fix PreferenceChangeEvent<T> type

examples/api-samples/src/browser/file-watching/sample-file-watching-contribution.ts

@@ -69,7 +69,7 @@ class SampleFileWatchingContribution implements FrontendApplicationContribution
         this.verbose = this.fileWatchingPreferences['sample.file-watching.verbose'];
         this.fileWatchingPreferences.onPreferenceChanged(e => {
             if (e.preferenceName === 'sample.file-watching.verbose') {
-                this.verbose = e.newValue!;
+                this.verbose = e.newValue;
             }
         });
     }

packages/core/src/browser/preferences/preference-proxy.ts

@@ -21,12 +21,61 @@ import { PreferenceService } from './preference-service';
 import { PreferenceSchema, OverridePreferenceName } from './preference-contribution';
 import { PreferenceScope } from './preference-scope';
 
-export interface PreferenceChangeEvent<T> {
-    readonly preferenceName: keyof T;
-    readonly newValue?: T[keyof T];
-    readonly oldValue?: T[keyof T];
+/**
+ * It is worth explaining the type for `PreferenceChangeEvent`:
+ *
+ * // Given T:
+ * type T = { a: string, b: number }
+ *
+ * // We construct a new type such as:
+ * type U = {
+ *     a: {
+ *         preferenceName: 'a'
+ *         newValue: string
+ *         oldValue?: string
+ *     }
+ *     b: {
+ *        preferenceName: 'b'
+ *        newValue: number
+ *        oldValue?: number
+ *     }
+ * }
+ *
+ * // Then we get the union of all values of U by selecting by `keyof T`:
+ * type V = U[keyof T]
+ *
+ * // Implementation:
+ * type PreferenceChangeEvent<T> = {
+ *     // Create a mapping where each key is a key from T,
+ *     // -? normalizes optional typings to avoid getting
+ *     // `undefined` as part of the final union:
+ *     [K in keyof T]-?: {
+ *         // In this object, K will take the value of each
+ *         // independent key from T:
+ *         preferenceName: K
+ *         newValue: T[K]
+ *         oldValue?: T[K]
+ *     // Finally we create the union by doing so:
+ *     }[keyof T]
+ * }
+ */
+
+/**
+ * Union of all possible key/value pairs for a type `T`
+ */
+export type PreferenceChangeEvent<T> = {
     affects(resourceUri?: string, overrideIdentifier?: string): boolean;
-}
+} & {
+    [K in keyof T]-?: {
+        readonly preferenceName: K;
+        readonly newValue: T[K];
+        /**
+         * Undefined if the preference is set for the first time.
+         */
+        // TODO: Use the default value instead of undefined?
+        readonly oldValue?: T[K];
+    }
+}[keyof T];
 
 export interface PreferenceEventEmitter<T> {
     readonly onPreferenceChanged: Event<PreferenceChangeEvent<T>>;

packages/git/src/browser/diff/git-diff-widget.tsx

@@ -16,7 +16,7 @@
 
 import { inject, injectable, postConstruct } from 'inversify';
 import {
-    BaseWidget, Widget, StatefulWidget, Panel, PanelLayout, Message, MessageLoop, PreferenceChangeEvent
+    BaseWidget, Widget, StatefulWidget, Panel, PanelLayout, Message, MessageLoop
 } from '@theia/core/lib/browser';
 import { EditorManager, DiffNavigatorProvider } from '@theia/editor/lib/browser';
 import { GitDiffTreeModel } from './git-diff-tree-model';
@@ -25,7 +25,7 @@ import { GitDiffHeaderWidget } from './git-diff-header-widget';
 import { ScmService } from '@theia/scm/lib/browser/scm-service';
 import { GitRepositoryProvider } from '../git-repository-provider';
 import { ScmTreeWidget } from '@theia/scm/lib/browser/scm-tree-widget';
-import { ScmPreferences, ScmConfiguration } from '@theia/scm/lib/browser/scm-preferences';
+import { ScmPreferences } from '@theia/scm/lib/browser/scm-preferences';
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
@@ -76,9 +76,9 @@ export class GitDiffWidget extends BaseWidget implements StatefulWidget {
         this.containerLayout.addWidget(this.resourceWidget);
 
