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//! Module implementing custom syntax for [`Engine`].
#![cfg(not(feature = "no_custom_syntax"))]
use crate::ast::Expr;
use crate::func::SendSync;
use crate::parser::ParseResult;
use crate::tokenizer::{is_reserved_keyword_or_symbol, is_valid_identifier, Token};
use crate::types::dynamic::Variant;
use crate::{
Dynamic, Engine, EvalContext, Identifier, ImmutableString, LexError, Position, RhaiResult,
};
#[cfg(feature = "no_std")]
use std::prelude::v1::*;
use std::{borrow::Borrow, ops::Deref};
/// Collection of special markers for custom syntax definition.
pub mod markers {
/// Special marker for matching an expression.
pub const CUSTOM_SYNTAX_MARKER_EXPR: &str = "$expr$";
/// Special marker for matching a statements block.
pub const CUSTOM_SYNTAX_MARKER_BLOCK: &str = "$block$";
/// Special marker for matching an identifier.
pub const CUSTOM_SYNTAX_MARKER_IDENT: &str = "$ident$";
/// Special marker for matching a single symbol.
pub const CUSTOM_SYNTAX_MARKER_SYMBOL: &str = "$symbol$";
/// Special marker for matching a string literal.
pub const CUSTOM_SYNTAX_MARKER_STRING: &str = "$string$";
/// Special marker for matching an integer number.
pub const CUSTOM_SYNTAX_MARKER_INT: &str = "$int$";
/// Special marker for matching a floating-point number.
#[cfg(not(feature = "no_float"))]
pub const CUSTOM_SYNTAX_MARKER_FLOAT: &str = "$float$";
/// Special marker for matching a boolean value.
pub const CUSTOM_SYNTAX_MARKER_BOOL: &str = "$bool$";
/// Special marker for identifying the custom syntax variant.
pub const CUSTOM_SYNTAX_MARKER_SYNTAX_VARIANT: &str = "$$";
}
/// A general expression evaluation trait object.
#[cfg(not(feature = "sync"))]
pub type FnCustomSyntaxEval = dyn Fn(&mut EvalContext, &[Expression], &Dynamic) -> RhaiResult;
/// A general expression evaluation trait object.
#[cfg(feature = "sync")]
pub type FnCustomSyntaxEval =
dyn Fn(&mut EvalContext, &[Expression], &Dynamic) -> RhaiResult + Send + Sync;
/// A general expression parsing trait object.
#[cfg(not(feature = "sync"))]
pub type FnCustomSyntaxParse =
dyn Fn(&[ImmutableString], &str, &mut Dynamic) -> ParseResult<Option<ImmutableString>>;
/// A general expression parsing trait object.
#[cfg(feature = "sync")]
pub type FnCustomSyntaxParse = dyn Fn(&[ImmutableString], &str, &mut Dynamic) -> ParseResult<Option<ImmutableString>>
+ Send
+ Sync;
/// An expression sub-tree in an [`AST`][crate::AST].
#[derive(Debug, Clone)]
pub struct Expression<'a>(&'a Expr);
impl<'a> From<&'a Expr> for Expression<'a> {
#[inline(always)]
fn from(expr: &'a Expr) -> Self {
Self(expr)
}
}
impl Expression<'_> {
/// Evaluate this [expression tree][Expression] within an [evaluation context][`EvalContext`].
///
/// # WARNING - Low Level API
///
/// This function is very low level. It evaluates an expression from an [`AST`][crate::AST].
#[inline(always)]
pub fn eval_with_context(&self, context: &mut EvalContext) -> RhaiResult {
context.eval_expression_tree(self)
}
/// Evaluate this [expression tree][Expression] within an [evaluation context][`EvalContext`].
///
/// The following option is available:
///
/// * whether to rewind the [`Scope`][crate::Scope] after evaluation if the expression is a [`StmtBlock`][crate::ast::StmtBlock]
///
/// # WARNING - Unstable API
///
/// This API is volatile and may change in the future.
///
/// # WARNING - Low Level API
///
/// This function is _extremely_ low level. It evaluates an expression from an [`AST`][crate::AST].
#[deprecated = "This API is NOT deprecated, but it is considered volatile and may change in the future."]
#[inline(always)]
pub fn eval_with_context_raw(
&self,
context: &mut EvalContext,
rewind_scope: bool,
) -> RhaiResult {
#[allow(deprecated)]
context.eval_expression_tree_raw(self, rewind_scope)
}
/// Get the value of this expression if it is a variable name or a string constant.
///
/// Returns [`None`] also if the constant is not of the specified type.
