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Empty branch in alternation

Reports empty branches in a RegExp alternation. An empty branch will only match the empty string, and in most cases that is not what is desired. This inspection will not report a single empty branch at the start or the end of an alternation.

Example:

(alpha||bravo)

After the quick-fix is applied:

(alpha|bravo)

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

RegExpEmptyAlternationBranch
Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | RegExp

New in 2017.2

Inspection ID: RegExpEmptyAlternationBranch

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection RegExpEmptyAlternationBranch

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

Last modified: 18 September 2025