         this.updateViewMode(this.scmPreferences.get('scm.defaultViewMode'));
-        this.toDispose.push(this.scmPreferences.onPreferenceChanged((e: PreferenceChangeEvent<ScmConfiguration>) => {
+        this.toDispose.push(this.scmPreferences.onPreferenceChanged(e => {
             if (e.preferenceName === 'scm.defaultViewMode') {
-                this.updateViewMode(e.newValue!);
+                this.updateViewMode(e.newValue);
             }
         }));
     }

packages/git/src/browser/history/git-commit-detail-widget.tsx

@@ -19,14 +19,14 @@
 import { Message } from '@phosphor/messaging';
 import { injectable, inject, postConstruct } from 'inversify';
 import {
-    BaseWidget, Widget, StatefulWidget, Panel, PanelLayout, MessageLoop, PreferenceChangeEvent
+    BaseWidget, Widget, StatefulWidget, Panel, PanelLayout, MessageLoop
 } from '@theia/core/lib/browser';
 import { GitCommitDetailWidgetOptions } from './git-commit-detail-widget-options';
 import { GitCommitDetailHeaderWidget } from './git-commit-detail-header-widget';
 import { ScmService } from '@theia/scm/lib/browser/scm-service';
 import { GitDiffTreeModel } from '../diff/git-diff-tree-model';
 import { ScmTreeWidget } from '@theia/scm/lib/browser/scm-tree-widget';
-import { ScmPreferences, ScmConfiguration } from '@theia/scm/lib/browser/scm-preferences';
+import { ScmPreferences } from '@theia/scm/lib/browser/scm-preferences';
 
 @injectable()
 export class GitCommitDetailWidget extends BaseWidget implements StatefulWidget {
@@ -76,9 +76,9 @@ export class GitCommitDetailWidget extends BaseWidget implements StatefulWidget
         this.containerLayout.addWidget(this.resourceWidget);
 
         this.updateViewMode(this.scmPreferences.get('scm.defaultViewMode'));
-        this.toDispose.push(this.scmPreferences.onPreferenceChanged((e: PreferenceChangeEvent<ScmConfiguration>) => {
+        this.toDispose.push(this.scmPreferences.onPreferenceChanged(e => {
             if (e.preferenceName === 'scm.defaultViewMode') {
-                this.updateViewMode(e.newValue!);
+                this.updateViewMode(e.newValue);
             }
         }));
 

packages/markers/src/browser/problem/problem-decorator.ts

@@ -25,8 +25,7 @@ import { TreeDecorator, TreeDecoration } from '@theia/core/lib/browser/tree/tree
 import { FileStatNode } from '@theia/filesystem/lib/browser';
 import { Marker } from '../../common/marker';
 import { ProblemManager } from './problem-manager';
-import { ProblemPreferences, ProblemConfiguration } from './problem-preferences';
-import { PreferenceChangeEvent } from '@theia/core/lib/browser';
+import { ProblemPreferences } from './problem-preferences';
 import { ProblemUtils } from './problem-utils';
 
 @injectable()
@@ -46,10 +45,9 @@ export class ProblemDecorator implements TreeDecorator {
 
     @postConstruct()
     protected init(): void {
-        this.problemPreferences.onPreferenceChanged((event: PreferenceChangeEvent<ProblemConfiguration>) => {
-            const { preferenceName } = event;
-            if (preferenceName === 'problems.decorations.enabled') {
-                this.fireDidChangeDecorations((tree: Tree) => this.collectDecorators(tree));
+        this.problemPreferences.onPreferenceChanged(event => {
+            if (event.preferenceName === 'problems.decorations.enabled') {
+                this.fireDidChangeDecorations(tree => this.collectDecorators(tree));
             }
         });
     }

