Enhance alias logs function

* alias logs will now pull the latest version logs from “Lambda”
service directly if --version flag is not specificed.
* Added --version flag to alias logs, so that user can view logs of a
specific version of function.

Author: Roy Hui

index.js

@@ -177,6 +177,9 @@ class AwsAlias {
 			logCommand.options.alias = {
 				usage: 'Alias'
 			};
+			logCommand.options.version = {
+				usage: 'Logs a specific version of the function'
+			};
 			logCommand.commands = _.assign({}, logCommand.commands, {
 				api: {
 					usage: 'Output the logs of a deployed APIG stage (alias)',

lib/logs.js

@@ -55,14 +55,16 @@ module.exports = {
 			orderBy: 'LastEventTime',
 		};
 
+		let aliasGetAliasFunctionVersion
+		// Check if --version is specified
+		if (this._options.version) {
+			aliasGetAliasFunctionVersion = Promise.resolve(this._options.version)
+		} else {
+			aliasGetAliasFunctionVersion = this.aliasGetAliasLatestFunctionVersionByFunctionName(this._alias, this._lambdaName)
+		}
 		// Get currently deployed function version for the alias to
 		// setup the stream filter correctly
-		return this.aliasGetAliasFunctionVersions(this._alias)
-		.then(versions => {
-			return _.map(
-				_.filter(versions, [ 'functionName', this._lambdaName ]),
-				version => version.functionVersion);
-		})
+		return aliasGetAliasFunctionVersion
 		.then(version => {
 			return this.provider
 				.request('CloudWatchLogs',
@@ -75,7 +77,6 @@ module.exports = {
 						throw new this.serverless.classes
 							.Error('No existing streams for the function alias');
 					}
-
 					return _.map(
 						_.filter(reply.logStreams, stream => _.includes(stream.logStreamName, `[${version}]`)),
 						stream => stream.logStreamName);
@@ -124,6 +125,10 @@ module.exports = {
 	},
 
 	functionLogsShowLogs(logStreamNames) {
+		if (logStreamNames.length === 0) {
+			throw new this.serverless.classes
+				.Error('No existing streams for the latest version of function alias. If you want to view logs of a specific function version, please use --version to specify');
+		}
 		const formatLambdaLogEvent = event => {
 			const msgParam = event.message;
 			let msg = msgParam;

lib/stackInformation.js

@@ -181,4 +181,15 @@ module.exports = {
 		});
 	},
 
+	aliasGetAliasLatestFunctionVersionByFunctionName(aliasName, functionName) {
+		return this._provider.request('Lambda',
+			'getAlias',
+			{ FunctionName: functionName, Name: aliasName },
+			this._options.stage,
+			this._options.region)
+			.then(result => {
+				return result.FunctionVersion
+			})
+	},
+
 };