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use nu_protocol::{
Example, IntoSpanned, LabeledError, PipelineData, PluginExample, PluginSignature, ShellError,
Signature, Value,
};
use crate::{EngineInterface, EvaluatedCall, Plugin};
/// The API for a Nushell plugin command
///
/// This is the trait that Nushell plugin commands must implement. The methods defined on
/// `PluginCommand` are invoked by [`serve_plugin`](crate::serve_plugin) during plugin registration
/// and execution.
///
/// The plugin command must be able to be safely shared between threads, so that multiple
/// invocations can be run in parallel. If interior mutability is desired, consider synchronization
/// primitives such as [mutexes](std::sync::Mutex) and [channels](std::sync::mpsc).
///
/// This version of the trait expects stream input and output. If you have a simple plugin that just
/// operates on plain values, consider using [`SimplePluginCommand`] instead.
///
/// # Examples
/// Basic usage:
/// ```
/// # use nu_plugin::*;
/// # use nu_protocol::{Signature, PipelineData, Type, Value, LabeledError};
/// struct LowercasePlugin;
/// struct Lowercase;
///
/// impl PluginCommand for Lowercase {
/// type Plugin = LowercasePlugin;
///
/// fn name(&self) -> &str {
/// "lowercase"
/// }
///
/// fn usage(&self) -> &str {
/// "Convert each string in a stream to lowercase"
/// }
///
/// fn signature(&self) -> Signature {
/// Signature::build(PluginCommand::name(self))
/// .input_output_type(Type::List(Type::String.into()), Type::List(Type::String.into()))
/// }
///
/// fn run(
/// &self,
/// plugin: &LowercasePlugin,
/// engine: &EngineInterface,
/// call: &EvaluatedCall,
/// input: PipelineData,
/// ) -> Result<PipelineData, LabeledError> {
/// let span = call.head;
/// Ok(input.map(move |value| {
/// value.as_str()
/// .map(|string| Value::string(string.to_lowercase(), span))
/// // Errors in a stream should be returned as values.
/// .unwrap_or_else(|err| Value::error(err, span))
/// }, None)?)
/// }
/// }
///
/// # impl Plugin for LowercasePlugin {
/// # fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin=Self>>> {
/// # vec![Box::new(Lowercase)]
/// # }
/// # }
/// #
/// # fn main() {
/// # serve_plugin(&LowercasePlugin{}, MsgPackSerializer)
/// # }
/// ```
pub trait PluginCommand: Sync {
/// The type of plugin this command runs on.
///
/// Since [`.run()`] takes a reference to the plugin, it is necessary to define the type of
/// plugin that the command expects here.
type Plugin: Plugin;
/// The name of the command from within Nu.
///
/// In case this contains spaces, it will be treated as a subcommand.
fn name(&self) -> &str;
/// The signature of the command.
///
/// This defines the arguments and input/output types of the command.
fn signature(&self) -> Signature;
/// A brief description of usage for the command.
///
/// This should be short enough to fit in completion menus.
fn usage(&self) -> &str;
/// Additional documentation for usage of the command.
///
/// This is optional - any arguments documented by [`.signature()`] will be shown in the help
/// page automatically. However, this can be useful for explaining things that would be too
/// brief to include in [`.usage()`] and may span multiple lines.
fn extra_usage(&self) -> &str {
""
}
/// Search terms to help users find the command.
///
/// A search query matching any of these search keywords, e.g. on `help --find`, will also
/// show this command as a result. This may be used to suggest this command as a replacement
/// for common system commands, or based alternate names for the functionality this command
/// provides.
///
/// For example, a `fold` command might mention `reduce` in its search terms.
fn search_terms(&self) -> Vec<&str> {
vec![]
}
/// Examples, in Nu, of how the command might be used.
///
/// The examples are not restricted to only including this command, and may demonstrate
/// pipelines using the command. A `result` may optionally be provided to show users what the
/// command would return.
///
/// `PluginTest::test_command_examples()` from the
/// [`nu-plugin-test-support`](https://docs.rs/nu-plugin-test-support) crate can be used in
/// plugin tests to automatically test that examples produce the `result`s as specified.
fn examples(&self) -> Vec<Example> {
vec![]
}
/// Perform the actual behavior of the plugin command.