#[inline(always)]
#[must_use]
pub fn get_string_value(&self) -> Option<&str> {
match self.0 {
#[cfg(not(feature = "no_module"))]
Expr::Variable(x, ..) if !x.1.is_empty() => None,
Expr::Variable(x, ..) => Some(x.3.as_str()),
#[cfg(not(feature = "no_function"))]
Expr::ThisPtr(..) => Some(crate::engine::KEYWORD_THIS),
Expr::StringConstant(x, ..) => Some(x.as_str()),
_ => None,
}
}
/// Get the position of this expression.
#[inline(always)]
#[must_use]
pub const fn position(&self) -> Position {
self.0.position()
}
/// Get the value of this expression if it is a literal constant.
///
/// Supports [`INT`][crate::INT], [`FLOAT`][crate::FLOAT], `()`, `char`, `bool` and
/// [`ImmutableString`][crate::ImmutableString].
///
/// Returns [`None`] also if the constant is not of the specified type.
#[inline]
#[must_use]
pub fn get_literal_value<T: Variant>(&self) -> Option<T> {
// Coded this way in order to maximally leverage potentials for dead-code removal.
match self.0 {
Expr::IntegerConstant(x, ..) => reify! { *x => Option<T> },
#[cfg(not(feature = "no_float"))]
Expr::FloatConstant(x, ..) => reify! { *x => Option<T> },
Expr::CharConstant(x, ..) => reify! { *x => Option<T> },
Expr::StringConstant(x, ..) => reify! { x.clone() => Option<T> },
Expr::Variable(x, ..) => reify! { x.3.clone() => Option<T> },
Expr::BoolConstant(x, ..) => reify! { *x => Option<T> },
Expr::Unit(..) => reify! { () => Option<T> },
_ => None,
}
}
}
impl Borrow<Expr> for Expression<'_> {
#[inline(always)]
#[must_use]
fn borrow(&self) -> &Expr {
self.0
}
}
impl AsRef<Expr> for Expression<'_> {
#[inline(always)]
#[must_use]
fn as_ref(&self) -> &Expr {
self.0
}
}
impl Deref for Expression<'_> {
type Target = Expr;
#[inline(always)]
#[must_use]
fn deref(&self) -> &Self::Target {
self.0
}
}
/// Definition of a custom syntax definition.
pub struct CustomSyntax {
/// A parsing function to return the next token in a custom syntax based on the
/// symbols parsed so far.
pub parse: Box<FnCustomSyntaxParse>,
/// Custom syntax implementation function.
pub func: Box<FnCustomSyntaxEval>,
/// Any variables added/removed in the scope?
pub scope_may_be_changed: bool,
}
impl Engine {
/// Register a custom syntax with the [`Engine`].
///
/// Not available under `no_custom_syntax`.
///
/// * `symbols` holds a slice of strings that define the custom syntax.
/// * `scope_may_be_changed` specifies variables _may_ be added/removed by this custom syntax.
/// * `func` is the implementation function.
///
/// ## Note on `symbols`
///
/// * Whitespaces around symbols are stripped.
/// * Symbols that are all-whitespace or empty are ignored.
/// * If `symbols` does not contain at least one valid token, then the custom syntax registration
/// is simply ignored.
///
/// ## Note on `scope_may_be_changed`
///
/// If `scope_may_be_changed` is `true`, then _size_ of the current [`Scope`][crate::Scope]
/// _may_ be modified by this custom syntax.
///
/// Adding new variables and/or removing variables count.
///
/// Simply modifying the values of existing variables does NOT count, as the _size_ of the
/// current [`Scope`][crate::Scope] is unchanged, so `false` should be passed.
///
/// Replacing one variable with another (i.e. adding a new variable and removing one variable at
/// the same time so that the total _size_ of the [`Scope`][crate::Scope] is unchanged) also
/// does NOT count, so `false` should be passed.
