243 lines
8.5 KiB
Rust
243 lines
8.5 KiB
Rust
//! Module implementing custom syntax for [`Engine`].
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use crate::ast::Expr;
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use crate::engine::EvalContext;
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use crate::fn_native::SendSync;
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use crate::token::{is_valid_identifier, Token};
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use crate::{
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Engine, Identifier, ImmutableString, LexError, ParseError, Position, RhaiResult, Shared,
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StaticVec,
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};
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#[cfg(feature = "no_std")]
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use std::prelude::v1::*;
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pub const MARKER_EXPR: &str = "$expr$";
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pub const MARKER_BLOCK: &str = "$block$";
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pub const MARKER_IDENT: &str = "$ident$";
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/// A general expression evaluation trait object.
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#[cfg(not(feature = "sync"))]
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pub type FnCustomSyntaxEval = dyn Fn(&mut EvalContext, &[Expression]) -> RhaiResult;
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/// A general expression evaluation trait object.
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#[cfg(feature = "sync")]
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pub type FnCustomSyntaxEval = dyn Fn(&mut EvalContext, &[Expression]) -> RhaiResult + Send + Sync;
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/// A general expression parsing trait object.
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#[cfg(not(feature = "sync"))]
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pub type FnCustomSyntaxParse =
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dyn Fn(&[ImmutableString], &str) -> Result<Option<ImmutableString>, ParseError>;
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/// A general expression parsing trait object.
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#[cfg(feature = "sync")]
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pub type FnCustomSyntaxParse =
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dyn Fn(&[ImmutableString], &str) -> Result<Option<ImmutableString>, ParseError> + Send + Sync;
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/// An expression sub-tree in an [`AST`][crate::AST].
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#[derive(Debug, Clone)]
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pub struct Expression<'a>(&'a Expr);
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impl<'a> From<&'a Expr> for Expression<'a> {
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#[inline(always)]
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fn from(expr: &'a Expr) -> Self {
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Self(expr)
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}
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}
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impl Expression<'_> {
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/// If this expression is a variable name, return it. Otherwise [`None`].
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#[inline(always)]
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pub fn get_variable_name(&self) -> Option<&str> {
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self.0.get_variable_name(true)
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}
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/// Get the expression.
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#[inline(always)]
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pub(crate) fn expr(&self) -> &Expr {
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&self.0
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}
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/// Get the position of this expression.
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#[inline(always)]
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pub fn position(&self) -> Position {
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self.0.position()
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}
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}
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impl EvalContext<'_, '_, '_, '_, '_, '_, '_> {
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/// Evaluate an [expression tree][Expression].
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///
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/// # WARNING - Low Level API
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///
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/// This function is very low level. It evaluates an expression from an [`AST`][crate::AST].
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#[inline(always)]
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pub fn eval_expression_tree(&mut self, expr: &Expression) -> RhaiResult {
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self.engine.eval_expr(
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self.scope,
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self.mods,
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self.state,
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self.lib,
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self.this_ptr,
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expr.expr(),
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self.level,
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)
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}
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}
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/// Definition of a custom syntax definition.
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pub struct CustomSyntax {
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/// A parsing function to return the next keyword in a custom syntax based on the
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/// keywords parsed so far.
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pub parse: Box<FnCustomSyntaxParse>,
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/// Custom syntax implementation function.
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pub func: Shared<FnCustomSyntaxEval>,
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/// Delta number of variables in the scope.
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pub scope_delta: isize,
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}
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impl Engine {
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/// Register a custom syntax with the [`Engine`].
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///
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/// * `keywords` holds a slice of strings that define the custom syntax.
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/// * `new_vars` is the number of new variables declared by this custom syntax, or the number of variables removed (if negative).
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/// * `func` is the implementation function.
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///
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/// # Notes
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///
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/// If `new_vars` is positive, then a number of new variables are expected to be pushed into the
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/// current [`Scope`][crate::Scope].
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///
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/// If `new_vars` is negative, then it is expected that only the top `new_vars` variables in the
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/// current [`Scope`][crate::Scope] will be _popped_. Do not randomly remove variables.