packages/monaco/src/browser/textmate/monaco-textmate-service.ts

@@ -103,7 +103,7 @@ export class MonacoTextmateService implements FrontendApplicationContribution {
         this.tokenizerOption.lineLimit = this.preferences['editor.maxTokenizationLineLength'];
         this.preferences.onPreferenceChanged(e => {
             if (e.preferenceName === 'editor.maxTokenizationLineLength') {
-                this.tokenizerOption.lineLimit = this.preferences['editor.maxTokenizationLineLength'];
+                this.tokenizerOption.lineLimit = e.newValue;
             }
         });
 

packages/output/src/common/output-channel.ts

@@ -25,7 +25,6 @@ import { MonacoTextModelService, IReference } from '@theia/monaco/lib/browser/mo
 import { OutputUri } from './output-uri';
 import { OutputResource } from '../browser/output-resource';
 import { OutputPreferences } from './output-preferences';
-import { OutputConfigSchema } from './output-preferences';
 
 @injectable()
 export class OutputChannelManager implements Disposable, ResourceResolver {
@@ -221,9 +220,9 @@ export class OutputChannel implements Disposable {
         this._maxLineNumber = this.preferences['output.maxChannelHistory'];
         this.toDispose.push(resource);
         this.toDispose.push(Disposable.create(() => this.decorationIds.clear()));
-        this.toDispose.push(this.preferences.onPreferenceChanged(({ preferenceName, newValue }) => {
-            if (preferenceName === 'output.maxChannelHistory') {
-                const maxLineNumber = newValue ? newValue : OutputConfigSchema.properties['output.maxChannelHistory'].default;
+        this.toDispose.push(this.preferences.onPreferenceChanged(event => {
+            if (event.preferenceName === 'output.maxChannelHistory') {
+                const maxLineNumber = event.newValue;
                 if (this.maxLineNumber !== maxLineNumber) {
                     this.maxLineNumber = maxLineNumber;
                 }

packages/preview/src/browser/preview-widget.ts

@@ -83,7 +83,7 @@ export class PreviewWidget extends BaseWidget implements Navigatable {
         this.scrollBeyondLastLine = !!this.editorPreferences['editor.scrollBeyondLastLine'];
         this.toDispose.push(this.editorPreferences.onPreferenceChanged(e => {
             if (e.preferenceName === 'editor.scrollBeyondLastLine') {
-                this.scrollBeyondLastLine = !!e.newValue;
+                this.scrollBeyondLastLine = e.newValue;
                 this.forceUpdate();
             }
         }));

packages/scm/src/browser/scm-widget.tsx

@@ -20,14 +20,14 @@ import { Message } from '@phosphor/messaging';
 import { injectable, inject, postConstruct } from 'inversify';
 import { DisposableCollection } from '@theia/core/lib/common/disposable';
 import {
-    BaseWidget, Widget, StatefulWidget, Panel, PanelLayout, MessageLoop, PreferenceChangeEvent, CompositeTreeNode, SelectableTreeNode,
+    BaseWidget, Widget, StatefulWidget, Panel, PanelLayout, MessageLoop, CompositeTreeNode, SelectableTreeNode,
 } from '@theia/core/lib/browser';
 import { ScmCommitWidget } from './scm-commit-widget';
 import { ScmAmendWidget } from './scm-amend-widget';
 import { ScmNoRepositoryWidget } from './scm-no-repository-widget';
 import { ScmService } from './scm-service';
 import { ScmTreeWidget } from './scm-tree-widget';
-import { ScmPreferences, ScmConfiguration } from './scm-preferences';
+import { ScmPreferences } from './scm-preferences';
 
 @injectable()
 export class ScmWidget extends BaseWidget implements StatefulWidget {
@@ -78,9 +78,9 @@ export class ScmWidget extends BaseWidget implements StatefulWidget {
         this.refresh();
         this.toDispose.push(this.scmService.onDidChangeSelectedRepository(() => this.refresh()));
         this.updateViewMode(this.scmPreferences.get('scm.defaultViewMode'));
-        this.toDispose.push(this.scmPreferences.onPreferenceChanged((e: PreferenceChangeEvent<ScmConfiguration>) => {
+        this.toDispose.push(this.scmPreferences.onPreferenceChanged(e => {
             if (e.preferenceName === 'scm.defaultViewMode') {
-                this.updateViewMode(e.newValue!);
+                this.updateViewMode(e.newValue);
             }
         }));
 

