# Description
When implementing a `Command`, one must also import all the types
present in the function signatures for `Command`. This makes it so that
we often import the same set of types in each command implementation
file. E.g., something like this:
```rust
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
ShellError, Signature, Span, Type, Value,
};
```
This PR adds the `nu_engine::command_prelude` module which contains the
necessary and commonly used types to implement a `Command`:
```rust
// command_prelude.rs
pub use crate::CallExt;
pub use nu_protocol::{
ast::{Call, CellPath},
engine::{Command, EngineState, Stack},
record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, IntoSpanned,
PipelineData, Record, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
};
```
This should reduce the boilerplate needed to implement a command and
also gives us a place to track the breadth of the `Command` API. I tried
to be conservative with what went into the prelude modules, since it
might be hard/annoying to remove items from the prelude in the future.
Let me know if something should be included or excluded.
# Description
Adds a `nu-plugin-test-support` crate with an interface that supports
testing plugins.
Unlike in reality, these plugins run in the same process on separate
threads. This will allow
testing aspects of the plugin internal state and handling serialized
plugin custom values easily.
We still serialize their custom values and all of the engine to plugin
logic is still in play, so
from a logical perspective this should still expose any bugs that would
have been caused by that.
The only difference is that it doesn't run in a different process, and
doesn't try to serialize
everything to the final wire format for stdin/stdout.
TODO still:
- [x] Clean up warnings about private types exposed in trait definition
- [x] Automatically deserialize plugin custom values in the result so
they can be inspected
- [x] Automatic plugin examples test function
- [x] Write a bit more documentation
- [x] More tests
- [x] Add MIT License file to new crate
# User-Facing Changes
Plugin developers get a nice way to test their plugins.
# Tests + Formatting
Run the tests with `cargo test -p nu-plugin-test-support --
--show-output` to see some examples of what the failing test output for
examples can look like. I used the `difference` crate (MIT licensed) to
make it look nice.
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`
# After Submitting
- [ ] Add a section to the book about testing
- [ ] Test some of the example plugins this way
- [ ] Add example tests to nu_plugin_template so plugin developers have
something to start with
# Description
This allows plugins to make calls back to the engine to get config,
evaluate closures, and do other things that must be done within the
engine process.
Engine calls can both produce and consume streams as necessary. Closures
passed to plugins can both accept stream input and produce stream output
sent back to the plugin.
Engine calls referring to a plugin call's context can be processed as
long either the response hasn't been received, or the response created
streams that haven't ended yet.
This is a breaking API change for plugins. There are some pretty major
changes to the interface that plugins must implement, including:
1. Plugins now run with `&self` and must be `Sync`. Executing multiple
plugin calls in parallel is supported, and there's a chance that a
closure passed to a plugin could invoke the same plugin. Supporting
state across plugin invocations is left up to the plugin author to do in
whichever way they feel best, but the plugin object itself is still
shared. Even though the engine doesn't run multiple plugin calls through
the same process yet, I still considered it important to break the API
in this way at this stage. We might want to consider an optional
threadpool feature for performance.
2. Plugins take a reference to `EngineInterface`, which can be cloned.
This interface allows plugins to make calls back to the engine,
including for getting config and running closures.
3. Plugins no longer take the `config` parameter. This can be accessed
from the interface via the `.get_plugin_config()` engine call.
# User-Facing Changes
<!-- List of all changes that impact the user experience here. This
helps us keep track of breaking changes. -->
Not only does this have plugin protocol changes, it will require plugins
to make some code changes before they will work again. But on the plus
side, the engine call feature is extensible, and we can add more things
to it as needed.
Plugin maintainers will have to change the trait signature at the very
least. If they were using `config`, they will have to call
`engine.get_plugin_config()` instead.
If they were using the mutable reference to the plugin, they will have
to come up with some strategy to work around it (for example, for `Inc`
I just cloned it). This shouldn't be such a big deal at the moment as
it's not like plugins have ever run as daemons with persistent state in
the past, and they don't in this PR either. But I thought it was
important to make the change before we support plugins as daemons, as an
exclusive mutable reference is not compatible with parallel plugin
calls.
I suggest this gets merged sometime *after* the current pending release,
so that we have some time to adjust to the previous plugin protocol
changes that don't require code changes before making ones that do.
# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`
# After Submitting
I will document the additional protocol features (`EngineCall`,
`EngineCallResponse`), and constraints on plugin call processing if
engine calls are used - basically, to be aware that an engine call could
result in a nested plugin call, so the plugin should be able to handle
that.
# Description
Replace panics with errors in thread spawning.
Also adds `IntoSpanned` trait for easily constructing `Spanned`, and an
implementation of `From<Spanned<std::io::Error>>` for `ShellError`,
which is used to provide context for the error wherever there was a span
conveniently available. In general this should make it more convenient
to do the right thing with `std::io::Error` and always add a span to it
when it's possible to do so.
# User-Facing Changes
Fewer panics!
# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`
