From 0311dedb3bf5cd63aaa144f592933f2fd6e19541 Mon Sep 17 00:00:00 2001
From: Michael Smithhisler <michael.smithhisler@hashicorp.com>
Date: Thu, 16 Oct 2025 14:50:53 -0400
Subject: [PATCH 1/2] Add default for MaxExpressions

Evaluating large numbers of expressions causes memory consumption to
balloon significantly. While this can be set by consumers of the
library, it is helpful to set a sane default that can be overridden if a
user chooses. This reduces the likelihood of accidental OOM failures.
---
 CHANGELOG.md  |  3 ++-
 bexpr.go      |  3 +++
 bexpr_test.go | 11 ++++++++---
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bfc7788..7c513ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,7 +3,8 @@
 ### Improvements
 
 ### Changes
+- Adds a default for max expressions to be evaluated.
 
 ### Fixed
 
-### Security
\ No newline at end of file
+### Security
diff --git a/bexpr.go b/bexpr.go
index 4b5a35c..5fff012 100644
--- a/bexpr.go
+++ b/bexpr.go
@@ -39,6 +39,9 @@ func CreateEvaluator(expression string, opts ...Option) (*Evaluator, error) {
 	var parserOpts []grammar.Option
 	if parsedOpts.withMaxExpressions != 0 {
 		parserOpts = append(parserOpts, grammar.MaxExpressions(parsedOpts.withMaxExpressions))
+	} else {
+		// Use sane default as large expressions consume significant memory
+		parserOpts = append(parserOpts, grammar.MaxExpressions(2000000))
 	}
 
 	ast, err := grammar.Parse("", []byte(expression), parserOpts...)
diff --git a/bexpr_test.go b/bexpr_test.go
index 3e0898f..2f11b94 100644
--- a/bexpr_test.go
+++ b/bexpr_test.go
@@ -21,18 +21,23 @@ func TestCreateEvaluator(t *testing.T) {
 		"basic": {
 			expression: "foo == 3",
 		},
+		"default max expressions": {
+			expression: "((((((((foo == 1))))))))",
+			// typo in pigeon code-gen
+			err: "max number of expresssions parsed",
+		},
 	}
 
 	for name, tcase := range tests {
-		name := name
-		tcase := tcase
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
-
 			expr, err := CreateEvaluator(tcase.expression)
 			if tcase.err == "" {
 				require.NoError(t, err)
 				require.NotNil(t, expr)
+			} else {
+				require.Error(t, err)
+				require.Contains(t, err.Error(), tcase.err)
 			}
 		})
 	}

From 1550e85d0c770ca4f85197066cf1b64b0d08c4d1 Mon Sep 17 00:00:00 2001
From: Michael Smithhisler <michael.smithhisler@hashicorp.com>
Date: Thu, 16 Oct 2025 16:24:21 -0400
Subject: [PATCH 2/2] update changelog and godoc

---
 CHANGELOG.md | 2 +-
 bexpr.go     | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7c513ac..895a749 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,7 +3,7 @@
 ### Improvements
 
 ### Changes
-- Adds a default for max expressions to be evaluated.
+- Adds a default of 2 million for max evaluated expressions.
 
 ### Fixed
 
diff --git a/bexpr.go b/bexpr.go
index 5fff012..de7c5e8 100644
--- a/bexpr.go
+++ b/bexpr.go
@@ -32,6 +32,7 @@ type Evaluator struct {
 
 // CreateEvaluator is used to create and configure a new Evaluator, the expression
 // will be used by the evaluator when evaluating against any supplied datum.
+// By default the evaluator will error after 2 million expressions.
 // The following Option types are supported:
 // WithHookFn, WithMaxExpressions, WithTagName, WithUnknownValue.
 func CreateEvaluator(expression string, opts ...Option) (*Evaluator, error) {