///
/// The behavior of the plugin is defined by the implementation of this method. When Nushell
/// invoked the plugin [`serve_plugin`](crate::serve_plugin) will call this method and print the
/// serialized returned value or error to stdout, which Nushell will interpret.
///
/// `engine` provides an interface back to the Nushell engine. See [`EngineInterface`] docs for
/// details on what methods are available.
///
/// The `call` contains metadata describing how the plugin command was invoked, including
/// arguments, and `input` contains the structured data piped into the command.
///
/// This variant expects to receive and produce [`PipelineData`], which allows for stream-based
/// handling of I/O. This is recommended if the plugin is expected to transform large
/// lists or potentially large quantities of bytes. The API is more complex however, and
/// [`SimplePluginCommand`] is recommended instead if this is not a concern.
fn run(
&self,
plugin: &Self::Plugin,
engine: &EngineInterface,
call: &EvaluatedCall,
input: PipelineData,
) -> Result<PipelineData, LabeledError>;
}
/// The API for a simple Nushell plugin command
///
/// This trait is an alternative to [`PluginCommand`], and operates on values instead of streams.
/// Note that this may make handling large lists more difficult.
///
/// The plugin command must be able to be safely shared between threads, so that multiple
/// invocations can be run in parallel. If interior mutability is desired, consider synchronization
/// primitives such as [mutexes](std::sync::Mutex) and [channels](std::sync::mpsc).
///
/// # Examples
/// Basic usage:
/// ```
/// # use nu_plugin::*;
/// # use nu_protocol::{LabeledError, Signature, Type, Value};
/// struct HelloPlugin;
/// struct Hello;
///
/// impl SimplePluginCommand for Hello {
/// type Plugin = HelloPlugin;
///
/// fn name(&self) -> &str {
/// "hello"
/// }
///
/// fn usage(&self) -> &str {
/// "Every programmer's favorite greeting"
/// }
///
/// fn signature(&self) -> Signature {
/// Signature::build(PluginCommand::name(self))
/// .input_output_type(Type::Nothing, Type::String)
/// }
///
/// fn run(
/// &self,
/// plugin: &HelloPlugin,
/// engine: &EngineInterface,
/// call: &EvaluatedCall,
/// input: &Value,
/// ) -> Result<Value, LabeledError> {
/// Ok(Value::string("Hello, World!".to_owned(), call.head))
/// }
/// }
///
/// # impl Plugin for HelloPlugin {
/// # fn commands(&self) -> Vec<Box<dyn PluginCommand<Plugin=Self>>> {
/// # vec![Box::new(Hello)]
/// # }
/// # }
/// #
/// # fn main() {
/// # serve_plugin(&HelloPlugin{}, MsgPackSerializer)
/// # }
/// ```
pub trait SimplePluginCommand: Sync {
/// The type of plugin this command runs on.
///
/// Since [`.run()`] takes a reference to the plugin, it is necessary to define the type of
/// plugin that the command expects here.
type Plugin: Plugin;
/// The name of the command from within Nu.
///
/// In case this contains spaces, it will be treated as a subcommand.
fn name(&self) -> &str;
/// The signature of the command.
///
/// This defines the arguments and input/output types of the command.
fn signature(&self) -> Signature;
/// A brief description of usage for the command.
///
/// This should be short enough to fit in completion menus.
fn usage(&self) -> &str;
/// Additional documentation for usage of the command.
///
/// This is optional - any arguments documented by [`.signature()`] will be shown in the help
/// page automatically. However, this can be useful for explaining things that would be too
/// brief to include in [`.usage()`] and may span multiple lines.
fn extra_usage(&self) -> &str {
""
}
/// Search terms to help users find the command.
///
/// A search query matching any of these search keywords, e.g. on `help --find`, will also
/// show this command as a result. This may be used to suggest this command as a replacement
/// for common system commands, or based alternate names for the functionality this command
/// provides.
///
/// For example, a `fold` command might mention `reduce` in its search terms.
fn search_terms(&self) -> Vec<&str> {
vec![]
}
/// Examples, in Nu, of how the command might be used.
///
/// The examples are not restricted to only including this command, and may demonstrate
/// pipelines using the command. A `result` may optionally be provided to show users what the
/// command would return.
