From 847661acc2380309251ed1faf57711b7598c6270 Mon Sep 17 00:00:00 2001
From: danidomi <daniel.alexandre.domingues@gmail.com>
Date: Sat, 18 Oct 2025 14:40:24 +0100
Subject: [PATCH 1/2] add allowEmptyValue

---
 dsl/validation.go                     | 11 +++++++++++
 expr/attribute.go                     |  3 +++
 http/codegen/openapi/v3/parameters.go |  7 ++++++-
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/dsl/validation.go b/dsl/validation.go
index 4244a0b48c..cd9b80277e 100644
--- a/dsl/validation.go
+++ b/dsl/validation.go
@@ -381,6 +381,17 @@ func MinLength(val int) {
 	}
 }
 
+// AllowEmptyValue sets the AllowEmptyValue flag for a query or header parameter.
+// If not set, default behavior in paramFor is in != "path".
+func AllowEmptyValue(val bool) {
+	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
+		if a.Validation == nil {
+			a.Validation = &expr.ValidationExpr{}
+		}
+		a.Validation.AllowEmptyValue = val
+	}
+}
+
 // MaxLength adds a "maxItems" validation to the attribute.
 // See http://json-schema.org/latest/json-schema-validation.html#anchor42.
 //
diff --git a/expr/attribute.go b/expr/attribute.go
index 8f1ef9a181..73941500a3 100644
--- a/expr/attribute.go
+++ b/expr/attribute.go
@@ -98,6 +98,9 @@ type (
 		// described at
 		// http://json-schema.org/latest/json-schema-validation.html#anchor61.
 		Required []string
+		// AllowEmptyValue indicates whether the attribute allows empty
+		// values. This is primarily used for query string parameters.
+		AllowEmptyValue bool
 	}
 
 	// ValidationFormat is the type used to enumerate the possible string
diff --git a/http/codegen/openapi/v3/parameters.go b/http/codegen/openapi/v3/parameters.go
index b916a08d4d..4fedfbeea3 100644
--- a/http/codegen/openapi/v3/parameters.go
+++ b/http/codegen/openapi/v3/parameters.go
@@ -55,11 +55,16 @@ func paramsFromHeadersAndCookies(endpoint *expr.HTTPEndpointExpr, rand *expr.Exa
 
 // paramFor converts the given attribute into a OpenAPI spec parameter.
 func paramFor(att *expr.AttributeExpr, name, in string, required bool, rand *expr.ExampleGenerator) *Parameter {
+	allowEmpty := in != "path"
+	if att.Validation != nil {
+		allowEmpty = att.Validation.AllowEmptyValue
+	}
+
 	param := &Parameter{
 		Name:            name,
 		In:              in,
 		Description:     att.Description,
-		AllowEmptyValue: in != "path",
+		AllowEmptyValue: allowEmpty,
 		Required:        required,
 		Schema:          newSchemafier(rand).schemafy(att),
 		Extensions:      openapi.ExtensionsFromExpr(att.Meta),

From 4fc81724b76e584aeabb54c314f1345a5ded3ea7 Mon Sep 17 00:00:00 2001
From: danidomi <daniel.alexandre.domingues@gmail.com>
Date: Sun, 19 Oct 2025 18:54:37 +0100
Subject: [PATCH 2/2] add AllowEmptyValue bool

---
 dsl/validation.go                     | 2 +-
 expr/attribute.go                     | 2 +-
 http/codegen/openapi/v3/parameters.go | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/dsl/validation.go b/dsl/validation.go
index cd9b80277e..7aaa652ec1 100644
--- a/dsl/validation.go
+++ b/dsl/validation.go
@@ -388,7 +388,7 @@ func AllowEmptyValue(val bool) {
 		if a.Validation == nil {
 			a.Validation = &expr.ValidationExpr{}
 		}
-		a.Validation.AllowEmptyValue = val
+		a.Validation.AllowEmptyValue = &val
 	}
 }
 
diff --git a/expr/attribute.go b/expr/attribute.go
index 73941500a3..baf58c467b 100644
--- a/expr/attribute.go
+++ b/expr/attribute.go
@@ -100,7 +100,7 @@ type (
 		Required []string
 		// AllowEmptyValue indicates whether the attribute allows empty
 		// values. This is primarily used for query string parameters.
-		AllowEmptyValue bool
+		AllowEmptyValue *bool
 	}
 
 	// ValidationFormat is the type used to enumerate the possible string
diff --git a/http/codegen/openapi/v3/parameters.go b/http/codegen/openapi/v3/parameters.go
index 4fedfbeea3..3fde3b6be0 100644
--- a/http/codegen/openapi/v3/parameters.go
+++ b/http/codegen/openapi/v3/parameters.go
@@ -56,8 +56,8 @@ func paramsFromHeadersAndCookies(endpoint *expr.HTTPEndpointExpr, rand *expr.Exa
 // paramFor converts the given attribute into a OpenAPI spec parameter.
 func paramFor(att *expr.AttributeExpr, name, in string, required bool, rand *expr.ExampleGenerator) *Parameter {
 	allowEmpty := in != "path"
-	if att.Validation != nil {
-		allowEmpty = att.Validation.AllowEmptyValue
+	if att.Validation != nil && att.Validation.AllowEmptyValue != nil {
+		allowEmpty = *att.Validation.AllowEmptyValue
 	}
 
 	param := &Parameter{