Disable the Preview button when post type isn't viewable

editor/components/post-preview-button/index.js

@@ -1,8 +1,13 @@
+/**
+ * External dependencies
+ */
+import { get } from 'lodash';
+
 /**
  * WordPress dependencies
  */
 import { Component, compose } from '@wordpress/element';
-import { Button } from '@wordpress/components';
+import { Button, ifCondition } from '@wordpress/components';
 import { _x } from '@wordpress/i18n';
 import { withSelect, withDispatch } from '@wordpress/data';
 
@@ -117,16 +122,22 @@ export default compose( [
 			isEditedPostNew,
 			isEditedPostSaveable,
 		} = select( 'core/editor' );
+		const {
+			getPostType,
+		} = select( 'core' );
+		const postType = getPostType( getEditedPostAttribute( 'type' ) );
 		return {
 			postId: getCurrentPostId(),
 			link: getEditedPostPreviewLink(),
 			isDirty: isEditedPostDirty(),
 			isNew: isEditedPostNew(),
 			isSaveable: isEditedPostSaveable(),
+			isViewable: get( postType, 'viewable', false ),
 			modified: getEditedPostAttribute( 'modified' ),
 		};
 	} ),
 	withDispatch( ( dispatch )=>( {
 		autosave: dispatch( 'core/editor' ).autosave,
 	} ) ),
+	ifCondition( ( { isViewable } ) => isViewable ),
 ] )( PostPreviewButton );

phpunit/class-gutenberg-rest-api-test.php

@@ -96,4 +96,27 @@ function test_visibility_field_without_context() {
 
 		$this->assertFalse( isset( $result['visibility'] ) );
 	}
+
+	/**
+	 * Should return an extra viewable field on response when in edit context.
+	 */
+	function test_viewable_field() {
+		wp_set_current_user( $this->administrator );
+		$request = new WP_REST_Request( 'GET', '/wp/v2/types/post' );
+		$request->set_param( 'context', 'edit' );
+		$response = rest_do_request( $request );
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result['viewable'] ) );
+		$this->assertTrue( $result['viewable'] );
+	}
+
+	/**
+	 * Should not return viewable field without context set.
+	 */
+	function test_viewable_field_without_context() {
+		$request  = new WP_REST_Request( 'GET', '/wp/v2/types/post' );
+		$response = rest_do_request( $request );
+		$result   = $response->get_data();
+		$this->assertFalse( isset( $result['viewable'] ) );
+	}
 }

test/e2e/specs/hello.test.js

@@ -14,6 +14,8 @@ describe( 'hello', () => {
 		expect( page.url() ).toEqual( expect.stringContaining( 'post-new.php' ) );
 		const title = await page.$( '[placeholder="Add title"]' );
 		expect( title ).not.toBeNull();
+		const postPreviewButton = await page.$( '.editor-post-preview.button' );
+		expect( postPreviewButton ).not.toBeNull();
 	} );
 
 	it( 'Should have no history', async () => {