Add --help option to Dart VM shell. And all dart executables.

[whesse]

I can never remember the name of the --print-flags option, and there is no single flag-definitions file where all the flags are declared.

[iposva-google]

I don't think adding an extra flag would really help here, actually it would make matters worse in my opinion. Instead the dart binary should give a bit more information in its PrintUsage() function.

[whesse]

Issue #1188 has been merged into this issue.

[iposva-google]

Set owner to @iposva-google.
Added Accepted label.

[sethladd]

--help is a fairly standard convention. It would be very useful if --help worked, and printed the available command line flags.

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cc @sgmitrovic.

[sethladd]

dart2js has a --help now.

[alan-knight]

Yes, I would never have thought of --print-flags

[DartBot]

This comment was originally written by jjinux...@google.com

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I stumbled across this bug because "dart --help" didn't give me what I was looking for, namely --enable_type_checks.

[DartBot]

This comment was originally written by jjinux...@google.com

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Since this is so easy to fix, the priority should probably be higher.

[sethladd]

Any updates on this? Could we get an --help alias to --print-flags before the book goes out? Thanks!

[ghost]

I think --help should list a subset of flags dumped by --print-flags, flags that should be used by external users, not the flags used by developers only.

[DartBot]

This comment was originally written by jminer...@gmail.com

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I use Windows and would like a couple aliases for --help. On Windows, /? seems to be the standard flag for help. I think at least the first two of these should be supported, and maybe all of them:
/?
-?
/h
-h
/help
-help

[larsbak]

The current help text for the VM is insufficient:
$ dart
dart [<vm-flags>] <dart-script-file> [<dart-options>]

Before M1 we need to:
  - Improve discoverability of flags.
  - Make simple short flags for common operations.
  - Harmonize if possible with the dart2js flags.
//Lars

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Added this to the M1 milestone.
Removed Priority-Low label.
Added Priority-Medium label.

[iposva-google]

The only flags that we currently have in the VM that definitely make sense in the dart2js context are:
--enable-asserts
--enable-type-checks
--enable-checked-mode (this one controls the value of the two above in a single flag)

--help (will be added to print explanations to the above flags)
--ignore-unrecognized-flags

Other flags which could fall into dart2js/vm harmonification, but we need to clarify this:
--package-root
--print-flags

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cc @kasperl.

[kasperl]

Here are the flags that we're exposing to users of dart2js for inspiration:

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$ dart2js -h
Usage: dart2js [options] dartfile

Compiles Dart to JavaScript.

Common options:
  -o<file> Generate the output into <file>.
  -c Insert runtime type checks and enable assertions (checked mode).
  -h Display this message (add -v for information about all options).

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$ dart2js -h -v
Usage: dart2js [options] dartfile

Compiles Dart to JavaScript.

Supported options:
  -o<file>, --out=<file>
    Generate the output into <file>.

  -c, --enable-checked-mode, --checked
    Insert runtime type checks and enable assertions (checked mode).

  -h, /h, /?, --help
    Display this message (add -v for information about all options).

  -v, --verbose
    Display verbose information.

  -p<path>, --package-root=<path>
    Where to find packages, that is, "package:..." imports.

  --suppress-warnings
    Do not display any warnings.

  --no-colors
    Do not add colors to diagnostic messages.

The following options are only used for compiler development and may
be removed in a future version:

  --output-type=dart
    Output Dart code instead of JavaScript.

  --throw-on-error
    Throw an exception if a compile-time error is detected.

  --library-root=<directory>
    Where to find the Dart platform libraries.

  --allow-mock-compilation
    Do not generate a call to main if either of the following
    libraries are used: dart:dom, dart:html dart:io.

[DartBot]

This comment was originally written by Ruper...@gmail.com

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Is this something a frustrated^W er, motivated community member could fix? (along with Issue #3379)

[iposva-google]

Fixed the standalone Dart VM binary with https://chromiumcodereview.appspot.com/10979006/

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Added Fixed label.

[munificent]

Hooray!