packages/terminal/src/browser/terminal-preferences.ts

@@ -151,6 +151,7 @@ export const TerminalConfigSchema: PreferenceSchema = {
 export interface TerminalConfiguration {
     'terminal.enableCopy': boolean
     'terminal.enablePaste': boolean
+    // xterm compatible, see https://xtermjs.org/docs/api/terminal/interfaces/iterminaloptions/
     'terminal.integrated.fontFamily': string
     'terminal.integrated.fontSize': number
     'terminal.integrated.fontWeight': FontWeight
@@ -165,9 +166,9 @@ export interface TerminalConfiguration {
     'terminal.integrated.cursorBlinking': boolean,
     'terminal.integrated.cursorStyle': CursorStyleVSCode,
     'terminal.integrated.cursorWidth': number,
-    'terminal.integrated.shell.windows': string | undefined,
-    'terminal.integrated.shell.osx': string | undefined,
-    'terminal.integrated.shell.linux': string | undefined,
+    'terminal.integrated.shell.windows': string | null | undefined,
+    'terminal.integrated.shell.osx': string | null | undefined,
+    'terminal.integrated.shell.linux': string | null | undefined,
     'terminal.integrated.shellArgs.windows': string[],
     'terminal.integrated.shellArgs.osx': string[],
     'terminal.integrated.shellArgs.linux': string[],

packages/terminal/src/browser/terminal-widget-impl.ts

@@ -148,18 +148,16 @@ export class TerminalWidgetImpl extends TerminalWidget implements StatefulWidget
             const lastSeparator = change.preferenceName.lastIndexOf('.');
             if (lastSeparator > 0) {
                 let preferenceName = change.preferenceName.substr(lastSeparator + 1);
-                let preferenceValue = this.preferences[change.preferenceName];
+                let preferenceValue = change.newValue;
 
                 if (preferenceName === 'rendererType') {
-                    const newRendererType: string = this.preferences[change.preferenceName] as string;
+                    const newRendererType = preferenceValue as string;
                     if (newRendererType !== this.getTerminalRendererType(newRendererType)) {
-                        // given terminal renderer type is not supported or invalid
+                        // Given terminal renderer type is not supported or invalid
                         preferenceValue = DEFAULT_TERMINAL_RENDERER_TYPE;
                     }
-                }
-
-                // Convert the terminal preference into a valid `xterm` option.
-                if (preferenceName === 'cursorBlinking') {
+                } else if (preferenceName === 'cursorBlinking') {
+                    // Convert the terminal preference into a valid `xterm` option
                     preferenceName = 'cursorBlink';
                 } else if (preferenceName === 'cursorStyle') {
                     preferenceValue = this.getCursorStyle();
@@ -635,9 +633,9 @@ export class TerminalWidgetImpl extends TerminalWidget implements StatefulWidget
     protected get shellPreferences(): IShellTerminalPreferences {
         return {
             shell: {
-                Windows: this.preferences['terminal.integrated.shell.windows'],
-                Linux: this.preferences['terminal.integrated.shell.linux'],
-                OSX: this.preferences['terminal.integrated.shell.osx'],
+                Windows: this.preferences['terminal.integrated.shell.windows'] ?? undefined,
+                Linux: this.preferences['terminal.integrated.shell.linux'] ?? undefined,
+                OSX: this.preferences['terminal.integrated.shell.osx'] ?? undefined,
             },
             shellArgs: {
                 Windows: this.preferences['terminal.integrated.shellArgs.windows'],

packages/workspace/src/browser/workspace-service.ts

@@ -95,8 +95,8 @@ export class WorkspaceService implements FrontendApplicationContribution {
                 this.updateWorkspace();
             }
         });
-        this.fsPreferences.onPreferenceChanged(e => {
-            if (e.preferenceName === 'files.watcherExclude') {
+        this.fsPreferences.onPreferenceChanged(event => {
+            if (event.preferenceName === 'files.watcherExclude') {
                 this.refreshRootWatchers();
             }
         });