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Add variable definition filter.

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This commit is contained in:
Stephen Chung 2022-02-04 22:59:41 +08:00
parent 936dc01e39
commit be9356727f
6 changed files with 173 additions and 43 deletions
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1
CHANGELOG.md
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@ -27,6 +27,7 @@ New features
* A new bin tool, `rhai-dbg` (aka _The Rhai Debugger_), is added to showcase the debugging interface.
* A new package, `DebuggingPackage`, is added which contains the `back_trace` function to get the current call stack anywhere in a script.
* `Engine::set_allow_shadowing` is added to allow/disallow variables _shadowing_, with new errors `EvalAltResult::ErrorVariableExists` and `ParseErrorType::VariableExists`.
* `Engine::on_def_var` allows registering a closure which can decide whether a variable definition is allow to continue, or should fail with an error.
Enhancements
------------

63
src/api/events.rs
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@ -15,12 +15,12 @@ impl Engine {
/// > `Fn(name: &str, index: usize, context: &EvalContext) -> Result<Option<Dynamic>, Box<EvalAltResult>>`
///
/// where:
/// * `name`: name of the variable.
/// * `index`: an offset from the bottom of the current [`Scope`][crate::Scope] that the
/// variable is supposed to reside. Offsets start from 1, with 1 meaning the last variable in
/// the current [`Scope`][crate::Scope]. Essentially the correct variable is at position
/// `scope.len() - index`. If `index` is zero, then there is no pre-calculated offset position
/// and a search through the current [`Scope`][crate::Scope] must be performed.
///
/// * `context`: the current [evaluation context][`EvalContext`].
///
/// ## Return value
@ -63,6 +63,67 @@ impl Engine {
self.resolve_var = Some(Box::new(callback));
self
}
/// Provide a callback that will be invoked before the definition of each variable .
///
/// # Callback Function Signature
///
/// The callback function signature takes the following form:
///
/// > `Fn(name: &str, is_const: bool, block_level: usize, will_shadow: bool, context: &EvalContext) -> Result<bool, Box<EvalAltResult>>`
///
/// where:
/// * `name`: name of the variable to be defined.
/// * `is_const`: `true` if the statement is `const`, otherwise it is `let`.
/// * `block_level`: the current nesting level of statement blocks, with zero being the global level
/// * `will_shadow`: will the variable _shadow_ an existing variable?
/// * `context`: the current [evaluation context][`EvalContext`].
///
/// ## Return value
///
/// * `Ok(true)`: continue with normal variable definition.
/// * `Ok(false)`: deny the variable definition with an [runtime error][EvalAltResult::ErrorRuntime].
///
/// ## Raising errors
///
/// Return `Err(...)` if there is an error.
///
/// # Example
///
/// ```should_panic
/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
/// use rhai::Engine;
///
/// let mut engine = Engine::new();
///
/// // Register a variable definition filter.
/// engine.on_def_var(|name, is_const, _, _, _| {
/// // Disallow defining MYSTIC_NUMBER as a constant
/// if name == "MYSTIC_NUMBER" && is_const {
/// Ok(false)
/// } else {
/// Ok(true)
/// }
/// });
///
/// // The following runs fine:
/// engine.eval::<i64>("let MYSTIC_NUMBER = 42;")?;
///
/// // The following will cause an error:
/// engine.eval::<i64>("const MYSTIC_NUMBER = 42;")?;
///
/// # Ok(())
/// # }
/// ```
#[inline(always)]
pub fn on_def_var(
&mut self,
callback: impl Fn(&str, bool, usize, bool, &EvalContext) -> RhaiResultOf<bool>
+ SendSync
+ 'static,
) -> &mut Self {
self.def_var_filter = Some(Box::new(callback));
self
}
/// _(internals)_ Register a callback that will be invoked during parsing to remap certain tokens.
/// Exported under the `internals` feature only.
///

8
src/engine.rs
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@ -1,7 +1,9 @@
//! Main module defining the script evaluation [`Engine`].
use crate::api::custom_syntax::CustomSyntax;
use crate::func::native::{OnDebugCallback, OnParseTokenCallback, OnPrintCallback, OnVarCallback};
use crate::func::native::{
OnDebugCallback, OnDefVarCallback, OnParseTokenCallback, OnPrintCallback, OnVarCallback,
};
use crate::packages::{Package, StandardPackage};
use crate::tokenizer::Token;
use crate::types::dynamic::Union;
@ -113,6 +115,8 @@ pub struct Engine {
pub(crate) custom_keywords: BTreeMap<Identifier, Option<Precedence>>,
/// Custom syntax.
pub(crate) custom_syntax: BTreeMap<Identifier, Box<CustomSyntax>>,
/// Callback closure for filtering variable definition.
pub(crate) def_var_filter: Option<Box<OnDefVarCallback>>,
/// Callback closure for resolving variable access.
pub(crate) resolve_var: Option<Box<OnVarCallback>>,
/// Callback closure to remap tokens during parsing.
@ -160,6 +164,7 @@ impl fmt::Debug for Engine {
.field("disabled_symbols", &self.disabled_symbols)
.field("custom_keywords", &self.custom_keywords)
.field("custom_syntax", &(!self.custom_syntax.is_empty()))
.field("def_var_filter", &self.def_var_filter.is_some())
.field("resolve_var", &self.resolve_var.is_some())
.field("token_mapper", &self.token_mapper.is_some())
.field("print", &self.print.is_some())
@ -272,6 +277,7 @@ impl Engine {
custom_keywords: BTreeMap::new(),
custom_syntax: BTreeMap::new(),
def_var_filter: None,
resolve_var: None,
token_mapper: None,

