feat: improve logger

[rosen-vladimirov]

Currently CLI's logger uses different ways to print messages on stdout and stderr:

• using log4js in some cases
• using console.log
• using process.stdout.write
• using process.stderr.write

Also, whenever we want to colorize the message, we include the colorization of the message in the message itself, before passing it to one of the methods above. This is a problem when CLI is used as a library, when it might not be used in a terminal environment - the messages contain terminal colorization. Also, in order to get the messages, you need to parse stdout and stderr of the process in which you've required CLI as a library.

To resolve the above, streamline the logger ways for handling messages - use log4js everywhere. This allows using different logging mechanism when CLI is used as a command line and when it is used as a library.
log4js has the concept of using appenders and layout when printing messages.

• appenders are responsible for output of log events. They may write events to files, send emails, store them in a database, or anything. Most appenders use layouts to serialise the events to strings for output.
• layout is a function for converting a LogEvent into a string representation.

Currently we have the several use cases for logging messages:

• print on stdout or stderr - for some of the methods we need to print errors and we want them to be shown on stderr. This can be handled in the appender, as it is the one which actually prints the message. To handle the case, pass useStderr property in the context of the LogEvent.
• add new line at the end of the message or skip it - in some cases we do not want to append new line at the end of the message. This logic is for the presentation of the message, so it can be handled in the layout. Check the value of skipNewLine property of the LogEvent context.
• wrap message with borders - in some cases, especially for command line usage, we want to wrap the message in some borders, to make it more visible to the user. This is a layout specific logic that can be handled based on the wrapMessageWithBorders property of the LogEvent context.

Each of the properties can be passed directly to each of the methods exposed from logger, i.e.:

const a = 1;
this.$logger.info("This is info message");
this.$logger.info("This is info message with placeholder %s", a);
this.$logger.info("This is info message without new line at the end", { skipNewLine: true });
this.$logger.info("This is info message with placeholder %s and without new line at the end,", a, { skipNewLine: true });
this.$logger.info("This is info message without new line at the end and printed on stderr", { skipNewLine: true, useStderr: true });
this.$logger.info("This is another info message without new line at the end and printed on stderr", { skipNewLine: true}, { useStderr: true });
this.$logger.info("This is info message with placeholder %s and without new line at the end printed on stderr", a, { skipNewLine: true, useStderr: true });
this.$logger.info("This is another info message with placeholder %s and without new line at the end printed on stderr", a, { skipNewLine: true }, { useStderr: true });

Full list of the properties that can be set is available in constants.LoggerConfigData.

When using CLI as a library, it makes sense to skip the colorization and instead of printing to stdout/stderr, to allow the consumer to take care of the messages on its own. In order to handle this, introduce an easy way for initializing the logger with different settings, i.e. appender, layout, level. This can be achieved through the logger.initialize method or initializeService.initialize method.
To make it easy when CLI is used as a library, introduce a custom emit-appender that emits the logged data instead of printing it. Its usage is fairly simple:

const tns = require("nativescript");
const { EventEmitter } = require("events");
const { EMIT_APPENDER_EVENT_NAME, LoggerAppenders } = tns.constants;
const emitter = new EventEmitter();
// IMPORTANT: Add the event handler before calling logger's initialize method.
// This is required as log4js makes a copy of the appenderOptions, where the emitter is passed
// NOTE: In case you want to debug the event handler, place `debugger` in it.
emitter.on(EMIT_APPENDER_EVENT_NAME, (logData) => {
	if (logData.loggingEvent.level.levelStr === LoggerLevel.WARN) {
		console.log(`WARNING: ${logData.formattedMessage}`);
	}
});

const logger = tns.logger;
logger.initialize({
	appenderOptions: {
		type: LoggerAppenders.emitAppender,
		emitter
	}
});

Additional code changes

During the implementation of the logger, several changes in other services were required:

• rename initService to projectInitService - it was required to make it easier to determine if the service is for initializing CLI or the project.
• remove progress-indicator - it was not used anywhere
• remove printMsgWithTimeout method from logger - it was used only in progress-indicator
• introduce initializeService - it is used to initialize CLI specific modules (like logger) and show all system warnings (for example for not supported macOS version). This way we no longer need to expose different methods when we want to show some warnings in the command line and when CLI is used as a library. We can just place them in the initialize method.
• remove warnWithLabel method from logger - it has been used on only two places and did not make sense to keep it.
• remove out method from logger - its usage is replaced with logger.info
• remove write method from logger - its intention was to print message on stdout, without modifying it (i.e. without adding new line, etc.), so it is replaced with info method and passing skipNewLine to true:

// OLD:
this.logger.write(line, platform, deviceIdentifier);
// NEW:
this.logger.info(line, platform, deviceIdentifier, { [LoggerConfigData.skipNewLine]: true });

• remove printInfoMessageOnSameLine method from logger - it was used to print messages on stdout without adding new line and only when log level is info. However, the implementation was incorrect (i.e. it was not checking the log level correctly). Replace the method with logger.info calls:

// OLD:
this.$logger.printInfoMessageOnSameLine("Waiting for emulator device initialization...");
// NEW:
this.$logger.info("Waiting for emulator device initialization...", { [LoggerConfigData.skipNewLine]: true });

• change logger.error to print to stderr instead of stdout.
• remove printOnStderr method from logger. This can be achieve with any log level by passing useStderr: true. Usage is replaced with logger.error.
• introduce initializeCliLogger method in logger, so it will be easy to setup CLI's log4js options
• introduce special layout function for CLI - based on the LoggingEvent context it changes the way message is printed. This layout should not be used when CLI is as a library.
• move all logger related files in a logger directory.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

What is the new behavior?

Implements #4602

[rosen-vladimirov]

test cli-smoke cli-create cli-plugin cli-preview cli-misc

[rosen-vladimirov]

test cli-smoke cli-misc

[rosen-vladimirov]

test cli-smoke cli-misc

[rosen-vladimirov]

test cli-smoke cli-create cli-plugin

[rosen-vladimirov]

test cli-smoke cli-misc