[devkit] IJPL-209914 support 'required-if-available' attribute syntax

(cherry picked from commit e0930eb490d772a9e003b2b01acc07f6b4199ec3)

GitOrigin-RevId: e5c494bde8133730e4fee38e339a63cfd93e0208

plugins/devkit/devkit-core/resources/documentation/plugin-descriptor.yaml

@@ -623,6 +623,18 @@ elements:
                             **This option isn't implemented yet and currently behaves the same way as `optional`.**
                         defaultValue: |
                           `optional`
+                    - attribute:
+                        name: required-if-available
+                        description: |
+                          **Experimental attribute**
+                          
+                          Specifies a condition when the loading rule should be restricted to 'required' instead of the rule given by the 'loading' attribute.
+                          The value of the attribute may reference one of the special content modules that reflect the configuration of the IDE:
+                          - `intellij.platform.frontend` 
+                          - `intellij.platform.backend` 
+                          - `intellij.platform.frontend.split`                          
+                          
+                          [Internal doc](https://youtrack.jetbrains.com/articles/IJPL-A-1503).
         - element:
             name: extensions
             references:

plugins/devkit/devkit-core/resources/intellij.devkit.core.xml

@@ -44,7 +44,7 @@
 
     <dom.fileMetaData implementation="org.jetbrains.idea.devkit.dom.impl.PluginDescriptorDomFileDescription"
                       rootTagName="idea-plugin"
-                      stubVersion="22"/>
+                      stubVersion="23"/>
     <dom.extender domClass="org.jetbrains.idea.devkit.dom.Extensions"
                   extenderClass="org.jetbrains.idea.devkit.dom.impl.ExtensionsDomExtender"/>
     <dom.extender domClass="org.jetbrains.idea.devkit.dom.Action"

plugins/devkit/devkit-core/src/dom/ContentDescriptor.java

@@ -33,6 +33,10 @@ public interface ContentDescriptor extends DomElement {
     @NotNull
     @Stubbed
     GenericAttributeValue<ModuleLoadingRule> getLoading();
+
+    @NotNull
+    @Stubbed
+    GenericAttributeValue<String> getRequiredIfAvailable();
     
     enum ModuleLoadingRule implements NamedEnum {
       REQUIRED("required"), EMBEDDED("embedded"), OPTIONAL("optional"), ON_DEMAND("on-demand");

plugins/devkit/devkit-java-tests/testData/pluginXmlDomStubs/pluginXmlStubs.xml

@@ -12,6 +12,10 @@
 
   <content>
     <module name="module.name"/>
+    <module name="optional.module" loading="optional"/>
+    <module name="required.module" loading="required"/>
+    <module name="ondemand.module" loading="on-demand"/>
+    <module name="required.in.frontend" required-if-available="intellij.platform.frontend"/>
   </content>
 
   <dependencies>

plugins/devkit/devkit-java-tests/testSrc/org/jetbrains/idea/devkit/codeInsight/PluginXmlDomStubsTest.java

@@ -46,6 +46,18 @@ public class PluginXmlDomStubsTest extends DomStubTest {
                         Element:content
                           Element:module
                             Attribute:name:module.name
+                          Element:module
+                            Attribute:name:optional.module
+                            Attribute:loading:optional
+                          Element:module
+                            Attribute:name:required.module
+                            Attribute:loading:required
+                          Element:module
+                            Attribute:name:ondemand.module
+                            Attribute:loading:on-demand
+                          Element:module
+                            Attribute:name:required.in.frontend
+                            Attribute:required-if-available:intellij.platform.frontend
                         Element:dependencies
                           Element:module
                             Attribute:name:dependencies.module