Class BooleanExpressionEvaluator

Namespace: FlowOrchestrator.Core.Expressions

Assembly: FlowOrchestrator.Core.dll

Hand-rolled recursive-descent parser and evaluator for the limited boolean expression grammar supported by the When clause on RunAfterCondition.

public sealed class BooleanExpressionEvaluator

Inheritance: object

BooleanExpressionEvaluator

Inherited Members: object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

Grammar (informal):

expr        = orExpr
orExpr      = andExpr ("||" andExpr)*
andExpr     = notExpr ("&&" notExpr)*
notExpr     = "!" notExpr | comparison
comparison  = primary (("==" | "!=" | ">" | "<" | ">=" | "<=") primary)?
primary     = "(" expr ")" | literal | lhsExpression
literal     = number | string | "true" | "false" | "null"
lhsExpression = "@steps(...)" | "@triggerBody(...)" | "@triggerHeaders(...)"

The implementation is split across four internal files for readability: FlowOrchestrator.Core.Expressions.Internal.BooleanExpressionLexer (lex), FlowOrchestrator.Core.Expressions.Internal.BooleanExpressionParser (parse), BooleanExpressionAst.cs (AST + FlowOrchestrator.Core.Expressions.Internal.EvalContext), and FlowOrchestrator.Core.Expressions.Internal.BooleanExpressionComparer (type unification + binary comparison).

Type rules: number-vs-number compares as decimal; string-vs-string compares ordinally; bool-vs-bool compares directly; null is only equal/non-equal to null; any other type combination throws FlowExpressionException.

Short-circuit semantics: && does not evaluate the RHS when the LHS is false; || does not evaluate the RHS when the LHS is true.

Methods

EvaluateAsync(string, LhsResolverAsync)

Parses and evaluates expression, returning a trace that captures both the boolean result and a human-readable rewrite with each LHS replaced by its resolved value.

public ValueTask<WhenEvaluationTrace> EvaluateAsync(string expression, BooleanExpressionEvaluator.LhsResolverAsync resolver)

Parameters

expression string: The expression text from the manifest.
resolver BooleanExpressionEvaluator.LhsResolverAsync: A resolver invoked once per unique LHS token encountered during evaluation.

Returns

ValueTask<WhenEvaluationTrace>

Exceptions

FlowExpressionException: Thrown on parse errors or type-coercion failures.