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pub fn register_custom_syntax<S: AsRef<str> + Into<Identifier>>(
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&mut self,
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keywords: &[S],
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new_vars: isize,
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func: impl Fn(&mut EvalContext, &[Expression]) -> RhaiResult + SendSync + 'static,
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) -> Result<&mut Self, ParseError> {
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let keywords = keywords.as_ref();
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let mut segments: StaticVec<ImmutableString> = Default::default();
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for s in keywords {
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let s = s.as_ref().trim();
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// skip empty keywords
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if s.is_empty() {
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continue;
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}
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let token = Token::lookup_from_syntax(s);
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let seg = match s {
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// Markers not in first position
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MARKER_IDENT | MARKER_EXPR | MARKER_BLOCK if !segments.is_empty() => s.into(),
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// Standard or reserved keyword/symbol not in first position
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s if !segments.is_empty() && token.is_some() => {
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// Make it a custom keyword/symbol if it is disabled or reserved
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if (self.disabled_symbols.contains(s)
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|| matches!(token, Some(Token::Reserved(_))))
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&& !self.custom_keywords.contains_key(s)
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{
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self.custom_keywords.insert(s.into(), None);
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}
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s.into()
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}
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// Standard keyword in first position
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s if segments.is_empty()
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&& token
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.as_ref()
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.map_or(false, |v| v.is_keyword() || v.is_reserved()) =>
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{
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return Err(LexError::ImproperSymbol(
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s.to_string(),
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format!(
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"Improper symbol for custom syntax at position #{}: '{}'",
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segments.len() + 1,
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s
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),
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)
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.into_err(Position::NONE)
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.into());
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}
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// Identifier in first position
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s if segments.is_empty() && is_valid_identifier(s.chars()) => {
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// Make it a custom keyword/symbol if it is disabled or reserved
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if (self.disabled_symbols.contains(s)
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|| matches!(token, Some(Token::Reserved(_))))
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&& !self.custom_keywords.contains_key(s)
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{
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self.custom_keywords.insert(s.into(), None);
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}
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s.into()
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}
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// Anything else is an error
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_ => {
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return Err(LexError::ImproperSymbol(
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s.to_string(),
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format!(
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"Improper symbol for custom syntax at position #{}: '{}'",
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segments.len() + 1,
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s
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),
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)
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.into_err(Position::NONE)
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.into());
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}
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};
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segments.push(seg);
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}
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// If the syntax has no keywords, just ignore the registration
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if segments.is_empty() {
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return Ok(self);
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}
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// The first keyword is the discriminator
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let key = segments[0].clone();
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self.register_custom_syntax_raw(
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key,
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// Construct the parsing function
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move |stream, _| {
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if stream.len() >= segments.len() {
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Ok(None)
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} else {
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Ok(Some(segments[stream.len()].clone()))
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}
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},
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new_vars,
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func,
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);
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Ok(self)
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}
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/// Register a custom syntax with the [`Engine`].
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///
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/// # WARNING - Low Level API
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///
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/// This function is very low level.
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///
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/// * `new_vars` is the number of new variables declared by this custom syntax, or the number of variables removed (if negative).
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/// * `parse` is the parsing function.
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/// * `func` is the implementation function.
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///
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/// All custom keywords must be manually registered via [`Engine::register_custom_operator`].
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/// Otherwise, custom keywords won't be recognized.
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pub fn register_custom_syntax_raw(
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&mut self,
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key: impl Into<Identifier>,
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parse: impl Fn(&[ImmutableString], &str) -> Result<Option<ImmutableString>, ParseError>
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+ SendSync
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+ 'static,
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new_vars: isize,
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func: impl Fn(&mut EvalContext, &[Expression]) -> RhaiResult + SendSync + 'static,
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) -> &mut Self {
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let syntax = CustomSyntax {
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parse: Box::new(parse),
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func: (Box::new(func) as Box<FnCustomSyntaxEval>).into(),
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scope_delta: new_vars,
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};
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self.custom_syntax.insert(key.into(), syntax);
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self
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}
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}
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