feat(tabs): add headerWidth prop (FE-4161)

src/components/tabs/__internal__/tabs-header/tabs-header.style.js

@@ -16,6 +16,7 @@ const StyledTabsHeaderWrapper = styled.div`
     css`
       overflow-y: auto;
       padding: 2px;
+      box-sizing: border-box;
 
       ${!isInSidebar &&
       css`

src/components/tabs/tabs.component.js

@@ -34,6 +34,7 @@ const Tabs = ({
   borders = "off",
   variant = "default",
   validationStatusOverride,
+  headerWidth,
   ...rest
 }) => {
   const tabRefs = useRef([]);
@@ -319,6 +320,7 @@ const Tabs = ({
       {...tagComponent("tabs", rest)}
       isInSidebar={isInSidebar}
       mt={position === "left" || isInSidebar ? "0px" : "15px"}
+      headerWidth={headerWidth}
       {...rest}
     >
       {renderTabHeaders()}
@@ -356,6 +358,18 @@ Tabs.propTypes = {
     "no right side",
     "no sides",
   ]),
+  /** sets width to the tab headers. Can be any valid CSS string.
+   * The headerWidth prop works only for `position="left"`
+   */
+  headerWidth: (props, propName, componentName) => {
+    if (props.position !== "left" && props[propName] !== undefined) {
+      return new Error(
+        `Invalid usage of prop ${propName} in ${componentName}. The ${propName} can be used only if position is set to left`
+      );
+    }
+
+    return null;
+  },
   /** Adds an alternate styling variant to the tab titles. */
   variant: PropTypes.oneOf(["default", "alternate"]),
   /** An object to support overriding validation statuses, when the Tabs have custom targets for example.

src/components/tabs/tabs.d.ts

@@ -26,6 +26,10 @@ export interface TabsProps extends MarginProps {
   borders?: "off" | "on" | "no left side" | "no right side" | "no sides";
   /** Adds an alternate styling variant to the tab titles. */
   variant?: "default" | "alternate";
+  /** sets width to the tab headers. Can be any valid CSS string.
+   * The headerWidth prop works only for `position="left"`
+   */
+  headerWidth?: string;
   /** An object to support overriding validation statuses, when the Tabs have custom targets for example.
    * The `id` property should match the `tabId`s for the rendered Tabs.
    */

src/components/tabs/tabs.spec.js

@@ -2,16 +2,19 @@
 import React, { useEffect, useContext } from "react";
 import { mount, shallow } from "enzyme";
 import { act } from "react-dom/test-utils";
+import { css } from "styled-components";
 import TabTitle from "./__internal__/tab-title/tab-title.component";
 import { Tabs, Tab } from "./tabs.component";
 import { TabContext } from "./tab/index";
 import { rootTagTest } from "../../utils/helpers/tags/tags-specs/tags-specs";
 import StyledTabs from "./tabs.style";
+import StyledTab from "./tab/tab.style";
 import {
   assertStyleMatch,
   simulate,
   testStyledSystemMargin,
 } from "../../__spec_helper__/test-utils";
+import { StyledTabsHeaderWrapper } from "./__internal__/tabs-header/tabs-header.style";
 import { SidebarContext } from "../drawer";
 
 function render(props) {
@@ -155,6 +158,66 @@ describe("Tabs", () => {
     { mt: "0px" }
   );
 
+  describe("when `headerWidth` is provided", () => {
+    describe.each(["35%", "100px", "5em"])(
+      "and value of %s is provided",
+      (headerWidth) => {
+        it("should render correct `width` in `TabsHeader` component, and `Tab` `width` should be `auto`", () => {
+          const wrapper = mount(
+            <Tabs position="left" headerWidth={headerWidth}>
+              <Tab title="Tab Title 1" tabId="uniqueid1">
+                TabContent
+              </Tab>
+            </Tabs>
+          );
+
+          assertStyleMatch(
+            {
+              width: headerWidth,
+            },
+            wrapper,
+            {
+              modifier: css`
+                ${StyledTabsHeaderWrapper}
+              `,
+            }
+          );
+
+          assertStyleMatch(
+            {
+              width: "auto",
+            },
+            wrapper,
+            {
+              modifier: css`
+                ${StyledTab}
+              `,
+            }
+          );
+        });
+      }
+    );
+  });
+
+  describe('when `headerWidth` is provided, and `position="top"`', () => {
+    it(" should render console error", () => {
+      jest.spyOn(global.console, "error").mockImplementation(() => {});
+
+      mount(
+        <Tabs position="top" headerWidth="500px">
+          <Tab title="Tab Title 1" tabId="uniqueid1">
+            TabContent
+          </Tab>
+        </Tabs>
+      );
+
+      // eslint-disable-next-line no-console
+      expect(console.error).toHaveBeenCalledWith(
+        "Warning: Failed prop type: Invalid usage of prop headerWidth in Tabs. The headerWidth can be used only if position is set to left\n    in Tabs"
+      );
+    });
+  });
+
   describe("when passing custom className as a prop", () => {
     it("adds it to the classList", () => {
       const wrapper = render({ className: "class" });

