Editor: Return previewLink from post link only if available (#12800)

* Editor: Return previewLink from post link only if available

* Editor: Add CHANGELOG entry for publicly_queryable autosave fix

* Editor: Resolve previewLink lint errors

* Editor: Document autosave error handling

packages/editor/CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Bug Fixes
 
 - `getEditedPostAttribute` now correctly returns the merged result of edits as a partial change when given `'meta'` as the `attributeName`.
+- Fixes an error and unrecoverable state which occurs on autosave completion for a `'publicly_queryable' => false` post type.
 
 ## 9.0.4 (2018-11-30)
 

packages/editor/src/store/reducer.js

@@ -1300,17 +1300,23 @@ export function autosave( state = null, action ) {
 }
 
 /**
- * Reducer returning the poost preview link
+ * Reducer returning the post preview link.
  *
- * @param  {string?} state  The preview link
- * @param  {Object} action Dispatched action.
+ * @param {string?} state  The preview link
+ * @param {Object}  action Dispatched action.
  *
  * @return {string?} Updated state.
  */
 export function previewLink( state = null, action ) {
 	switch ( action.type ) {
 		case 'REQUEST_POST_UPDATE_SUCCESS':
-			return action.post.preview_link || addQueryArgs( action.post.link, { preview: true } );
+			if ( action.post.preview_link ) {
+				return action.post.preview_link;
+			} else if ( action.post.link ) {
+				return addQueryArgs( action.post.link, { preview: true } );
+			}
+
+			return state;
 
 		case 'REQUEST_POST_UPDATE_START':
 			// Invalidate known preview link when autosave starts.

packages/editor/src/store/test/reducer.js

@@ -37,6 +37,7 @@ import {
 	blockListSettings,
 	autosave,
 	postSavingLock,
+	previewLink,
 } from '../reducer';
 import { INITIAL_EDITS_DEFAULTS } from '../defaults';
 
@@ -2544,4 +2545,69 @@ describe( 'state', () => {
 			expect( state ).toEqual( {} );
 		} );
 	} );
+
+	describe( 'previewLink', () => {
+		it( 'returns null by default', () => {
+			const state = previewLink( undefined, {} );
+
+			expect( state ).toBe( null );
+		} );
+
+		it( 'returns preview link from save success', () => {
+			const state = previewLink( null, {
+				type: 'REQUEST_POST_UPDATE_SUCCESS',
+				post: {
+					preview_link: 'https://example.com/?p=2611&preview=true',
+				},
+			} );
+
+			expect( state ).toBe( 'https://example.com/?p=2611&preview=true' );
+		} );
+
+		it( 'returns post link with query arg from save success if no preview link', () => {
+			const state = previewLink( null, {
+				type: 'REQUEST_POST_UPDATE_SUCCESS',
+				post: {
+					link: 'https://example.com/sample-post/',
+				},
+			} );
+
+			expect( state ).toBe( 'https://example.com/sample-post/?preview=true' );
+		} );
+
+		it( 'returns same state if save success without preview link or post link', () => {
+			// Bug: This can occur for post types which are defined as
+			// `publicly_queryable => false` (non-viewable).
+			//
+			// See: https://github.com/WordPress/gutenberg/issues/12677
+			const state = previewLink( null, {
+				type: 'REQUEST_POST_UPDATE_SUCCESS',
+				post: {
+					preview_link: '',
+				},
+			} );
+
+			expect( state ).toBe( null );
+		} );
+
+		it( 'returns resets on preview start', () => {
+			const state = previewLink( 'https://example.com/sample-post/', {
+				type: 'REQUEST_POST_UPDATE_START',
+				options: {
+					isPreview: true,
+				},
+			} );
+
+			expect( state ).toBe( null );
+		} );
+
+		it( 'returns state on non-preview save start', () => {
+			const state = previewLink( 'https://example.com/sample-post/', {
+				type: 'REQUEST_POST_UPDATE_START',
+				options: {},
+			} );
+
+			expect( state ).toBe( 'https://example.com/sample-post/' );
+		} );
+	} );
 } );