fix #3714 - jupyter2: support "from x import _" tab completion (more precisely -- align our completion heuristic with JupyterLab's)

- also I made the sorting of results match up

Author: williamstein

src/packages/frontend/jupyter/codemirror-editor.tsx

@@ -27,6 +27,7 @@ import { SAVE_DEBOUNCE_MS } from "../frame-editors/code-editor/const";
 import { Complete, Actions as CompleteActions } from "./complete";
 import { Cursors } from "./cursors";
 import { Position } from "./insert-cell/types";
+import { is_whitespace } from "@cocalc/util/misc";
 
 // We cache a little info about each Codemirror editor we make here,
 // so we can restore it when we make the same one again.  Due to
@@ -551,7 +552,7 @@ export const CodeMirrorEditor: React.FC<CodeMirrorEditorProps> = ({
   function whitespace_before_cursor(): boolean {
     if (cm.current == null) return false;
     const cur = cm.current.getCursor();
-    return cur.ch === 0 || /\s/.test(cm.current.getLine(cur.line)[cur.ch - 1]);
+    return is_whitespace(cm.current.getLine(cur.line).slice(0, cur.ch));
   }
 
   async function tab_nothing_selected(): Promise<void> {

src/packages/jupyter/redux/actions.ts

@@ -1064,6 +1064,7 @@ export abstract class JupyterActions extends Actions<JupyterStoreState> {
   };
 
   undo = (): void => {
+    console.trace("jupyter redux undo");
     if (this.syncdb != null) {
       this.syncdb.undo();
     }
@@ -1702,7 +1703,16 @@ export abstract class JupyterActions extends Actions<JupyterStoreState> {
     }
     // For some reason, sometimes complete.matches are not unique, which is annoying/confusing,
     // and breaks an assumption in our react code too.
-    complete.matches = Array.from(new Set(complete.matches)).sort();
+    complete.matches = Array.from(new Set(complete.matches));
+    // sort in a way that matches how JupyterLab sorts completions, which
+    // is case insensitive with % magics at the bottom
+    complete.matches.sort((x, y) => {
+      const c = misc.cmp(getCompletionGroup(x), getCompletionGroup(y));
+      if (c) {
+        return c;
+      }
+      return misc.cmp(x.toLowerCase(), y.toLowerCase());
+    });
     const i_complete = immutable.fromJS(complete);
     if (complete.matches && complete.matches.length === 1 && id != null) {
       // special case -- a unique completion and we know id of cell in which completing is given.
@@ -2742,3 +2752,14 @@ function bounded_integer(n: any, min: any, max: any, def: any) {
   }
   return n;
 }
+
+function getCompletionGroup(x: string): number {
+  switch (x[0]) {
+    case "_":
+      return 1;
+    case "%":
+      return 2;
+    default:
+      return 0;
+  }
+}