43
src/eval/stmt.rs
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@ -1,6 +1,6 @@
//! Module defining functions for evaluating a statement.
use super::{EvalState, GlobalRuntimeState, Target};
use super::{EvalContext, EvalState, GlobalRuntimeState, Target};
use crate::ast::{
BinaryExpr, Expr, Ident, OpAssignment, Stmt, SwitchCases, TryCatchBlock, AST_OPTION_FLAGS::*,
};
@ -240,7 +240,7 @@ impl Engine {
if let Ok(rhs_val) = rhs_result {
let search_result =
self.search_namespace(scope, global, state, lib, this_ptr, lhs);
self.search_namespace(scope, global, state, lib, this_ptr, lhs, level);
if let Ok(search_val) = search_result {
let (mut lhs_ptr, pos) = search_val;
@ -807,7 +807,7 @@ impl Engine {
Err(ERR::ErrorVariableExists(x.name.to_string(), *pos).into())
}
// Let/const statement
Stmt::Var(expr, x, options, _) => {
Stmt::Var(expr, x, options, pos) => {
let var_name = &x.name;
let entry_type = if options.contains(AST_OPTION_CONSTANT) {
@ -817,6 +817,36 @@ impl Engine {
};
let export = options.contains(AST_OPTION_EXPORTED);
let result = if let Some(ref filter) = self.def_var_filter {
let shadowing = scope.contains(var_name);
let scope_level = state.scope_level;
let is_const = entry_type == AccessMode::ReadOnly;
let context = EvalContext {
engine: self,
scope,
global,
state,
lib,
this_ptr,
level: level,
};
match filter(var_name, is_const, scope_level, shadowing, &context) {
Ok(true) => None,
Ok(false) => Some(Err(ERR::ErrorRuntime(
format!("Variable cannot be defined: {}", var_name).into(),
*pos,
)
.into())),
err @ Err(_) => Some(err),
}
} else {
None
};
if let Some(result) = result {
result.map(|_| Dynamic::UNIT)
} else {
let value_result = self
.eval_expr(scope, global, state, lib, this_ptr, expr, level)
.map(Dynamic::flatten);
@ -830,9 +860,9 @@ impl Engine {
&& lib.iter().any(|&m| !m.is_empty())
{
if global.constants.is_none() {
global.constants = Some(crate::Shared::new(crate::Locked::new(
std::collections::BTreeMap::new(),
)));
global.constants = Some(crate::Shared::new(
crate::Locked::new(std::collections::BTreeMap::new()),
));
}
crate::func::locked_write(global.constants.as_ref().unwrap())
.insert(var_name.clone(), value.clone());
@ -861,6 +891,7 @@ impl Engine {
value_result
}
}
}
// Import statement
#[cfg(not(feature = "no_module"))]

8
src/func/native.rs
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@ -444,3 +444,11 @@ pub type OnVarCallback = dyn Fn(&str, usize, &EvalContext) -> RhaiResultOf<Optio
#[cfg(feature = "sync")]
pub type OnVarCallback =
dyn Fn(&str, usize, &EvalContext) -> RhaiResultOf<Option<Dynamic>> + Send + Sync;
/// Callback function for variable definition.
#[cfg(not(feature = "sync"))]
pub type OnDefVarCallback = dyn Fn(&str, bool, usize, bool, &EvalContext) -> RhaiResultOf<bool>;
/// Callback function for variable definition.
#[cfg(feature = "sync")]
pub type OnDefVarCallback =
dyn Fn(&str, bool, usize, bool, &EvalContext) -> RhaiResultOf<bool> + Send + Sync;

23
tests/var_scope.rs
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@ -120,3 +120,26 @@ fn test_var_resolver() -> Result<(), Box<EvalAltResult>> {
Ok(())
}
#[test]
fn test_var_def_filter() -> Result<(), Box<EvalAltResult>> {
let mut engine = Engine::new();
engine.on_def_var(|name, scope_level, _, _| match (name, scope_level) {
("x", 0 | 1) => Ok(false),
_ => Ok(true),
});
assert_eq!(
engine.eval::<INT>("let y = 42; let y = 123; let z = y + 1; z")?,
124
);
assert!(engine.run("let x = 42;").is_err());
assert!(engine.run("const x = 42;").is_err());
assert!(engine.run("let y = 42; { let x = y + 1; }").is_err());
assert!(engine.run("let y = 42; { let x = y + 1; }").is_err());
engine.run("let y = 42; { let z = y + 1; { let x = z + 1; } }")?;
Ok(())
}