[ts-command-line] Parameters in CommandLineParser onExecute are undefined

[Petah]

Summary

I followed the example in the readme, trying to add a --verbose parameter to all actions, but in the onExecute method this._verbose is undefined.

Repro steps

import { CommandLineAction, CommandLineChoiceParameter, CommandLineFlagParameter, CommandLineParser } from '@rushstack/ts-command-line';

export class PushAction extends CommandLineAction {
    private _force!: CommandLineFlagParameter;
    private _protocol!: CommandLineChoiceParameter;

    public constructor() {
        super({
            actionName: 'push',
            summary: 'Pushes a widget to the service',
            documentation: 'Here we provide a longer description of how our action works.'
        });
    }

    protected onExecute(): Promise<void> { // abstract
        // return BusinessLogic.doTheWork(this._force.value, this._protocol.value || "(none)");
        console.log('PushAction.onExecute', this._force.value, this._protocol.value);
        return Promise.resolve();
    }

    protected onDefineParameters(): void { // abstract
        this._force = this.defineFlagParameter({
            parameterLongName: '--force',
            parameterShortName: '-f',
            description: 'Push and overwrite any existing state'
        });

        this._protocol = this.defineChoiceParameter({
            parameterLongName: '--protocol',
            description: 'Specify the protocol to use',
            alternatives: ['ftp', 'webdav', 'scp'],
            environmentVariable: 'WIDGET_PROTOCOL',
            defaultValue: 'scp'
        });
    }
}

export class WidgetCommandLine extends CommandLineParser {
    private _verbose!: CommandLineFlagParameter;

    public constructor() {
        super({
            toolFilename: 'widget',
            toolDescription: 'The "widget" tool is a code sample for using the @rushstack/ts-command-line library.',
        });

        this.addAction(new PushAction());
    }

    protected onDefineParameters(): void { // abstract
        this._verbose = this.defineFlagParameter({
            parameterLongName: '--verbose',
            parameterShortName: '-v',
            description: 'Show extra logging detail',
        });
    }

    protected onExecute(): Promise<void> { // override
        console.log('WidgetCommandLine.onExecute', this._verbose);
        return super.onExecute();
    }
}

const commandLine: WidgetCommandLine = new WidgetCommandLine();
commandLine.execute();

Expected result:

WidgetCommandLine.onExecute [the verbose parameter object]
PushAction.onExecute true scp

Actual result:

WidgetCommandLine.onExecute undefined
PushAction.onExecute true scp

Details

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
Package name:	@rushstack/ts-command-line
Package version?	4.19.5
Operating system?	Mac
Would you consider contributing a PR?	No
Node.js version (node -v)?	v21.7.1

[iclanton]

I'm not getting a repro of this issue. I've created a repo here with your example and invited you to it: https://github.com/iclanton/rushstack-4708-repro. Can you update that with your repro?

This is the output I get from various commands (I've run this on Windows and Linux, but not Mac):

> node lib\test
usage: widget [-h] [-v] <command> ...

The "widget" tool is a code sample for using the @rushstack/ts-command-line
library.

Positional arguments:
  <command>
    push         Pushes a widget to the service

Optional arguments:
  -h, --help     Show this help message and exit.
  -v, --verbose  Show extra logging detail

For detailed help about a specific command, use: widget <command> -h

> node lib\test push
WidgetCommandLine.onExecute CommandLineFlagParameter {
  longName: '--verbose',
  _shortNameValue: '-v',
  parameterGroup: undefined,
  parameterScope: undefined,
  description: 'Show extra logging detail',
  required: false,
  environmentVariable: undefined,
  undocumentedSynonyms: undefined,
  allowNonStandardEnvironmentVariableNames: undefined,
  _value: false,
  kind: 1,
  _parserKey: 'key_0'
}
PushAction.onExecute false scp

[Petah]

Hmm, it seems to be an issue with my tsconfig.json. Not sure if thats a bug, or just incorrect setup on my part, but I have updated the tsconfig.json in that repo.

> node lib/test.js --verbose push --force
WidgetCommandLine.onExecute undefined
PushAction.onExecute true scp
> ./node_modules/.bin/ts-node src/test.ts --verbose push --force
WidgetCommandLine.onExecute undefined
PushAction.onExecute true scp

[iclanton]

This issue is the "target": "es2022" compiler option. See TypeScript docs here: https://www.typescriptlang.org/docs/handbook/2/classes.html#initialization-order

Comparing the TypeScript compiler output for es2021 vs es2022:

class WidgetCommandLine extends ts_command_line_1.CommandLineParser {
+    _verbose;
    constructor() {
        super({
            toolFilename: "widget",
            toolDescription: 'The "widget" tool is a code sample for using the @rushstack/ts-command-line library.',
        });
        this.addAction(new PushAction());
    }
    onDefineParameters() {
        // abstract
        this._verbose = this.defineFlagParameter({
            parameterLongName: "--verbose",
            parameterShortName: "-v",
            description: "Show extra logging detail",
        });
    }
    onExecute() {
        // override
        console.log("WidgetCommandLine.onExecute", this._verbose);
        return super.onExecute();
    }
}

Notice that the _verbose field is now emitted in the class. The onDefineParameters function is called by the CommandLineParser's constructor, which causes the problem. From the TypeScript docs, the initialization order is:

1. The base class fields are initialized - _verbose is not defined at this point
2. The base class constructor runs - **onDefineParameters is called, and _verbose is now defined as expected`
3. The derived class fields are initialized - the _verbose field initializer, emitted by TS in >=ES2022, is executed and redefines _verbose as undefined
4. The derived class constructor runs - other stuff happens, like the this.addAction(new PushAction()); line

To fix this issue, target <es2022, or move the parameter declarations into the WidgetCommandLine constructor, like ths:

export class WidgetCommandLine extends CommandLineParser {
-  private _verbose!: CommandLineFlagParameter;
+  private _verbose: CommandLineFlagParameter;

  public constructor() {
    super({
      toolFilename: "widget",
      toolDescription:
        'The "widget" tool is a code sample for using the @rushstack/ts-command-line library.',
    });

    this.addAction(new PushAction());
-  }
-
-  protected onDefineParameters(): void {
-    // abstract
+
+  // define parameters
    this._verbose = this.defineFlagParameter({
      parameterLongName: "--verbose",
      parameterShortName: "-v",
      description: "Show extra logging detail",
    });
  }

  protected onExecute(): Promise<void> {
    // override
    console.log("WidgetCommandLine.onExecute", this._verbose);
    return super.onExecute();
  }
}

We should probably consider removing the onDefineParameters function and, instead, explicitly recommending that users of ts-command-line initialize parameters directly in the constructor. This allows the removal of the non-null assertion on the _verbose field.

[iclanton]

Closing this out, since it seems like we've figured out the issue.