src/components/tabs/tabs.stories.js

@@ -1,5 +1,5 @@
 import React from "react";
-import { select, withKnobs } from "@storybook/addon-knobs";
+import { select, withKnobs, text } from "@storybook/addon-knobs";
 import { Tabs, Tab } from "./tabs.component";
 
 export default {
@@ -19,6 +19,7 @@ export default {
 export const Default = () => {
   return (
     <Tabs
+      headerWidth={text("headerWidth", "")}
       align={select("align", ["left", "right"], "left")}
       position={select("position", ["top", "left"], "top")}
       borders={select(

src/components/tabs/tabs.stories.mdx

@@ -1520,6 +1520,64 @@ By setting the `variant` prop to "alternate" it is possible to apply some additi
   </Story>
 </Preview>
 
+### With headerWidth
+The `headerWidth` prop works only if prop `position` is set to `left`.
+
+<Preview>
+  <Story name="with headerWidth">
+    {() => {
+      return (
+        <div style={{ padding: "4px" }}>
+          <Tabs headerWidth="400px" align="left" position="left">
+            <Tab
+              errorMessage="error"
+              warningMessage="warning"
+              infoMessage="info"
+              tabId="tab-1"
+              title="Very long title for Tab 1 without with prop it would be not well aligned with the second Tabs group"
+              key="tab-1"
+            >
+              Content for tab 1
+            </Tab>
+            <Tab
+              errorMessage="error"
+              warningMessage="warning"
+              infoMessage="info"
+              tabId="tab-2"
+              title="Tab 2"
+              key="tab-2"
+            >
+              Content for tab 2
+            </Tab>
+          </Tabs>
+          <Tabs headerWidth="400px" align="left" position="left">
+            <Tab
+              errorMessage="error"
+              warningMessage="warning"
+              infoMessage="info"
+              tabId="tab-1"
+              title="Tab 1"
+              key="tab-1"
+            >
+              Content for tab 1
+            </Tab>
+            <Tab
+              errorMessage="error"
+              warningMessage="warning"
+              infoMessage="info"
+              tabId="tab-2"
+              title="Tab 2"
+              key="tab-2"
+            >
+              Content for tab 2
+            </Tab>
+          </Tabs>
+        </div>
+      );
+    }}
+  </Story>
+</Preview>
+
 ### With custom spacing
 The `Tabs`component also allows you to pass custom margin spacing, whilst `Tab` components support custom padding spacings.
 The spacing modifiers support being passed either a number between 1 and 8 that is then multiplied by `8px` or any valid

src/components/tabs/tabs.style.js

@@ -2,13 +2,26 @@ import styled, { css } from "styled-components";
 import { margin } from "styled-system";
 import PropTypes from "prop-types";
 import BaseTheme from "../../style/themes/base";
+import { StyledTabsHeaderWrapper } from "./__internal__/tabs-header/tabs-header.style";
+import StyledTab from "./tab/tab.style";
 
 const StyledTabs = styled.div`
-  ${({ position, inSidebar, theme }) => css`
+  ${({ position, inSidebar, theme, headerWidth }) => css`
     color: ${theme.text.color};
 
     ${position === "left" &&
     css`
+      ${headerWidth &&
+      css`
+        ${StyledTabsHeaderWrapper} {
+          width: ${headerWidth};
+        }
+
+        ${StyledTab} {
+          width: auto;
+        }
+      `}
+
       ${!inSidebar &&
       css`
         display: flex;