Description
STS 4 includes Maven WTP support and basic support for WAR projects. By default in STS 4 WTP validation is enabled and WAR project building/refreshing activates various (default) WTP validators. However STS 4 is missing preferences for WTP validation configuration and also there is not direct way to suspend WTP validators. On bigger projects (e.g. having a lot of XML files) validation can take considerable amount of time and usually is not desired.
To reproduce create a new Java faceted project with facet "Dynamic Web Project" (or facet "Utility") - e.g. by creating Spring Starter maven WAR project. Add some XML resources (with errors). Initiated project build/update (e.g. Alt+F5 for m2e project) project. Notice "Validating 'project'" in progress view (that can take considerable time if there are a lot of XML or other resources that WTP validates by default). Also notice validation errors in the problems view of the type "XML problems" (not of the type "Language Server").
Workaround: import Eclipse preference (*.epf) with the setting
/instance/org.eclipse.wst.validation/suspend=true
in order to suspend all WTP validators.
STS 4 should disable WTP validation out of the box.