Ben Konyi
60b217ff2d
Also cleans up some references to Observatory in various places. Work towards https://github.com/dart-lang/sdk/issues/50233 TEST=N/A CoreLibraryReviewExempt: Not modifying public core libraries. Change-Id: I1f36b4e6f1fd9a59a579d719aafa599906eedb3f Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/429141 Reviewed-by: Siva Annamalai <asiva@google.com> Commit-Queue: Ben Konyi <bkonyi@google.com>
61 lines
2.7 KiB
Markdown
61 lines
2.7 KiB
Markdown
# Debugging Plugins
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Unfortunately, debugging a plugin is not well supported at this point. The
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server is typically run as a sub-process by a client. Some clients provide a way
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to add command-line arguments when invoking the server, others don't. To make
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matters worse, each plugin is run in a separate isolate.
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Nevertheless, there are a few ways to get some information about what's going on
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in a plugin. Those are outlined below. If you know of other useful techniques,
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or if you have a request for better support, please let us know.
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## Check the Status Pages
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The analysis server has the ability to host a set of web pages that describe the
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current state of the server. One of the pieces of information available through
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those pages is a list of the plugins that are currently being run.
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The server does not host these pages unless it has been requested to do so. You
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can request it by passing a command-line argument to the server when it is being
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started. The argument should be similar to `--port=10000` (any valid port number
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will work). You can then point your browser to `http://localhost:10000/status`.
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If you're using IntelliJ as your client, there is a gear icon on the Dart
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Analysis view's header that can be used to open the status pages.
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The plugin information can be displayed by clicking on "Plugins" in the list on
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the left.
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## Check the Instrumentation Log
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The analysis server has the ability to log debugging data to a file. For
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historic reasons this file is referred to as the _instrumentation log_. The data
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primarily consists of a record of the communications between the server and both
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the client that started it and any plugins that the server is running.
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The server does not write to this file unless it has been requested to do so.
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You can request it by passing a command-line argument to the server when it is
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being started. The argument should be similar to
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`--instrumentation-log-file=/path/to/file.txt`.
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## Println Debugging
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You cannot use the `print` function to get debugging information because server
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is run by the client in a child process, and hence doesn't have the ability to
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write to the console.
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The closest approximation is for the plugin to send notifications to the server
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that will be written to the instrumentation log file. Currently, the best choice
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for this is the `plugin.error` notification. Just be sure that `isFatal` has a
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value of `false`.
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## Using Dart DevTools
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If the client you're using allows you to pass command-line flags to the VM, then
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you can also run the analysis server under Dart DevTools. Pass in both
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`--observe` and `--pause-isolates-on-start`, then point your browser to
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`http://localhost:8181`.
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If you're using IntelliJ as your client, open the "Registry..." dialog and edit
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the entry named "dart.server.vm.options".
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