pub fn register_custom_syntax<S: AsRef<str> + Into<Identifier>>(
&mut self,
symbols: impl AsRef<[S]>,
scope_may_be_changed: bool,
func: impl Fn(&mut EvalContext, &[Expression]) -> RhaiResult + SendSync + 'static,
) -> ParseResult<&mut Self> {
#[allow(clippy::wildcard_imports)]
use markers::*;
let mut segments = Vec::<ImmutableString>::new();
for s in symbols.as_ref() {
let s = s.as_ref().trim();
// Skip empty symbols
if s.is_empty() {
continue;
}
let token = Token::lookup_symbol_from_syntax(s).or_else(|| {
is_reserved_keyword_or_symbol(s)
.0
.then(|| Token::Reserved(Box::new(s.into())))
});
let seg = match s {
// Markers not in first position
CUSTOM_SYNTAX_MARKER_IDENT
| CUSTOM_SYNTAX_MARKER_SYMBOL
| CUSTOM_SYNTAX_MARKER_EXPR
| CUSTOM_SYNTAX_MARKER_BLOCK
| CUSTOM_SYNTAX_MARKER_BOOL
| CUSTOM_SYNTAX_MARKER_INT
| CUSTOM_SYNTAX_MARKER_STRING
if !segments.is_empty() =>
{
s.into()
}
// Markers not in first position
#[cfg(not(feature = "no_float"))]
CUSTOM_SYNTAX_MARKER_FLOAT if !segments.is_empty() => s.into(),
// Identifier not in first position
_ if !segments.is_empty() && is_valid_identifier(s) => s.into(),
// Keyword/symbol not in first position
_ if !segments.is_empty() && token.is_some() => {
// Make it a custom keyword/symbol if it is disabled or reserved
if (self.is_symbol_disabled(s)
|| token.as_ref().map_or(false, Token::is_reserved))
&& !self.is_custom_keyword(s)
{
self.custom_keywords.insert(s.into(), None);
}
s.into()
}
// Standard keyword in first position but not disabled
_ if segments.is_empty()
&& token.as_ref().map_or(false, Token::is_standard_keyword)
&& !self.is_symbol_disabled(s) =>
{
return Err(LexError::ImproperSymbol(
s.to_string(),
format!("Improper symbol for custom syntax at position #0: '{s}'"),
)
.into_err(Position::NONE));
}
// Identifier or symbol in first position
_ if segments.is_empty()
&& (is_valid_identifier(s) || is_reserved_keyword_or_symbol(s).0) =>
{
// Make it a custom keyword/symbol if it is disabled or reserved
if self.is_symbol_disabled(s)
|| (token.as_ref().map_or(false, Token::is_reserved)
&& !self.is_custom_keyword(s))
{
self.custom_keywords.insert(s.into(), None);
}
s.into()
}
// Anything else is an error
_ => {
return Err(LexError::ImproperSymbol(
s.to_string(),
format!(
"Improper symbol for custom syntax at position #{}: '{s}'",
segments.len() + 1,
),
)
.into_err(Position::NONE));
}
};
segments.push(seg);
}
// If the syntax has nothing, just ignore the registration
if segments.is_empty() {
return Ok(self);
}
// The first keyword/symbol is the discriminator
let key = segments[0].clone();
self.register_custom_syntax_with_state_raw(
key,
// Construct the parsing function
move |stream, _, _| match stream.len() {
len if len >= segments.len() => Ok(None),
len => Ok(Some(segments[len].clone())),
},
scope_may_be_changed,
move |context, expressions, _| func(context, expressions),
);
Ok(self)
}
/// Register a custom syntax with the [`Engine`] with custom user-defined state.
///
/// Not available under `no_custom_syntax`.
///
/// # WARNING - Low Level API
///
/// This function is very low level.
///
/// * `scope_may_be_changed` specifies variables have been added/removed by this custom syntax.
/// * `parse` is the parsing function.
/// * `func` is the implementation function.
///
/// All custom keywords used as symbols must be manually registered via [`Engine::register_custom_operator`].
/// Otherwise, they won't be recognized.
///
/// # Parsing Function Signature
///
/// The parsing function has the following signature:
///
/// `Fn(symbols: &[ImmutableString], look_ahead: &str, state: &mut Dynamic) -> Result<Option<ImmutableString>, ParseError>`
///
/// where:
/// * `symbols`: a slice of symbols that have been parsed so far, possibly containing `$expr$` and/or `$block$`;
/// `$ident$` and other literal markers are replaced by the actual text
/// * `look_ahead`: a string slice containing the next symbol that is about to be read
/// * `state`: a [`Dynamic`] value that contains a user-defined state
///
/// ## Return value
///
/// * `Ok(None)`: parsing complete and there are no more symbols to match.
/// * `Ok(Some(symbol))`: the next symbol to match, which can also be `$expr$`, `$ident$` or `$block$`.
/// * `Err(ParseError)`: error that is reflected back to the [`Engine`], normally `ParseError(ParseErrorType::BadInput(LexError::ImproperSymbol(message)), Position::NONE)` to indicate a syntax error, but it can be any [`ParseError`][crate::ParseError].
pub fn register_custom_syntax_with_state_raw(
&mut self,
key: impl Into<Identifier>,
parse: impl Fn(&[ImmutableString], &str, &mut Dynamic) -> ParseResult<Option<ImmutableString>>
+ SendSync
+ 'static,
scope_may_be_changed: bool,
func: impl Fn(&mut EvalContext, &[Expression], &Dynamic) -> RhaiResult + SendSync + 'static,
) -> &mut Self {
self.custom_syntax.insert(
key.into(),
CustomSyntax {
parse: Box::new(parse),
func: Box::new(func),
scope_may_be_changed,
}
.into(),
);
self
}
}