Enable strict null checks and other strict settings

packages/_example-extractor/src/api.spec.ts

@@ -37,7 +37,7 @@ describe('The foo extractor', () => {
   test.each(Object.entries(FIXTURES))(
     '%s',
     (_: string, expected: IExtractedCode) => {
-      const extracted = extractor.extract_foreign_code(expected.host_code);
+      const extracted = extractor.extract_foreign_code(expected.host_code!);
       expect(extracted).to.have.length(1);
       expect(extracted[0]).to.deep.equal(expected);
     }

packages/code-jumpers/src/history.ts

@@ -30,7 +30,7 @@ export class JumpHistory {
     this.jump_history.push(JSON.stringify(position));
   }
 
-  recollect(): IGlobalPosition {
+  recollect(): IGlobalPosition | undefined {
     this.ensure_history_is_ready();
     if (this.jump_history.length === 0) {
       return;

packages/code-jumpers/src/jumpers/fileeditor.ts

@@ -36,7 +36,7 @@ export class FileEditorJumper extends CodeJumper {
 
     // TODO: this is common
     // place cursor in the line with the definition
-    let position = this.editor.editor.getPositionAt(token.offset);
+    let position = this.editor.editor.getPositionAt(token.offset)!;
     this.editor.editor.setSelection({ start: position, end: position });
     this.editor.editor.focus();
   }
@@ -58,7 +58,7 @@ export class FileEditorJumper extends CodeJumper {
   getCurrentPosition(): IGlobalPosition {
     let position = this.editor.editor.getCursorPosition();
     return {
-      editor_index: null,
+      editor_index: 0,
       line: position.line,
       column: position.column,
       contents_path: this.editor.context.path,

packages/code-jumpers/src/jumpers/jumper.ts

@@ -69,12 +69,16 @@ export abstract class CodeJumper {
     let document_widget = this.document_manager.openOrReveal(
       position.contents_path
     );
+    if (!document_widget) {
+      console.log('Widget failed to open for jump');
+      return;
+    }
     let is_symlink = position.is_symlink;
 
     document_widget.revealed
       .then(() => {
         this.go_to_position(
-          document_widget,
+          document_widget!,
           position.contents_path.endsWith('.ipynb') ? 'notebook' : 'fileeditor',
           position.column,
           position.line,
@@ -83,7 +87,7 @@ export abstract class CodeJumper {
 
         // protect external files from accidental edition
         if (is_symlink) {
-          this.protectFromAccidentalEditing(document_widget);
+          this.protectFromAccidentalEditing(document_widget!);
         }
       })
       .catch(console.warn);

packages/code-jumpers/src/jumpers/notebook.ts

@@ -19,7 +19,7 @@ export class NotebookJumper extends CodeJumper {
     super();
     this.widget = notebook_widget;
     this.notebook = notebook_widget.content;
-    this.history = new JumpHistory(this.notebook.model.modelDB);
+    this.history = new JumpHistory(this.notebook.model!.modelDB);
     this.document_manager = document_manager;
   }
 
@@ -33,15 +33,15 @@ export class NotebookJumper extends CodeJumper {
     // Prevents event propagation issues
     setTimeout(() => {
       this.notebook.deselectAll();
-      this.notebook.activeCellIndex = index;
+      this.notebook.activeCellIndex = index!;
       _ensureFocus(this.notebook);
       this.notebook.mode = 'edit';
 
       // find out offset for the element
-      let activeEditor = this.notebook.activeCell.editor;
+      let activeEditor = this.notebook.activeCell!.editor;
 
       // place cursor in the line with the definition
-      let position = activeEditor.getPositionAt(token.offset);
+      let position = activeEditor.getPositionAt(token.offset)!;
       activeEditor.setSelection({ start: position, end: position });
     }, 0);
   }

packages/code-jumpers/src/positions.ts

@@ -6,14 +6,15 @@ export interface ILocalPosition {
    */
   token: CodeEditor.IToken;
   /**
-   * Optional number identifying the cell in a notebook
+   * Optional number identifying the cell in a notebook.
+   * 0 in widgets with single editor
    */
-  index?: number;
+  index: number;
 }
 
 export interface IGlobalPosition {
   /**
-   * In notebooks, the index of the target editor
+   * In notebooks, the index of the target editor; 0 in widgets with single editor.
    */
   editor_index: number;
 

