Add a New Copy Button That Works in Modals

This copy button manages a local instance of the Clipboard plugin
specific to it, which means it is created/destroyed on the
creation/destruction of the component. This allows it to work well in
gitlab-ui modals, as the event listeners are bound on creation of the
button.

It also allows for bindings to the `container` option of the Clipboard
plugin, which allows it to work within the focus trap set by bootstrap's
modals.

app/assets/javascripts/vue_shared/components/modal_copy_button.vue

+<script>
+import $ from 'jquery';
+import { GlButton, GlTooltipDirective } from '@gitlab/ui';
+import { __ } from '~/locale';
+import Icon from '~/vue_shared/components/icon.vue';
+import Clipboard from 'clipboard';
+
+export default {
+  components: {
+    GlButton,
+    Icon,
+  },
+
+  directives: {
+    GlTooltip: GlTooltipDirective,
+  },
+
+  props: {
+    text: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    container: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    modalId: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    target: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    title: {
+      type: String,
+      required: true,
+    },
+    tooltipPlacement: {
+      type: String,
+      required: false,
+      default: 'top',
+    },
+    tooltipContainer: {
+      type: String,
+      required: false,
+      default: null,
+    },
+  },
+
+  copySuccessText: __('Copied'),
+
+  computed: {
+    modalDomId() {
+      return this.modalId ? `#${this.modalId}` : '';
+    },
+  },
+
+  mounted() {
+    this.$nextTick(() => {
+      this.clipboard = new Clipboard(this.$el, {
+        container:
+          document.querySelector(`${this.modalDomId} div.modal-content`) ||
+          document.getElementById(this.container) ||
+          document.body,
+      });
+      this.clipboard
+        .on('success', e => {
+          this.updateTooltip(e.trigger);
+          this.$emit('success', e);
+          // Clear the selection and blur the trigger so it loses its border
+          e.clearSelection();
+          $(e.trigger).blur();
+        })
+        .on('error', e => this.$emit('error', e));
+    });
+  },
+
+  destroyed() {
+    if (this.clipboard) {
+      this.clipboard.destroy();
+    }
+  },
+
+  methods: {
+    updateTooltip(target) {
+      const $target = $(target);
+      const originalTitle = $target.data('originalTitle');
+
+      if ($target.tooltip) {
+        /**
+         *  The original tooltip will continue staying there unless we remove it by hand.
+         *  $target.tooltip('hide') isn't working.
+         */
+        $('.tooltip').remove();
+        $target.attr('title', this.$options.copySuccessText);
+        $target.tooltip('_fixTitle');
+        $target.tooltip('show');
+        $target.attr('title', originalTitle);
+        $target.tooltip('_fixTitle');
+      }
+    },
+  },
+};
+</script>
+<template>
+  <gl-button
+    v-gl-tooltip="{ placement: tooltipPlacement, container: tooltipContainer }"
+    :data-clipboard-target="target"
+    :data-clipboard-text="text"
+    :title="title"
+  >
+    <slot>
+      <icon name="duplicate" />
+    </slot>
+  </gl-button>
+</template>

changelogs/unreleased/copy-button-in-modals.yml

+---
+title: Add a New Copy Button That Works in Modals
+merge_request: 28676
+author:
+type: added

doc/development/fe_guide/frontend_faq.md

@@ -25,3 +25,17 @@ document.body.dataset.page
 ```
 
 Find here the [source code setting the attribute](https://gitlab.com/gitlab-org/gitlab-ce/blob/cc5095edfce2b4d4083a4fb1cdc7c0a1898b9921/app/views/layouts/application.html.haml#L4).
+
+### `modal_copy_button` vs `clipboard_button`
+
+The `clipboard_button` uses the `copy_to_clipboard.js` behaviour, which is
+initialized on page load, so if there are vue-based clipboard buttons that
+don't exist at page load (such as ones in a `GlModal`), they do not have the
+click handlers associated with the clipboard package.
+
+`modal_copy_button` was added that manages an instance of the
+[`clipboard` plugin](https://www.npmjs.com/package/clipboard) specific to
+the instance of that component, which means that clipboard events are
+bound on mounting and destroyed when the button is, mitigating the above
+issue. It also has bindings to a particular container or modal ID
+available, to work with the focus trap created by our GlModal.

spec/frontend/vue_shared/components/modal_copy_button_spec.js

+import Vue from 'vue';
+import { shallowMount } from '@vue/test-utils';
+import modalCopyButton from '~/vue_shared/components/modal_copy_button.vue';
+
+describe('modal copy button', () => {
+  const Component = Vue.extend(modalCopyButton);
+  let wrapper;
+
+  afterEach(() => {
+    wrapper.destroy();
+  });
+
+  beforeEach(() => {
+    wrapper = shallowMount(Component, {
+      propsData: {
+        text: 'copy me',
+        title: 'Copy this value into Clipboard!',
+      },
+    });
+  });
+
+  describe('clipboard', () => {
+    it('should fire a `success` event on click', () => {
+      document.execCommand = jest.fn(() => true);
+      window.getSelection = jest.fn(() => ({
+        toString: jest.fn(() => 'test'),
+        removeAllRanges: jest.fn(),
+      }));
+      wrapper.trigger('click');
+      expect(wrapper.emitted().success).not.toBeEmpty();
+      expect(document.execCommand).toHaveBeenCalledWith('copy');
+    });
+    it("should propagate the clipboard error event if execCommand doesn't work", () => {
+      document.execCommand = jest.fn(() => false);
+      wrapper.trigger('click');
+      expect(wrapper.emitted().error).not.toBeEmpty();
+      expect(document.execCommand).toHaveBeenCalledWith('copy');
+    });
+  });
+});