pkg/analyzer_plugin/doc/tutorial/debugging.md - sdk.git - Git at Google

 # Debugging Plugins

 Unfortunately, debugging a plugin is not well supported at this point. The
 server is typically run as a sub-process by a client. Some clients provide a way
 to add command-line arguments when invoking the server, others don't. To make
 matters worse, each plugin is run in a separate isolate.

 Nevertheless, there are a few ways to get some information about what's going on
 in a plugin. Those are outlined below. If you know of other useful techniques,
 or if you have a request for better support, please let us know.

 ## Check the Status Pages

 The analysis server has the ability to host a set of web pages that describe the
 current state of the server. One of the pieces of information available through
 those pages is a list of the plugins that are currently being run.

 The server does not host these pages unless it has been requested to do so. You
 can request it by passing a command-line argument to the server when it is being
 started. The argument should be similar to `--port=10000` (any valid port number
 will work). You can then point your browser to `http://localhost:10000/status`.

 If you're using IntelliJ as your client, there is a gear icon on the Dart
 Analysis view's header that can be used to open the status pages.

 The plugin information can be displayed by clicking on "Plugins" in the list on
 the left.

 ## Check the Instrumentation Log

 The analysis server has the ability to log debugging data to a file. For
 historic reasons this file is referred to as the _instrumentation log_. The data
 primarily consists of a record of the communications between the server and both
 the client that started it and any plugins that the server is running.

 The server does not write to this file unless it has been requested to do so.
 You can request it by passing a command-line argument to the server when it is
 being started. The argument should be similar to
 `--instrumentation-log-file=/path/to/file.txt`.

 ## Println Debugging

 You cannot use the `print` function to get debugging information because server
 is run by the client in a child process, and hence doesn't have the ability to
 write to the console.

 The closest approximation is for the plugin to send notifications to the server
 that will be written to the instrumentation log file. Currently, the best choice
 for this is the `plugin.error` notification. Just be sure that `isFatal` has a
 value of `false`.

 ## Using Observatory

 If the client you're using allows you to pass command-line flags to the VM, then
 you can also run the analysis server under the Observatory. Pass in both
 `--observe` and `--pause-isolates-on-start`, then point your browser to
 `http://localhost:8181`. To learn more, see the
 [observatory][observatory] documentation.

 If you're using IntelliJ as your client, open the "Registry..." dialog and edit
 the entry named "dart.server.vm.options".

 [observatory]: https://dart-lang.github.io/observatory/
	# Debugging Plugins

	Unfortunately, debugging a plugin is not well supported at this point. The
	server is typically run as a sub-process by a client. Some clients provide a way
	to add command-line arguments when invoking the server, others don't. To make
	matters worse, each plugin is run in a separate isolate.

	Nevertheless, there are a few ways to get some information about what's going on
	in a plugin. Those are outlined below. If you know of other useful techniques,
	or if you have a request for better support, please let us know.

	## Check the Status Pages

	The analysis server has the ability to host a set of web pages that describe the
	current state of the server. One of the pieces of information available through
	those pages is a list of the plugins that are currently being run.

	The server does not host these pages unless it has been requested to do so. You
	can request it by passing a command-line argument to the server when it is being
	started. The argument should be similar to `--port=10000` (any valid port number
	will work). You can then point your browser to `http://localhost:10000/status`.

	If you're using IntelliJ as your client, there is a gear icon on the Dart
	Analysis view's header that can be used to open the status pages.

	The plugin information can be displayed by clicking on "Plugins" in the list on
	the left.

	## Check the Instrumentation Log

	The analysis server has the ability to log debugging data to a file. For
	historic reasons this file is referred to as the _instrumentation log_. The data
	primarily consists of a record of the communications between the server and both
	the client that started it and any plugins that the server is running.

	The server does not write to this file unless it has been requested to do so.
	You can request it by passing a command-line argument to the server when it is
	being started. The argument should be similar to
	`--instrumentation-log-file=/path/to/file.txt`.

	## Println Debugging

	You cannot use the `print` function to get debugging information because server
	is run by the client in a child process, and hence doesn't have the ability to
	write to the console.

	The closest approximation is for the plugin to send notifications to the server
	that will be written to the instrumentation log file. Currently, the best choice
	for this is the `plugin.error` notification. Just be sure that `isFatal` has a
	value of `false`.

	## Using Observatory

	If the client you're using allows you to pass command-line flags to the VM, then
	you can also run the analysis server under the Observatory. Pass in both
	`--observe` and `--pause-isolates-on-start`, then point your browser to
	`http://localhost:8181`. To learn more, see the
	[observatory][observatory] documentation.

	If you're using IntelliJ as your client, open the "Registry..." dialog and edit
	the entry named "dart.server.vm.options".

	[observatory]: https://dart-lang.github.io/observatory/