chore: Improve link mutiple issues UI

server-core/src/main/java/io/onedev/server/web/component/issue/choice/IssueMultiChoice.java

@@ -0,0 +1,41 @@
+package io.onedev.server.web.component.issue.choice;
+
+import static io.onedev.server.web.translation.Translation._T;
+
+import java.util.Collection;
+
+import org.apache.wicket.markup.head.IHeaderResponse;
+import org.apache.wicket.markup.head.JavaScriptHeaderItem;
+import org.apache.wicket.model.IModel;
+
+import io.onedev.server.model.Issue;
+import io.onedev.server.web.component.select2.Select2MultiChoice;
+
+public class IssueMultiChoice extends Select2MultiChoice<Issue> {
+
+	public IssueMultiChoice(String id, IModel<Collection<Issue>> model, IssueChoiceProvider choiceProvider) {
+		super(id, model, choiceProvider);
+	}
+
+	@Override
+	protected void onInitialize() {
+		super.onInitialize();
+		getSettings().setAllowClear(!isRequired());
+		if (isRequired())
+			getSettings().setPlaceholder(_T("Choose issues..."));
+		else
+			getSettings().setPlaceholder(_T("Not specified"));
+		getSettings().setFormatResult("onedev.server.issueChoiceFormatter.formatResult");
+		getSettings().setFormatSelection("onedev.server.issueChoiceFormatter.formatSelection");
+		getSettings().setEscapeMarkup("onedev.server.issueChoiceFormatter.escapeMarkup");
+		setConvertEmptyInputStringToNull(true);
+	}
+
+	@Override
+	public void renderHead(IHeaderResponse response) {
+		super.renderHead(response);
+		
+		response.render(JavaScriptHeaderItem.forReference(new IssueChoiceResourceReference()));
+	}
+	
+}

server-core/src/main/java/io/onedev/server/web/component/issue/choice/IssueSingleChoice.java

@@ -9,9 +9,9 @@ import org.apache.wicket.model.IModel;
 import io.onedev.server.model.Issue;
 import io.onedev.server.web.component.select2.Select2Choice;
 
-public class IssueChoice extends Select2Choice<Issue> {
+public class IssueSingleChoice extends Select2Choice<Issue> {
 
-	public IssueChoice(String id, IModel<Issue> model, IssueChoiceProvider choiceProvider) {
+	public IssueSingleChoice(String id, IModel<Issue> model, IssueChoiceProvider choiceProvider) {
 		super(id, model, choiceProvider);
 	}
 

server-core/src/main/java/io/onedev/server/web/component/issue/primary/IssuePrimaryPanel.java

@@ -416,11 +416,7 @@ public abstract class IssuePrimaryPanel extends Panel {
 					return editor;
 				}
 
-				private FormComponent<Issue> newLinkExistingPanel(String componentId) {
+				private IssueChoiceProvider getIssueChoiceProvider() {
-					return new SelectIssuePanel(componentId) {
-
-						@Override
-						protected IssueChoiceProvider getChoiceProvider() {
 					return new IssueChoiceProvider() {
 						@Override
 						protected Project getProject() {
@@ -438,10 +434,28 @@ public abstract class IssuePrimaryPanel extends Panel {
 						
 					};						
 				}
+
+				private FormComponent<?> newLinkExistingPanel(String componentId) {
+					LinkSpec spec = getLinkSpecManager().load(specId);
+					if (!opposite && spec.isMultiple() || opposite && spec.getOpposite().isMultiple()) {
+						return new SelectIssuesPanel(componentId) {
+
+							@Override
+							protected IssueChoiceProvider getChoiceProvider() {
+								return getIssueChoiceProvider();						
+							}
+						};
+					} else {
+						return new SelectIssuePanel(componentId) {
+							@Override
+							protected IssueChoiceProvider getChoiceProvider() {
+								return getIssueChoiceProvider();
+							}
 						};
 					}
+				}
 
-				private FormComponent<Issue> issuePopulator;
+				private FormComponent<?> issuePopulator;
 