///
/// `PluginTest::test_command_examples()` from the
/// [`nu-plugin-test-support`](https://docs.rs/nu-plugin-test-support) crate can be used in
/// plugin tests to automatically test that examples produce the `result`s as specified.
fn examples(&self) -> Vec<Example> {
vec![]
}
/// Perform the actual behavior of the plugin command.
///
/// The behavior of the plugin is defined by the implementation of this method. When Nushell
/// invoked the plugin [`serve_plugin`](crate::serve_plugin) will call this method and print the
/// serialized returned value or error to stdout, which Nushell will interpret.
///
/// `engine` provides an interface back to the Nushell engine. See [`EngineInterface`] docs for
/// details on what methods are available.
///
/// The `call` contains metadata describing how the plugin command was invoked, including
/// arguments, and `input` contains the structured data piped into the command.
///
/// This variant does not support streaming. Consider implementing [`PluginCommand`] directly
/// if streaming is desired.
fn run(
&self,
plugin: &Self::Plugin,
engine: &EngineInterface,
call: &EvaluatedCall,
input: &Value,
) -> Result<Value, LabeledError>;
}
/// All [`SimplePluginCommand`]s can be used as [`PluginCommand`]s, but input streams will be fully
/// consumed before the plugin command runs.
impl<T> PluginCommand for T
where
T: SimplePluginCommand,
{
type Plugin = <Self as SimplePluginCommand>::Plugin;
fn examples(&self) -> Vec<Example> {
<Self as SimplePluginCommand>::examples(self)
}
fn extra_usage(&self) -> &str {
<Self as SimplePluginCommand>::extra_usage(self)
}
fn name(&self) -> &str {
<Self as SimplePluginCommand>::name(self)
}
fn run(
&self,
plugin: &Self::Plugin,
engine: &EngineInterface,
call: &EvaluatedCall,
input: PipelineData,
) -> Result<PipelineData, LabeledError> {
// Unwrap the PipelineData from input, consuming the potential stream, and pass it to the
// simpler signature in Plugin
let span = input.span().unwrap_or(call.head);
let input_value = input.into_value(span);
// Wrap the output in PipelineData::Value
<Self as SimplePluginCommand>::run(self, plugin, engine, call, &input_value)
.map(|value| PipelineData::Value(value, None))
}
fn search_terms(&self) -> Vec<&str> {
<Self as SimplePluginCommand>::search_terms(self)
}
fn signature(&self) -> Signature {
<Self as SimplePluginCommand>::signature(self)
}
fn usage(&self) -> &str {
<Self as SimplePluginCommand>::usage(self)
}
}
/// Build a [`PluginSignature`] from the signature-related methods on [`PluginCommand`].
///
/// This is sent to the engine on `register`.
///
/// This is not a public API.
#[doc(hidden)]
pub fn create_plugin_signature(command: &(impl PluginCommand + ?Sized)) -> PluginSignature {
PluginSignature::new(
// Add results of trait methods to signature
command
.signature()
.usage(command.usage())
.extra_usage(command.extra_usage())
.search_terms(
command
.search_terms()
.into_iter()
.map(String::from)
.collect(),
),
// Convert `Example`s to `PluginExample`s
command
.examples()
.into_iter()
.map(PluginExample::from)
.collect(),
)
}
/// Render examples to their base value so they can be sent in the response to `Signature`.
pub(crate) fn render_examples(
plugin: &impl Plugin,
engine: &EngineInterface,
examples: &mut [PluginExample],
) -> Result<(), ShellError> {
for example in examples {
if let Some(ref mut value) = example.result {
value.recurse_mut(&mut |value| {
let span = value.span();
match value {
Value::Custom { .. } => {
let value_taken = std::mem::replace(value, Value::nothing(span));
let Value::Custom { val, .. } = value_taken else {
unreachable!()
};
*value =
plugin.custom_value_to_base_value(engine, val.into_spanned(span))?;
Ok::<_, ShellError>(())
}
// Collect LazyRecord before proceeding
Value::LazyRecord { ref val, .. } => {
*value = val.collect()?;
Ok(())
}
_ => Ok(()),
}
})?;
}
}
Ok(())
}