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Check out the Logger Aspect on

Create a logger#

In your extension, add LoggerMain as a dependency and create a new logger by running


Log to a file#

The following standard methods are available to log into a file. By default it's the debug.log file located at ~/Library/Caches/Bit/logs for Mac/Linux or %LOCALAPPDATA%\Bit for Windows.

logger.trace(message: string, ...meta: any[]);logger.debug(message: string, ...meta: any[]); string, ...meta: any[]);logger.warn(message: string, ...meta: any[]);logger.error(message: string, ...meta: any[]);

The message color is coded uniquely per extension-id. This way, it's easier to scroll the logs and distinguish between the extensions.

The format of the message logged to the file is "TIMESTAMP LEVEL: EXT-ID, MSG [META]". The "[META]" part is JSON.stringify of the second parameter in case it's an object. Otherwise, it's ignored.

JSON format is available as well. To use it, run bit config set log_json_format true.

It's possible to have the console as an extra layer so these messages will be printed to the screen as well, see below.

Log stack trace#

Normally, there is no need to log the Error object because it being caught by the end of the process and gets logged by Bit. Sometimes though it is needed to locally catch the error and continue, which can be useful to log the entire error object include the stack trace. In which case, pass the error object as the second parameter. e.g. catch(err) { logger.error('got an error during component-load', err); }

Log also to the console#

To see the same massages above printed into the screen, use the global flag --log [level]. For example, bit status --log=error. If the level was not entered, it defaults to info.

Alternatively, you can set an environment variable BIT_LOG with the desired level.

The format of the message logged to the console is "MSG [META]" The "[META]" part is the same as above.

Report progress#

During the command execution it's helpful to see the progress on the screen. The following options log to the file and in addition, print to the screen. Use only these methods and avoid calling console.log to not break the output (or potentially the JSON structure).

Please note that these methods print to the screen only when a command is not considered "internal" (such commands normally run on the remote server) and when a command is not used with --json flag. To specifically disable console-printing to a command, set the loader property to false.

Status Line (spinner)#

The status-line is a single line on the bottom of the screen, with a spinner/loader prefix. It's changing constantly during the command execution. This is the main indicator for the end-user of what's going on at the moment.

To set the text of this status-line, call:

logger.setStatusLine((text: string));

Once the command completed, the spinner is stopped and the status-line is cleared. Then, the command results are printed. If, for some reason, it is needed to clear the status-line before, just call logger.clearStatusLine().

Persist text#

Sometimes it's helpful to indicate that a phase has completed. Either successfully or failed. The following methods help with this:

// print to the screen with a green `โœ”` prefix. if message is empty, print the last logged message.logger.consoleSuccess(message?: string);
// print to the screen with a red `โœ–` prefix. if message is empty, print the last logged message.logger.consoleFailure(message?: string);

To print without any prefix, use logger.console(message);

Long Running Process Logger#

Run the following to get an instance of the LongProcessLogger and start logging the process description.

logger.createLongProcessLogger(processDescription: string, totalItems?: number): LongProcessLogger;

If the process involves iteration over a list of items, such as running tag on a list of components, then pass the totalItems as the total number of the components in the list.

Later, during the iteration, call logProgress(componentName) on the LongProcessLogger instance. once done, call end(), which logs the duration of the process in ms.

Here is an example of the messages produced by this longProcessLogger. The status-line always shows the last message.

teambit.workspace/workspace, loading components (total: 20)teambit.workspace/workspace, loading components (1/20). ui/buttonteambit.workspace/workspace, loading components (2/20). ui/form...teambit.workspace/workspace, loading components (20/20). ui/pageteambit.workspace/workspace, loading components (completed in 200ms)

An example when there is no totalItems.

teambit.workspace/workspace, loading componentsteambit.workspace/workspace, loading components (completed in 200ms)