fix(tabs): redisplay close button when more than one tab is closable (#11492)

**Related Issue:** #10183

## Summary
Redisplays x when > 1 closable tab is added programmatically.

Author: josercarcamo

packages/calcite-components/src/components/tab-nav/tab-nav.tsx

@@ -12,7 +12,6 @@ import {
   focusElementInGroup,
   FocusElementInGroupDestination,
   getElementDir,
-  slotChangeGetAssignedElements,
 } from "../../utils/dom";
 import { createObserver } from "../../utils/observers";
 import { Scale } from "../interfaces";
@@ -72,6 +71,8 @@ export class TabNav extends LitElement {
     return filterDirectChildren<TabTitle["el"]>(this.el, "calcite-tab-title");
   }
 
+  private makeFirstVisibleTabClosable = false;
+
   // #endregion
 
   // #region State Properties
@@ -367,14 +368,21 @@ export class TabNav extends LitElement {
     (event.currentTarget as HTMLDivElement).scrollBy(scrollByX, 0);
   }
 
-  private onSlotChange(event: Event): void {
+  private onSlotChange(): void {
     this.intersectionObserver?.disconnect();
 
-    const slottedElements = slotChangeGetAssignedElements(event, "calcite-tab-title");
-    slottedElements.forEach((child) => {
+    const tabTitles = this.tabTitles;
+    tabTitles.forEach((child) => {
       this.intersectionObserver?.observe(child);
     });
-    this.calciteInternalTabNavSlotChange.emit(slottedElements);
+    const visibleTabTitlesIndices = this.getVisibleTabTitlesIndices(tabTitles);
+    const totalVisibleTabTitles = visibleTabTitlesIndices.length;
+    if (totalVisibleTabTitles > 1 && this.makeFirstVisibleTabClosable) {
+      tabTitles[visibleTabTitlesIndices[0]].closable = true;
+      this.makeFirstVisibleTabClosable = false;
+    }
+
+    this.calciteInternalTabNavSlotChange.emit(tabTitles);
   }
 
   private storeTabTitleWrapperRef(el: HTMLDivElement) {
@@ -517,18 +525,23 @@ export class TabNav extends LitElement {
     });
   }
 
-  private handleTabTitleClose(closedTabTitleEl: TabTitle["el"]): void {
-    const { tabTitles } = this;
-    const selectionModified = closedTabTitleEl.selected;
-
-    const visibleTabTitlesIndices = tabTitles.reduce(
+  private getVisibleTabTitlesIndices(tabTitles: TabTitle["el"][]): number[] {
+    return tabTitles.reduce(
       (tabTitleIndices: number[], tabTitle, index) =>
         !tabTitle.closed ? [...tabTitleIndices, index] : tabTitleIndices,
       [],
     );
+  }
+
+  private handleTabTitleClose(closedTabTitleEl: TabTitle["el"]): void {
+    const { tabTitles } = this;
+    const selectionModified = closedTabTitleEl.selected;
+
+    const visibleTabTitlesIndices = this.getVisibleTabTitlesIndices(tabTitles);
     const totalVisibleTabTitles = visibleTabTitlesIndices.length;
 
     if (totalVisibleTabTitles === 1 && tabTitles[visibleTabTitlesIndices[0]].closable) {
+      this.makeFirstVisibleTabClosable = true;
       tabTitles[visibleTabTitlesIndices[0]].closable = false;
       this.selectedTabId = visibleTabTitlesIndices[0];
 

packages/calcite-components/src/components/tabs/tabs.e2e.ts

@@ -405,5 +405,45 @@ describe("calcite-tabs", () => {
 
       expect(selectedTitleOnEmit).toBe("Tab 2 Title");
     });
+
+    describe("hiding/displaying X", () => {
+      it("should hide x when tabs 2 to 4 closed and display x closable tab added", async () => {
+        for (let i = 2; i <= 4; ++i) {
+          await page.click(`#tab-title-${i} >>> .${TabTitleCSS.closeButton}`);
+        }
+        let tab1 = await page.find(`#tab-title-1`);
+        expect(await tab1.getProperty("closable")).toBe(false);
+        expect(await page.find(`#tab-title-1 >>> .${TabTitleCSS.closeButton}`)).toBeNull();
+
+        await page.evaluate(() => {
+          document
+            .getElementById("tab-title-4")
+            .insertAdjacentHTML("afterend", `<calcite-tab-title id="tab-title-5" closable>Test</calcite-tab-title>`);
+        });
+        await page.waitForChanges();
+        tab1 = await page.find(`#tab-title-1`);
+        expect(await tab1.getProperty("closable")).toBe(true);
+        expect(await page.find(`#tab-title-1 >>> .${TabTitleCSS.closeButton}`)).toBeDefined();
+      });
+
+      it("should hide x when tabs 1 to 3 closed and display x when closable tab added", async () => {
+        for (let i = 1; i <= 3; ++i) {
+          await page.click(`#tab-title-${i} >>> .${TabTitleCSS.closeButton}`);
+        }
+        let tab4 = await page.find(`#tab-title-4`);
+        expect(await tab4.getProperty("closable")).toBe(false);
+        expect(await page.find(`#tab-title-4 >>> .${TabTitleCSS.closeButton}`)).toBeNull();
+
+        await page.evaluate(() => {
+          document
+            .getElementById("tab-title-4")
+            .insertAdjacentHTML("afterend", `<calcite-tab-title id="tab-title-5" closable>Test</calcite-tab-title>`);
+        });
+        await page.waitForChanges();
+        tab4 = await page.find(`#tab-title-4`);
+        expect(await tab4.getProperty("closable")).toBe(true);
+        expect(await page.find(`#tab-title-4 >>> .${TabTitleCSS.closeButton}`)).toBeDefined();
+      });
+    });
   });
 });