Method optimizeRule

policy/composer.go:183–236

(ctx *cel.OptimizerContext, r *CompiledRule)

}

func (opt *ruleComposerImpl) optimizeRule(ctx *cel.OptimizerContext, r *CompiledRule) ast.Expr {
	// Visitor to rewrite variables-prefixed identifiers with index names.
	opt.enterScope()
	defer opt.exitScope()
	vars := r.Variables()
	for _, v := range vars {
		opt.registerVariable(ctx, v)
	}

	matches := r.Matches()
	matchCount := len(matches)
	var output compositionStep = nil
	// If the rule has an optional output, the last result in the ternary should return
	// `optional.none`. This output is implicit and created here to reflect the desired
	// last possible output of this type of rule.
	if r.HasOptionalOutput() {
		output = newOptionalCompositionStep(ctx, ctx.NewLiteral(types.True), ctx.NewCall("optional.none"))
	}
	// Build the rule subgraph.
	for i := matchCount - 1; i >= 0; i-- {
		m := matches[i]
		cond := ctx.CopyASTAndMetadata(m.Condition().NativeRep())

		// If the output is non-nil, then it is considered a non-optional output since
		// it is explictly stated. If the rule itself is optional, then the base case value
		// of output being optional.none() will convert the non-optional value to an optional
		// one.
		if m.Output() != nil {
			out := ctx.CopyASTAndMetadata(m.Output().Expr().NativeRep())
			step := newNonOptionalCompositionStep(ctx, cond, out)
			output = step.combine(output)
			continue
		}

		// If the match has a nested rule, then compute the rule and whether it has
		// an optional return value.
		child := m.NestedRule()
		nestedRule := opt.optimizeRule(ctx, child)
		nestedHasOptional := child.HasOptionalOutput()
		if nestedHasOptional {
			step := newOptionalCompositionStep(ctx, cond, nestedRule)
			output = step.combine(output)
			continue
		}
		step := newNonOptionalCompositionStep(ctx, cond, nestedRule)
		output = step.combine(output)
	}

	matchExpr := output.expr()
	identVisitor := opt.rewriteVariableName(ctx)
	ast.PostOrderVisit(matchExpr, identVisitor)

	return matchExpr
}

func (opt *ruleComposerImpl) rewriteVariableName(ctx *cel.OptimizerContext) ast.Visitor {
	return ast.NewExprVisitor(func(expr ast.Expr) {