IGitHubServer {
 				vscode.env.openExternal(vscode.Uri.parse(`http://127.0.0.1:${port}/signin?nonce=${encodeURIComponent(server.nonce)}`));
 				const { code } = await Promise.race([
 					server.waitForOAuthResponse(),
-					new Promise<any>((_, reject) => setTimeout(() => reject('Timed out'), 300_000)), // 5min timeout
+					new Promise<any>((_, reject) => setTimeout(() => reject(TIMED_OUT_ERROR), 300_000)), // 5min timeout
-					promiseFromEvent<any, any>(token.onCancellationRequested, (_, __, reject) => { reject('User Cancelled'); }).promise
+					promiseFromEvent<any, any>(token.onCancellationRequested, (_, __, reject) => { reject(USER_CANCELLATION_ERROR); }).promise
 				]);
 				codeToExchange = code;
 			} finally {
@@ -317,7 +321,7 @@ export class GitHubServer implements IGitHubServer {
 			}, button);
 
 		if (modalResult !== button) {
-			throw new Error('User Cancelled');
+			throw new Error(USER_CANCELLATION_ERROR);
 		}
 
 		await vscode.env.clipboard.writeText(json.user_code);
@@ -340,14 +344,14 @@ export class GitHubServer implements IGitHubServer {
 			}, button);
 
 		if (modalResult !== button) {
-			throw new Error('User Cancelled');
+			throw new Error(USER_CANCELLATION_ERROR);
 		}
 
 		const description = `${vscode.env.appName} (${scopes})`;
 		const uriToOpen = await vscode.env.asExternalUri(this.baseUri.with({ path: '/settings/tokens/new', query: `description=${description}&scopes=${scopes.split(' ').join(',')}` }));
 		await vscode.env.openExternal(uriToOpen);
 		const token = await vscode.window.showInputBox({ placeHolder: `ghp_1a2b3c4...`, prompt: `GitHub Personal Access Token - ${scopes}`, ignoreFocusOut: true });
-		if (!token) { throw new Error('User Cancelled'); }
+		if (!token) { throw new Error(USER_CANCELLATION_ERROR); }
 
 		const tokenScopes = await getScopes(token, this.getServerUri('/'), this._logger); // Example: ['repo', 'user']
 		const scopesList = scopes.split(' '); // Example: 'read:user repo user:email'
@@ -392,7 +396,7 @@ export class GitHubServer implements IGitHubServer {
 			for (let i = 0; i < attempts; i++) {
 				await new Promise(resolve => setTimeout(resolve, json.interval * 1000));
 				if (token.isCancellationRequested) {
-					throw new Error('User Cancelled');
+					throw new Error(USER_CANCELLATION_ERROR);
 				}
 				let accessTokenResult;
 				try {
@@ -423,7 +427,7 @@ export class GitHubServer implements IGitHubServer {
 				return accessTokenJson.access_token;
 			}
 
-			throw new Error('Cancelled');
+			throw new Error(TIMED_OUT_ERROR);
 		});
 	}
 
@@ -641,4 +645,12 @@ export class GitHubServer implements IGitHubServer {
 			// No-op
 		}
 	}
+
+	private processLoginError(error: Error): boolean {
+		if (error.message === CANCELLATION_ERROR) {
+			throw error;
+		}
+		this._logger.error(error.message ?? error);
+		return error.message === USER_CANCELLATION_ERROR;
+	}
 }