Pipeline chain operators #9849

rjmholt · 2019-06-07T01:10:55Z

This PR is specified by PowerShell/PowerShell-RFC#192

PR Summary

Resolves #3241.

Implements && and ||.

A statement like cmd1 && cmd2 should behave like cmd1; if ($?) { cmd2 }.

After discussion with the @PowerShell/powershell-committee, this feature has the following charateristics:

cmd1 && cmd2 behaves like cmd1; if ($?) { cmd2 }
cmd1 || cmd2 behaves like cmd1; if (-not $?) { cmd2 }
cmd1 && cmd2 && cmd3 is left associative: [cmd1 && cmd2] && cmd3
No control flow statements in pipeline chains; only pipelines. Control flow statements are still possible with subexpressions in pipelines (cmd1 && $(break)). These were taken out due to the inconsitencies they posed at a grammatical, data structure and semantic level.
Assignment is consistent with other assignment in PowerShell, so that a script terminating error will not result in a partial assignment, but a pipeline-terminating error will.
This syntax is available as the PSPipelineChainOperators experimental feature

PR Checklist

src/System.Management.Automation/engine/parser/AstVisitor.cs

daxian-dbw · 2019-06-11T15:26:10Z

The && and || operators allow statements for both operands in bash. Why don't we do the same in PowerShell?

rjmholt · 2019-06-11T17:44:10Z

Discussed this offline with @daxian-dbw. We've decided to get rid of the subordinate statements and move assignment up to the whole chain (so no $x = cmd1 && $y = cmd2). I'll try to rework this today or tomorrow

stereokai · 2019-06-12T07:39:57Z

@rjmholt Can you explain the reasoning in this PR thread?

rjmholt · 2019-06-12T15:43:22Z

Can you explain the reasoning in this PR thread?

I've discussed again with @daxian-dbw and we agreed this is now best served by an RFC. When that RFC is accepted, I'll make the desired changes in this branch

rjmholt · 2019-06-12T20:48:07Z

Please see PowerShell/PowerShell-RFC#192

stereokai · 2019-06-13T11:57:18Z

Excellent, thanks

src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs

This reverts commit 3e374f9.

build.psm1

rjmholt · 2019-10-17T21:54:28Z

🎉

TylerLeonhardt · 2019-10-18T08:02:07Z

🎉🎉🎉 Nice!

Graham-Beer · 2019-10-18T09:37:54Z

This is awesome! Looking forward to having a look in PS7 preview 5!

The `&&` syntax is not supported in PowerShell. See PowerShell/PowerShell#9849.

The `&&` syntax is not supported in PowerShell (yet). See PowerShell/PowerShell#9849.

…uage (PowerShell#9849)

PowerShell can't be relied upon to have `&&`. PowerShell/PowerShell#9849

rjmholt requested review from SteveL-MSFT and daxian-dbw June 7, 2019 01:11

SeeminglyScience reviewed < 8000 span class="color-fg-muted"> Jun 7, 2019

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src/System.Management.Automation/engine/parser/AstVisitor.cs Outdated Show resolved Hide resolved

rjmholt force-pushed the bash-operators branch from bb535bc to 2e65e5f Compare June 10, 2019 16:47

PoshChan reviewed Jun 19, 2019

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