Fix :p[ut] command neovim capability and subparser (#5063)

Enables neovim capability and fixes arg parsing for the `:p[ut]` command. Apparently the put command allows no whitespace between the command name and the register name, so commands like `:put"` are perfectly valid. I've added some subparser tests to document this.

Fixes #5052
Fixes #5090

src/cmd_line/commands/put.ts

@@ -27,6 +27,10 @@ export class PutExCommand extends node.CommandBase {
     return this._arguments;
   }
 
+  public neovimCapable(): boolean {
+    return true;
+  }
+
   async doPut(vimState: VimState, position: Position) {
     const registerName = this.arguments.register || (configuration.useSystemClipboard ? '*' : '"');
     vimState.recordedState.registerName = registerName;

src/cmd_line/subparsers/put.ts

@@ -1,5 +1,4 @@
 import { PutExCommand, IPutCommandArguments } from '../commands/put';
-import { ErrorCode, VimError } from '../../error';
 import { Scanner } from '../scanner';
 
 export function parsePutExCommandArgs(args: string): PutExCommand {
@@ -14,8 +13,8 @@ export function parsePutExCommandArgs(args: string): PutExCommand {
   if (c === '!') {
     scannedArgs.bang = true;
     scanner.ignore();
-  } else if (c !== ' ') {
-    throw VimError.fromCode(ErrorCode.TrailingCharacters);
+  } else {
+    scanner.backup();
   }
   scanner.skipWhiteSpace();
 

test/cmd_line/subparser.put.test.ts

@@ -0,0 +1,34 @@
+import * as assert from 'assert';
+import { commandParsers } from '../../src/cmd_line/subparser';
+
+suite(':put args parser', () => {
+  test('can parse empty args', () => {
+    const args = commandParsers.put.parser('');
+    assert.strictEqual(args.arguments.bang, undefined);
+    assert.strictEqual(args.arguments.register, undefined);
+  });
+
+  test('can parse !', () => {
+    const args = commandParsers.put.parser('!');
+    assert.strictEqual(args.arguments.bang, true);
+    assert.strictEqual(args.arguments.range, undefined);
+  });
+
+  test('can parse register', () => {
+    const args = commandParsers.put.parser(' *');
+    assert.strictEqual(args.arguments.bang, undefined);
+    assert.strictEqual(args.arguments.register, '*');
+  });
+
+  test('can parse register with no whitespace', () => {
+    const args = commandParsers.put.parser('*');
+    assert.strictEqual(args.arguments.bang, undefined);
+    assert.strictEqual(args.arguments.register, '*');
+  });
+
+  test('can parse register with no whitespace and !', () => {
+    const args = commandParsers.put.parser('!*');
+    assert.strictEqual(args.arguments.bang, true);
+    assert.strictEqual(args.arguments.register, '*');
+  });
+});