 				@Override
 				protected Component newContent(String id) {
@@ -511,30 +525,50 @@ public abstract class IssuePrimaryPanel extends Panel {
 					form.add(new Label("title", MessageFormat.format(_T("Add {0}"), linkName)));
 
 					form.add(new AjaxButton("save") {
+						@SuppressWarnings("unchecked")
 						@Override
 						protected void onSubmit(AjaxRequestTarget target, Form<?> form) {
-							var linkIssue = issuePopulator.getConvertedInput();
+							var convertedInput = issuePopulator.getConvertedInput();
+							if (convertedInput instanceof Issue) {
+								var linkIssue = (Issue) convertedInput;
 								if (linkIssue.isNew()) {
 									getIssueManager().open(linkIssue);
 									notifyIssueChange(target, linkIssue);
-								var spec = getLinkSpecManager().load(specId);
+									addLink(target, linkIssue);
-								getIssueChangeManager().addLink(spec, getIssue(), linkIssue, opposite);
-								notifyIssueChange(target, getIssue());
 									close();
+								} else if (checkLink(target, linkIssue)) {
+									addLink(target, linkIssue);
+									close();
+								}
 							} else {
+								var linkIssues = (List<Issue>) convertedInput;
+								if (linkIssues.stream().noneMatch(it->!checkLink(target, it))) {
+									for (var linkIssue: linkIssues) 
+										addLink(target, linkIssue);
+									close();
+								}
+							}
+						}
+
+						private boolean checkLink(AjaxRequestTarget target, Issue linkIssue) {
 							LinkSpec spec = getLinkSpecManager().load(specId);
 							if (getIssue().getId().equals(linkIssue.getId())) {
-									form.error(_T("Can not link to self"));
+								form.error(_T("Can not link to self: " + linkIssue.getReference().toString(getProject())));
 								target.add(form);
+								return false;
 							} else if (getIssue().findLinkedIssues(spec, opposite).contains(linkIssue)) { 
-									form.error(_T("Issue already linked"));
+								form.error(_T("Issue already linked: " + linkIssue.getReference().toString(getProject())));
 								target.add(form);
+								return false;
 							} else {
+								return true;
+							}	
+						}
+
+						private void addLink(AjaxRequestTarget target, Issue linkIssue) {
+							LinkSpec spec = getLinkSpecManager().load(specId);
 							getIssueChangeManager().addLink(spec, getIssue(), linkIssue, opposite);
 							notifyIssueChange(target, getIssue());
-									close();
-								}	
-							}
 						}
 
 						@Override

server-core/src/main/java/io/onedev/server/web/component/issue/primary/SelectIssuePanel.java

@@ -8,14 +8,14 @@ import org.apache.wicket.model.Model;
 import io.onedev.server.OneDev;
 import io.onedev.server.entitymanager.IssueManager;
 import io.onedev.server.model.Issue;
-import io.onedev.server.web.component.issue.choice.IssueChoice;
 import io.onedev.server.web.component.issue.choice.IssueChoiceProvider;
+import io.onedev.server.web.component.issue.choice.IssueSingleChoice;
 
 abstract class SelectIssuePanel extends FormComponentPanel<Issue> {
 
     private Long issueId;
 
-    private IssueChoice choice;
+    private IssueSingleChoice choice;
 
     public SelectIssuePanel(String id) {
         super(id, Model.of((Issue)null));
@@ -26,7 +26,7 @@ abstract class SelectIssuePanel extends FormComponentPanel<Issue> {
         super.onInitialize();
 
         add(new FencedFeedbackPanel("feedback"));
-        choice = new IssueChoice("choice", new IModel<Issue>() {
+        choice = new IssueSingleChoice("choice", new IModel<Issue>() {
 
             @Override
             public void detach() {

server-core/src/main/java/io/onedev/server/web/component/issue/primary/SelectIssuesPanel.html

