rhaj/rhai_engine/rhaibook/engine/options.md

Engine Configuration Options

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A number of other configuration options are available from the [Engine] to fine-tune behavior and safeguards.

Compile-Time Language Features

Method	Description	Default
set_optimization_level (not available under [no_optimize])	sets the amount of script optimizations performed (see [script optimization])	[Simple][OptimizationLevel::Simple]
set_allow_if_expression	allows/disallows if-expressions	allow
set_allow_switch_expression	allows/disallows switch expressions	allow
set_allow_loop_expressions	allows/disallows loop expressions	allow
set_allow_statement_expression	allows/disallows statement expressions	allow
set_allow_anonymous_fn (not available under [no_function])	allows/disallows [anonymous functions]	allow
set_allow_looping	allows/disallows looping (i.e. [while], [loop], [do] and [for] statements)	allow
set_allow_shadowing	allows/disallows [shadowing] of [variables]	allow
set_strict_variables	enables/disables [Strict Variables mode][strict variables]	disabled
set_fast_operators	enables/disables [Fast Operators mode][fast operators]	enabled
disable_symbol	disables a certain [keyword] or [operator] (see [disable keywords and operators])

Beware that these options activate during compile-time only. If an [AST] is compiled on an [Engine] but then evaluated on a different [Engine] with different configuration, disallowed features contained inside the [AST] will still run as normal.

Runtime Behavior

Method	Description
set_fail_on_invalid_map_property (not available under [no_object])	sets whether to raise errors (instead of returning [()]) when invalid properties are accessed on [object maps]
set_default_tag	sets the default value of the custom state (which can be obtained via [NativeCallContext::tag][NativeCallContext]) for each evaluation run

Safety Limits

Method	Not available under	Description
set_max_expr_depths	[unchecked]	sets the maximum nesting levels of an expression/statement (see [maximum statement depth])
set_max_call_levels	[unchecked], [no_function]	sets the maximum number of function call levels (default 50) to avoid infinite recursion (see [maximum call stack depth])
set_max_operations	[unchecked]	sets the maximum number of operations that a script is allowed to consume (see [maximum number of operations])
set_max_variables	[unchecked]	sets the maximum number of [variables] that a script is allowed to define within a single [Scope] (see [maximum number of variables])
set_max_functions	[unchecked], [no_function]	sets the maximum number of [functions] that a script is allowed to define (see [maximum number of functions])
set_max_modules	[unchecked], [no_modules]	sets the maximum number of [modules] that a script is allowed to load (see [maximum number of modules])
set_max_string_size	[unchecked]	sets the maximum length (in UTF-8 bytes) for [strings] (see [maximum length of strings])
set_max_array_size	[unchecked], [no_index]	sets the maximum size for [arrays] (see [maximum size of arrays])
set_max_map_size	[unchecked], [no_object]	sets the maximum number of properties for [object maps] (see [maximum size of object maps])
set_max_strings_interned		sets the maximum number of [strings] to be interned (if zero, the [strings interner] is disabled)