fix(mongosh-repl): fix REPL command completion MONGOSH-778 (#891)

Author: addaleax

packages/cli-repl/src/mongosh-repl.spec.ts

@@ -352,6 +352,20 @@ describe('MongoshNodeRepl', () => {
         await tick();
         expect(output).to.include('somelongvariable');
       });
+      it('autocompletes partial repl commands', async() => {
+        input.write('.e');
+        await tabtab();
+        await tick();
+        expect(output).to.include('editor');
+        expect(output).to.include('exit');
+      });
+      it('autocompletes full repl commands', async() => {
+        input.write('.ed');
+        await tabtab();
+        await tick();
+        expect(output).to.include('.editor');
+        expect(output).not.to.include('exit');
+      });
       it('autocompletion during .editor does not reset the prompt', async() => {
         input.write('.editor\n');
         await tick();

packages/cli-repl/src/mongosh-repl.ts

@@ -189,7 +189,7 @@ class MongoshNodeRepl implements EvaluationListener {
         this.insideAutoCompleteOrGetPrompt = true;
         try {
           // Merge the results from the repl completer and the mongosh completer.
-          const [ [replResults], [mongoshResults,, mongoshResultsExclusive] ] = await Promise.all([
+          const [ [replResults, replOrig], [mongoshResults,, mongoshResultsExclusive] ] = await Promise.all([
             (async() => await origReplCompleter(text) || [[]])(),
             (async() => await mongoshCompleter(text))()
           ]);
@@ -205,7 +205,10 @@ class MongoshNodeRepl implements EvaluationListener {
           // Remove duplicates, because shell API methods might otherwise show
           // up in both completions.
           const deduped = [...new Set([...replResults, ...mongoshResults])];
-          return [deduped, text];
+
+          // Use the REPL completer's original text when available, because that
+          // makes a difference for completion of REPL commands like `.editor`.
+          return [deduped, replOrig ?? text];
         } finally {
           this.insideAutoCompleteOrGetPrompt = false;
         }