a13ccfd0f5
Generated by https://github.com/jsoref/spelling `f`; to maintain your repo, please consider `fchurn` I generally try to ignore upstream bits. I've accidentally included some items from the `deps/` directory. I expect someone will give me a list of items to drop, I'm happy to drop whole files/directories, or to split the PR into multiple items (E.g. comments/locals/public). Closes #4294
108 lines
6.3 KiB
Markdown
108 lines
6.3 KiB
Markdown
---
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author: Dustin Howett @DHowett-MSFT
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created on: 2019-07-19
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last updated: 2019-11-05
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issue id: "#2563"
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---
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# Improvements to CloseOnExit
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## Abstract
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This specification describes an improvement to the `closeOnExit` profile feature and the `ITerminalConnection` interface that will offer greater flexibility and allow us to provide saner defaults in the face of unreliable software.
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### Conventions and Terminology
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119](https://tools.ietf.org/html/rfc2119).
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## Inspiration
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Other terminal emulators like ConEmu have a similar feature.
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## Solution Design
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### `ITerminalConnection` Changes
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* The `TerminalConnection` interface will be augmented with an enumerator and a set of events regarding connection state transitions.
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* enum `TerminalConnection::ConnectionState`
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* This enum attempts to encompass all potential connection states, even those which do not make sense for a local terminal.
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* The wide variety of values will be useful to indicate state changes in a user interface.
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* `NotConnected`: All new connections will start out in this state
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* `Connecting`: The connection has been initiated, but has not yet completed connecting.
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* `Connected`: The connection is active.
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* `Closing`: The connection is being closed (usually by request).
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* `Closed`: The connection has been closed, either by request or from the remote end terminating successfully.
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* `Failed`: The connection was unexpectedly terminated.
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* event `StateChanged(ITerminalConnection, IInspectable)`
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* (the `IInspectable` argument is recommended and required for a typed event handler, but it will bear no payload.)
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* event `TerminalDisconnected` will be removed, as it is replaced by `StateChanged`
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* **NOTE**: A conforming implementation MUST treat states as a directed acyclic graph. States MUST NOT be transitioned in reverse.
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* A helper class may be provided for managing state transitions.
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### `TerminalControl` Changes
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* As the decision as to whether to close a terminal control hosting a connection that has transitioned into a terminal state will be made by the application, the unexpressive `Close` event will be removed and replaced with a `ConnectionStateChanged` event.
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* `event ConnectionStateChanged(TerminalControl, IInspectable)` event will project its connection's `StateChanged` event.
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* TerminalControl's new `ConnectionState` will project its connection's `State`.
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* (this is indicated for an eventual data binding; see Future Considerations.)
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### Application and Settings
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1. The existing `closeOnExit` profile key will be replaced with an enumerated string key supporting the following values (behaviors):
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* `always` - a tab or pane hosting this profile will always be closed when the launched connection reaches a terminal state.
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* `graceful` - a tab or pane hosting this profile will be closed if and only if the launched connection reaches the `Closed` terminal state.
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* `never` - a tab or pane hosting this profile will not automatically close.
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* See the Compatibility section for information on the legacy settings transition.
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* **The new default value for `closeOnExit` will be `graceful`.**
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2. `Pane` will remain responsible for making the final determination as to whether it is closed based on the settings of the profile it is hosting.
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## UI/UX Design
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* The existing `ITerminalConnection` implementations will be augmented to print out interesting and useful status information when they transition into a `Closed` or `Failed` state.
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* Example (ConPTY connection)
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* The pseudoconsole cannot be opened, or the process fails to launch.<br>`[failed to spawn 'thing': 0x80070002]`, transition to `Failed`.
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* The process exited unexpectedly.<br>`[process exited with code 300]`, transition to `Failed`.
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* The process exited normally.<br>`[process exited with code 0]`, transition to `Closed`.
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* _The final message will always be printed_ regardless of user configuration.
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* If the user's settings specify `closeOnExit: never/false`, the terminal hosting the connection will never be automatically closed. The message will remain on-screen.
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* If the user's settings specify `closeOnExit: graceful/true`, the terminal hosting the connection _will_ automatically be closed if the connection's state is `Closed`. A connection in the `Failed` state will not be closed, and the message will remain on-screen.
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* If the user's settings specify `closeOnExit: always`, the terminal hosting the connection will be closed. The message will not be seen.
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## Capabilities
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### Accessibility
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This will give users of all technologies a way to know when their shell has failed to launch or has exited with an unexpected status code.
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### Security
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There will be no impact to security.
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### Reliability
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Windows Terminal will no longer immediately terminate on startup if the user's shell doesn't exist.
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### Compatibility
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There is an existing `closeOnExit` _boolean_ key that a user may have configured in profiles.json. The boolean values should map as follows:
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* `true` -> `graceful`
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* `false` -> `never`
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This will make for a clean transition to Windows Terminal's sane new defaults.
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### Performance, Power, and Efficiency
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## Potential Issues
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There will be no impact to Performance, Power or Efficiency.
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## Future considerations
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* Eventually, we may want to implement a feature like "only close on graceful exit if the shell was running for more than X seconds". This puts us in a better position to do that, as we can detect graceful and clumsy exits more readily.
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* (potential suggestion: `{ "closeOnExit": "10s" }`
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* The enumerator values for transitioning connection states will be useful for connections that require internet access.
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* Since the connection states are exposed through `TerminalControl`, they should be able to be data-bound to other Xaml elements. This can be used to provide discrete UI states for terminal controls, panes or tabs _hosting_ terminal controls.
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* Example: a tab hosting a terminal control whose connection has been broken MAY display a red border.
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* Example: an inactive tab that reaches the `Connected` state MAY flash to indicate that it is ready.
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