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functions.rs
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functions.rs
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//! Global functions and abstractions.
//!
//! This module provides the abstractions for functions that can registered as
//! global functions to the environment via
//! [`add_function`](crate::Environment::add_function).
//!
//! # Using Functions
//!
//! Functions can be called in any place where an expression is valid. They
//! are useful to retrieve data. Some functions are special and provided
//! by the engine (like `super`) within certain context, others are global.
//!
//! The following is a motivating example:
//!
//! ```jinja
//! <pre>{{ debug() }}</pre>
//! ```
//!
//! # Custom Functions
//!
//! A custom global function is just a simple rust function which accepts the
//! [`&State`](crate::State) as first argument, optionally some additional
//! arguments and then returns a result. Global functions are typically used to
//! perform a data loading operation. For instance these functions can be used
//! to expose data to the template that hasn't been provided by the individual
//! render invocation.
//!
//! ```rust
//! # use minijinja::{Environment, State, Error, ErrorKind};
//! # let mut env = Environment::new();
//! fn include_file(_state: &State, name: String) -> Result<String, Error> {
//! std::fs::read_to_string(&name)
//! .map_err(|e| Error::new(
//! ErrorKind::ImpossibleOperation,
//! "cannot load file"
//! ).with_source(e))
//! }
//!
//! env.add_function("include_file", include_file);
//! ```
use std::collections::BTreeMap;
use std::fmt;
use std::sync::Arc;
use crate::error::Error;
use crate::value::{FunctionArgs, Object, Value};
use crate::vm::State;
type FuncFunc = dyn Fn(&State, &[Value]) -> Result<Value, Error> + Sync + Send + 'static;
/// A boxed function.
#[derive(Clone)]
pub(crate) struct BoxedFunction(Arc<FuncFunc>, &'static str);
/// A utility trait that represents global functions.
pub trait Function<Rv, Args>: Send + Sync + 'static {
/// Calls a function with the given arguments.
#[doc(hidden)]
fn invoke(&self, env: &State, args: Args) -> Result<Rv, Error>;
}
macro_rules! tuple_impls {
( $( $name:ident )* ) => {
impl<F, Rv, $($name),*> Function<Rv, ($($name,)*)> for F
where
F: Fn(&State, $($name),*) -> Result<Rv, Error> + Send + Sync + 'static
{
fn invoke(&self, state: &State, args: ($($name,)*)) -> Result<Rv, Error> {
#[allow(non_snake_case)]
let ($($name,)*) = args;
(self)(state, $($name,)*)
}
}
};
}
tuple_impls! {}
tuple_impls! { A }
tuple_impls! { A B }
tuple_impls! { A B C }
tuple_impls! { A B C D }
impl BoxedFunction {
/// Creates a new boxed filter.
pub fn new<F, Rv, Args>(f: F) -> BoxedFunction
where
F: Function<Rv, Args>,
Rv: Into<Value>,
Args: for<'a> FunctionArgs<'a>,
{
BoxedFunction(
Arc::new(move |env, args| -> Result<Value, Error> {
f.invoke(env, FunctionArgs::from_values(args)?)
.map(Into::into)
}),
std::any::type_name::<F>(),
)
}
/// Invokes the function.
pub fn invoke(&self, state: &State, args: &[Value]) -> Result<Value, Error> {
(self.0)(state, args)
}
/// Creates a value from a boxed function.
pub fn to_value(&self) -> Value {
Value::from_object(self.clone())
}
}
impl fmt::Debug for BoxedFunction {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(
f,
"{}",
if self.1.is_empty() {
"BoxedFunction"
} else {
self.1
}
)
}
}
impl fmt::Display for BoxedFunction {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{:?}", self)
}
}
impl Object for BoxedFunction {
fn call(&self, state: &State, args: &[Value]) -> Result<Value, Error> {
self.invoke(state, args)
}
}
pub(crate) fn get_globals() -> BTreeMap<&'static str, Value> {
#[allow(unused_mut)]
let mut rv = BTreeMap::new();
#[cfg(feature = "builtins")]
{
rv.insert("range", BoxedFunction::new(range).to_value());
rv.insert("dict", BoxedFunction::new(dict).to_value());
rv.insert("debug", BoxedFunction::new(debug).to_value());
}
rv
}
#[cfg(feature = "builtins")]
mod builtins {
use super::*;
use crate::error::ErrorKind;
use crate::value::ValueKind;
/// Returns a range.
///
/// Return a list containing an arithmetic progression of integers. `range(i,
/// j)` returns `[i, i+1, i+2, ..., j-1]`. `lower` defaults to 0. When `step` is
/// given, it specifies the increment (or decrement). For example, `range(4)`
/// and `range(0, 4, 1)` return `[0, 1, 2, 3]`. The end point is omitted.
///
/// ```jinja
/// <ul>
/// {% for num in range(1, 11) %}
/// <li>{{ num }}
/// {% endfor %}
/// </ul>
/// ```
#[cfg_attr(docsrs, doc(cfg(feature = "builtins")))]
pub fn range(
_state: &State,
lower: u32,
upper: Option<u32>,
step: Option<u32>,
) -> Result<Vec<u32>, Error> {
let rng = match upper {
Some(upper) => lower..upper,
None => 0..lower,
};
Ok(if let Some(step) = step {
rng.step_by(step as usize).collect()
} else {
rng.collect()
})
}
/// Creates a dictionary.
///
/// This is a convenient alternative for a dictionary literal.
/// `{"foo": "bar"}` is the same as `dict(foo="bar")`.
///
/// ```jinja
/// <script>const CONFIG = {{ dict(
/// DEBUG=true,
/// API_URL_PREFIX="/api"
/// )|tojson }};</script>
/// ```
#[cfg_attr(docsrs, doc(cfg(feature = "builtins")))]
pub fn dict(_state: &State, value: Value) -> Result<Value, Error> {
if value.is_undefined() {
Ok(Value::from(BTreeMap::<bool, Value>::new()))
} else if value.kind() != ValueKind::Map {
Err(Error::from(ErrorKind::ImpossibleOperation))
} else {
Ok(value)
}
}
/// Outputs the current context stringified.
///
/// This is a useful function to quickly figure out the state of affairs
/// in a template. It emits a stringified debug dump of the current
/// engine state including the layers of the context, the current block
/// and auto escaping setting.
///
/// ```jinja
/// <pre>{{ debug() }}</pre>
/// ```
#[cfg_attr(docsrs, doc(cfg(feature = "builtins")))]
pub fn debug(state: &State) -> Result<String, Error> {
Ok(format!("{:#?}", state))
}
}
#[cfg(feature = "builtins")]
pub use self::builtins::*;