packages/completion-theme/src/about.tsx

@@ -69,7 +69,7 @@ export function render_themes_list(
   trans: TranslationBundle,
   props: {
     themes: ICompletionTheme[];
-    current: ICompletionTheme;
+    current: ICompletionTheme | null;
     get_set: IconSetGetter;
   }
 ): React.ReactElement {

packages/completion-theme/src/index.ts

@@ -23,7 +23,7 @@ import {
 export class CompletionThemeManager implements ILSPCompletionThemeManager {
   protected current_icons: Map<string, LabIcon>;
   protected themes: Map<string, ICompletionTheme>;
-  private current_theme_id: string;
+  private current_theme_id: string | null = null;
   private icons_cache: Map<string, LabIcon>;
   private icon_overrides: Map<string, CompletionItemKindStrings>;
   private trans: TranslationBundle;
@@ -50,17 +50,17 @@ export class CompletionThemeManager implements ILSPCompletionThemeManager {
     const dark_mode_and_dark_supported =
       !this.is_theme_light() && typeof icons_sets.dark !== 'undefined';
     const set: ICompletionIconSet = dark_mode_and_dark_supported
-      ? icons_sets.dark
+      ? icons_sets.dark!
       : icons_sets.light;
     const icons: Map<keyof ICompletionIconSet, LabIcon> = new Map();
-    let options = this.current_theme.icons.options || {};
+    let options = this.current_theme?.icons?.options || {};
     const mode = this.is_theme_light() ? 'light' : 'dark';
     for (let [completion_kind, svg] of Object.entries(set)) {
       let name =
         'lsp:' + theme.id + '-' + completion_kind.toLowerCase() + '-' + mode;
       let icon: LabIcon;
       if (this.icons_cache.has(name)) {
-        icon = this.icons_cache.get(name);
+        icon = this.icons_cache.get(name)!;
       } else {
         icon = new LabIcon({
           name: name,
@@ -83,19 +83,19 @@ export class CompletionThemeManager implements ILSPCompletionThemeManager {
     this.current_icons = this.get_iconset(this.current_theme);
   }
 
-  get_icon(type: string): LabIcon {
+  get_icon(type: string): LabIcon | null {
     if (this.current_theme === null) {
       return null;
     }
     if (type) {
       if (this.icon_overrides.has(type.toLowerCase())) {
-        type = this.icon_overrides.get(type.toLowerCase());
+        type = this.icon_overrides.get(type.toLowerCase())!;
       }
       type =
         type.substring(0, 1).toUpperCase() + type.substring(1).toLowerCase();
     }
     if (this.current_icons.has(type)) {
-      return this.current_icons.get(type);
+      return this.current_icons.get(type)!;
     }
 
     if (type === KernelKind) {
@@ -112,7 +112,7 @@ export class CompletionThemeManager implements ILSPCompletionThemeManager {
     if (this.current_theme_id) {
       document.body.classList.remove(this.current_theme_class);
     }
-    if (!this.themes.has(id)) {
+    if (id && !this.themes.has(id)) {
       console.warn(
         `[LSP][Completer] Icons theme ${id} cannot be set yet (it may be loaded later).`
       );
@@ -123,8 +123,8 @@ export class CompletionThemeManager implements ILSPCompletionThemeManager {
   }
 
   protected get current_theme(): ICompletionTheme | null {
-    if (this.themes.has(this.current_theme_id)) {
-      return this.themes.get(this.current_theme_id);
+    if (this.current_theme_id && this.themes.has(this.current_theme_id)) {
+      return this.themes.get(this.current_theme_id)!;
     }
     return null;
   }

packages/jupyterlab-lsp/src/adapter_manager.ts

@@ -132,9 +132,9 @@ export class WidgetAdapterManager implements ILSPAdapterManager {
     this.refreshAdapterFromCurrentWidget();
   }
 
-  isAnyActive() {
+  isAnyActive(): boolean {
     return (
-      this.shell.currentWidget &&
+      this.shell.currentWidget !== null &&
       this.adapterTypes.some(type => type.tracker.currentWidget) &&
       this.adapterTypes.some(
         type => type.tracker.currentWidget == this.shell.currentWidget