File length validation for task order upload

atst/forms/task_order.py

@@ -4,6 +4,7 @@ from wtforms.validators import Required, Optional
 from flask_wtf.file import FileAllowed
 
 from .forms import BaseForm
+from atst.forms.validators import FileLength
 from atst.utils.localization import translate
 
 
@@ -16,7 +17,8 @@ class TaskOrderForm(BaseForm):
     pdf = FileField(
         None,
         validators=[
-            FileAllowed(["pdf"], translate("forms.task_order.file_format_not_allowed"))
+            FileAllowed(["pdf"], translate("forms.task_order.file_format_not_allowed")),
+            FileLength(),
         ],
         render_kw={"accept": ".pdf,application/pdf"},
     )

atst/forms/validators.py

@@ -99,3 +99,17 @@ def RequiredIf(criteria_function, message=translate("forms.validators.is_require
             raise StopValidation()
 
     return _required_if
+
+
+def FileLength(max_length=50000000, message=None):
+    def _file_length(_form, field):
+        if field.data is None:
+            return True
+
+        content = field.data.read()
+        if len(content) > max_length:
+            raise ValidationError(message)
+        else:
+            field.data.seek(0)
+
+    return _file_length