@@ -0,0 +1,4 @@
+<wicket:panel>
+    <div wicket:id="feedback"></div>
+    <input wicket:id="choice" type="hidden" class="form-control">
+</wicket:panel>

server-core/src/main/java/io/onedev/server/web/component/issue/primary/SelectIssuesPanel.java

@@ -0,0 +1,83 @@
+package io.onedev.server.web.component.issue.primary;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+import org.apache.wicket.feedback.FencedFeedbackPanel;
+import org.apache.wicket.markup.html.form.FormComponentPanel;
+import org.apache.wicket.model.IModel;
+
+import io.onedev.server.OneDev;
+import io.onedev.server.entitymanager.IssueManager;
+import io.onedev.server.model.Issue;
+import io.onedev.server.web.component.issue.choice.IssueChoiceProvider;
+import io.onedev.server.web.component.issue.choice.IssueMultiChoice;
+
+abstract class SelectIssuesPanel extends FormComponentPanel<Collection<Issue>> {
+
+    private Collection<Long> issueIds = new ArrayList<>();
+
+    private IssueMultiChoice choice;
+
+    public SelectIssuesPanel(String id) {
+        super(id, new IModel<Collection<Issue>>() {
+
+            private Collection<Issue> collection = new ArrayList<Issue>();
+
+            @Override
+            public void detach() {
+            }
+            @Override
+            public Collection<Issue> getObject() {
+                return collection;
+            }
+            @Override
+            public void setObject(Collection<Issue> object) {
+                collection = object;
+            }
+        });
+    }
+
+    @Override
+    protected void onInitialize() {
+        super.onInitialize();
+
+        add(new FencedFeedbackPanel("feedback"));
+        choice = new IssueMultiChoice("choice", new IModel<Collection<Issue>>() {
+
+            @Override
+            public void detach() {
+            }
+
+            @Override
+            public Collection<Issue> getObject() {
+                return issueIds.stream().map(it->getIssueManager().load(it)).collect(Collectors.toList());
+            }
+
+            @Override
+            public void setObject(Collection<Issue> object) {
+                issueIds = object.stream().map(it->it.getId()).collect(Collectors.toList());
+            }
+
+        }, getChoiceProvider());        
+
+        choice.setRequired(true);
+        add(choice);
+
+        setOutputMarkupId(true);
+    }
+
+    @Override
+    public void convertInput() {
+        super.convertInput();
+        setConvertedInput(choice.getConvertedInput());
+    }
+    
+    protected abstract IssueChoiceProvider getChoiceProvider();
+
+    private IssueManager getIssueManager() {
+        return OneDev.getInstance(IssueManager.class);
+    }
+
+}

server-core/src/main/java/io/onedev/server/web/editable/issue/choice/IssueChoiceEditor.java

@@ -13,7 +13,7 @@ import io.onedev.server.entitymanager.IssueManager;
 import io.onedev.server.model.Issue;
 import io.onedev.server.model.Project;
 import io.onedev.server.search.entity.issue.IssueQuery;
-import io.onedev.server.web.component.issue.choice.IssueChoice;
+import io.onedev.server.web.component.issue.choice.IssueSingleChoice;
 import io.onedev.server.web.component.issue.choice.IssueChoiceProvider;
 import io.onedev.server.web.editable.PropertyDescriptor;
 import io.onedev.server.web.editable.PropertyEditor;
@@ -22,7 +22,7 @@ import io.onedev.server.web.util.ProjectAware;
 
 public class IssueChoiceEditor extends PropertyEditor<Long> {
 
-	private IssueChoice input;
+	private IssueSingleChoice input;
 	
 	public IssueChoiceEditor(String id, PropertyDescriptor propertyDescriptor, 
 			IModel<Long> propertyModel) {
@@ -64,7 +64,7 @@ public class IssueChoiceEditor extends PropertyEditor<Long> {
 			}
 			
 		};
-    	input = new IssueChoice("input", Model.of(issue), choiceProvider) {
+    	input = new IssueSingleChoice("input", Model.of(issue), choiceProvider) {
 
     		@Override
 			protected void onInitialize() {