KB-2222 a!isNullOrEmpty returns false for lists containing only null or "" elements

Elly Meng — Thu, 29 Sep 2022 15:10:26 GMT

Current Revision posted to Appian Knowledge Base by Elly Meng on 9/29/2022 3:10:26 PM

Symptoms

a!isNullOrEmpty() returns false when the value being checked is a list containing only null or "" elements.

For example, a!isNullOrEmpty({null}) returns false.

Cause

This is expected behavior as a list with only null or "" elements is not an empty list. Additionally, a!isNullOrEmpty() does not iterate over lists to check for these elements in order to improve performance.

Please see the chart below for more examples of expected behavior regarding a!isNullOrEmpty() and lists:

Input	Output
`a!isNullOrEmpty({{}, ""})`	`false`
`a!isNullOrEmpty(cast(197, ""))`	`false`
`a!isNullOrEmpty({tostring(null), tointeger(null)})`	`false`
`a!isNullOrEmpty({null,null})`	`false`

Action

If a value is a list that may contain only null or "" elements, please consider using length() or a!forEach() to check if it is empty.

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: September 2022

Tags: application design

[DRAFT SP-7550 Unexpected behavior with a!isNullOrEmpty

Elly Meng — Fri, 23 Sep 2022 21:03:06 GMT

Revision 5 posted to Appian Knowledge Base by Elly Meng on 9/23/2022 9:03:06 PM

Symptoms

a!isNullOrEmpty() returns false when the value being checked is a list containing only null or "" elements.

For example, a!isNullOrEmpty({null}) returns false.

Cause

Please see the chart below for more examples of expected behavior regarding a!isNullOrEmpty() and lists:

Input	Output
`a!isNullOrEmpty({{}, ""})`	`false`
`a!isNullOrEmpty(cast(197, ""))`	`false`
`a!isNullOrEmpty({tostring(null), tointeger(null)})`	`false`
`a!isNullOrEmpty({null,null})`	`false`

Action

If a value is a list that may contain only null or "" elements, please consider using length() or a!forEach() to check if it is empty.

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: September 2022

Tags: application design

[DRAFT SP-7550 Unexpected behavior with a!isNullOrEmpty

Elly Meng — Fri, 23 Sep 2022 21:02:44 GMT

Revision 4 posted to Appian Knowledge Base by Elly Meng on 9/23/2022 9:02:44 PM

Symptoms

a!isNullOrEmpty() returns false when the value being checked is a list containing only null or "" elements. For example, a!isNullOrEmpty({null}) returns false.

Cause

Please see the chart below for more examples of expected behavior regarding a!isNullOrEmpty() and lists:

Input	Output
`a!isNullOrEmpty({{}, ""})`	`false`
`a!isNullOrEmpty(cast(197, ""))`	`false`
`a!isNullOrEmpty({tostring(null), tointeger(null)})`	`false`
`a!isNullOrEmpty({null,null})`	`false`

Action

If a value is a list that may contain only null or "" elements, please consider using length() or a!forEach() to check if it is empty.

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: September 2022

Tags: application design

DRAFT SP-7550 Unexpected behavior with a!isNullOrEmpty

Maggie Deppe-Walker — Mon, 22 Aug 2022 16:44:39 GMT

Revision 3 posted to Appian Knowledge Base by Maggie Deppe-Walker on 8/22/2022 4:44:39 PM

Symptoms

a!isNullOrEmpty({null}) returns false

Cause

This is expected product behavior. A set with the element null is not a null set.

Additionally, a!isNullOrEmpty() does not iterate over lists to check for null elements; the purpose of this is to keep the function's performance fast.

Please see the below chart for more examples of expected product behavior regarding a!isNullOrEmpty():

Input	Output
`a!isNullOrEmpty({{}, ""})`	`false`
`a!isNullOrEmpty(cast(197, ""))`	`false`
`a!isNullOrEmpty({tostring(null), tointeger(null)})`	`false`
`a!isNullOrEmpty({null,null})`	`false`

Action

If the value being checked is a list that may contain only null elements, please use the length() or a!forEach() functions

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: August 2022

Tags: application design