Support hiding base editor (#705)

* Add ability to set showBase from CLI option

* Use DiffPanel for diff widgets

* Support merge view with 3 panels (theirs | final | ours) in addition to the current 4 panels views
Fixes #682

* Add integration tests

* Fix diff views

* Lint the code

* Fix final padding for merged editor in 3-panels view

* Fix scroll synchronization for 3-panels view

* Update Playwright Snapshots

* Update Playwright Snapshots

* Add delay to improve test robustness on Windows

* Change expectation

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

nbdime/args.py

@@ -465,6 +465,12 @@ def add_merge_args(parser):
         default=True,
         help="disallow deletion of transient data such as outputs and "
              "execution counts in order to resolve conflicts.")
+    parser.add_argument(
+        '--no-base',
+        dest='show_base',
+        action="store_false",
+        default=True,
+        help="Don't display the base version.")
 
 
 filename_help = {
@@ -532,6 +538,7 @@ def args_for_server(arguments):
                 workdirectory='cwd',
                 base_url='base_url',
                 hide_unchanged='hide_unchanged',
+                show_base='show_base',
                 )
     ret = {kmap[k]: v for k, v in vars(arguments).items() if k in kmap}
     if 'persist' in arguments:

nbdime/config.py

@@ -256,6 +256,11 @@ class Merge(_Diffing):
              "execution counts in order to resolve conflicts.",
     ).tag(config=True)
 
+    show_base = Bool(
+        True,
+        help="Whether to show the base version (4-panels) or not (3-panels).",
+    ).tag(config=True)
+
 
 class GitDiff(Diff):
     use_filter = Bool(

nbdime/webapp/nbdimeserver.py

@@ -189,6 +189,7 @@ def get(self):
         args['base'] = self.get_argument('base', '')
         args['local'] = self.get_argument('local', '')
         args['remote'] = self.get_argument('remote', '')
+        args['showBase'] = self.params.get('show_base', True)
         self.write(self.render_template('merge.html',
                     config_data=args,
                    ))
@@ -201,10 +202,12 @@ def get(self):
             args['base'] = self.params['mergetool_args']['base']
             args['local'] = self.params['mergetool_args']['local']
             args['remote'] = self.params['mergetool_args']['remote']
+            args['showBase'] = self.params.get('show_base', True)
         else:
             args['base'] = self.get_argument('base', '')
             args['local'] = self.get_argument('local', '')
             args['remote'] = self.get_argument('remote', '')
+            args['showBase'] = self.params.get('show_base', True)
         self.write(self.render_template('mergetool.html',
                     config_data=args,
                    ))

packages/nbdime/src/common/basepanel.ts

@@ -0,0 +1,36 @@
+// Copyright (c) Jupyter Development Team.
+// Distributed under the terms of the Modified BSD License.
+
+import { Panel } from '@lumino/widgets';
+import type { IDiffWidgetOptions, IMergeWidgetOptions } from './interfaces';
+import type { CodeEditor } from '@jupyterlab/codeeditor';
+
+/**
+ * Common panel for diff views
+ */
+export class DiffPanel<T> extends Panel {
+  constructor({ model, editorFactory }: IDiffWidgetOptions<T>) {
+    super();
+    this._editorFactory = editorFactory;
+    this._model = model;
+  }
+
+  protected _editorFactory: CodeEditor.Factory | undefined;
+  protected _model: T;
+}
+
+/**
+ * Common panel for merge views
+ */
+export class MergePanel<T> extends DiffPanel<T> {
+  constructor({
+    model,
+    editorFactory,
+    ...viewOptions
+  }: IDiffWidgetOptions<T> & IMergeWidgetOptions) {
+    super({ model, editorFactory });
+    this._viewOptions = viewOptions;
+  }
+
+  protected _viewOptions: IMergeWidgetOptions;
+}

packages/nbdime/src/common/interfaces.ts

@@ -1,18 +1,33 @@
 import type { CodeEditor } from '@jupyterlab/codeeditor';
 import type { IRenderMimeRegistry } from '@jupyterlab/rendermime';
 
+/**
+ * Common merge view options
+ */
+export interface IMergeWidgetOptions {
+  /**
+   * Whether to show the base version (4-panels) or not (3-panels).
+   */
+  showBase?: boolean;
+}
+
 /**
  * Main widget constructor options
  */
 // TODO `T` should be scoped down but more API rework will be needed on the model to achieve that
 // there is definitely room to rationalize the code with more abstract or mixin classes.
 export interface IDiffWidgetOptions<T> {
+  model: T;
+  editorFactory?: CodeEditor.Factory;
+}
+
+export interface IMimeDiffWidgetOptions<T> {
   model: T;
   rendermime: IRenderMimeRegistry;
   editorFactory?: CodeEditor.Factory;
 }
 
-export interface ICellDiffWidgetOptions<T> extends IDiffWidgetOptions<T> {
+export interface ICellDiffWidgetOptions<T> extends IMimeDiffWidgetOptions<T> {
   // TODO this seems redundant as mimetype is part of the model
   mimetype: string;
 }