Control statements in assignment RHS

[stevepositiv]

Hi!

I noticed that syntax highlighting does not work properly for control statements used on the right-hand side of assignments.
I tried a small fix and for now it seems to work fine without unexpected side-effects.

$x = if ($a) { 1 } else { 2 }
$x = switch ($v) { 1 { 'one' } default { 'other' } }
$x = foreach ($i in 1..3) { $i * 2 }
$x = try { Get-Thing } catch { $null } 

My testing is limited, so I can't say anything definitive about edge cases or possible performance implications.

Here's my change:

--- PowerShell.sublime-syntax
+++ PowerShell.sublime-syntax
@@ -948,8 +948,11 @@
 
   in-assignment:
     - include: pop-end-of-command
     # INFO: Someday maybe we can nix the workflow stuff
     - include: workflow-execution-contexts
+    - include: conditionals
+    - include: loops
+    - include: exceptions
     - include: expressions
 
   redirection:

I'm not opening this as a PR because I don't know how to write syntax tests, and I'm unsure if this needs to be implemented differently as a proper fix.

Thanks for your work!

Best Regards
Steve

[michaelblyons]

Hi Steve, thanks for reporting!

Do you know if those conditionals, loops, and exceptions are available in any arbitrary expression?

Like can I do this with a try/catch?

if (2 * try { Get-Thing } catch { 4 } -gt $sentinel )
{ echo Foo }

[michaelblyons]

The OP's pattern for if is seen in the official docs in Assignment Operators:

You can also assign the value created by a statement to a variable, as in the following example:

$a = if ($b -lt 0) { 0 } else { $b }

This example assigns zero to the $a variable if the value of $b is less than zero. It assigns the value of $b to $a if the value of $b isn't less than zero.

And as an example, not itself documented at foreach:

      $filesToProcess = if ($_ -is [System.IO.FileSystemInfo]) {
        $_
      } else {
        Get-Item -Path $Path
      }

[michaelblyons]

I think I've found the real documentation for this at Statement values. These can get crazy:

$i = 1
$v = while ($i -le 5) {
    $i                   # $i is written to the pipeline
    if ($i -band 1) {
        "odd"            # conditionally written to the pipeline
    }
    ++$i                 # not written to the pipeline
}
# $v is object[], Length 8, value 1,"odd",2,3,"odd",4,5,"odd"

Does this mean that technically every statement is an expression? Including function and class definitions?

[michaelblyons]

As usual, PowerShell is more complicated.

# legal, $foo is 4 (= 0 + 4)
$foo =     try { Get-Thing } catch { 0 } + 4

# crashes
$foo = 4 + try { Get-Thing } catch { 0 }

# compiles, but unclear what $foo becomes
$foo = function Name { 5; Write-Host 6; return 7 }

I think we move exceptions, loops, flow, and conditionals from statements to expressions-without-commands and let the user sort it out if they try to add 4 + try {....