'kubectl patch' works on Linux Bash but not in Windows Powershell ISE

For detailed and very useful background, see the answer by mklement0

After much frustration, I have decided to list all variants of quote escaping that I've tried, and came up with one more, which suddenly worked! So, sharing it here:

kubectl patch deployment wapi-backend-d1 --patch '{\"spec\": {\"template\": {\"metadata\": {\"labels\": {\"date\": \"test123\"}}}}}'

This is how to use kubectl patch with Powershell

Also, of note: I was actually trying to patch it with a timestamp to trigger a rolling update without changing tags of container images (so set image would not help me).

When you try to put your JSON into a variable and then call kubectl patch with a variable, you get into trouble with escaping again. This is what I ended up with:

$patchRequest = @{
    spec = @{
        template = @{
            metadata = @{
                labels = @{
                    date = ((((Get-Date -Format o)).replace(':','-').replace('+','_')))
                }
            }
        }
    }
}
$patchJson = ((ConvertTo-Json -InputObject $patchRequest -Compress -Depth 10))
$patchJson = $patchJson.replace('"','\"')
kubectl patch deployment wapi-backend-d1 --patch $patchJson

You've found the right solution in your own answer, but let me try to break it down conceptually:

Embedding " (double quotes) in string arguments passed to external programs:

• (a) First - sensibly and unavoidably - you need to satisfy PowerShell's syntax requirements with respect to embedding " chars. in quoted strings.

• (b) Then - and this step shouldn't be necessary - you need to \-escape embedded " chars. that you want external programs to see.

  • This is a longstanding, irksome bug present up to at least PowerShell 7.2, which may get fixed in 7.3 - see this answer.

Re (a), you have the following options:

• '...'-quoting (single-quoting), inside of which you can use " as-is:

  • '{ "spec": "none" }'
  • Everything inside '...' is taken literally - no expansion (interpolation) takes place.

• "..."-quoting (double-quoting), inside of which you can use `" or "" to embed " chars:

  • "{ `"spec`": `"none`" }" - ` is PowerShell's general escape char.
  • "{ ""spec"": ""none"" }" - "-specific escaping (doubling)
  • The content of "..." is subject to expansion (interpolation), meaning that you can reference variables ($var) or subexpressions ($(1 + 2)) inside such strings, which PowerShell replaces with their values - see this answer for more about PowerShell's expandable strings.

If you're passing such a string to other PowerShell commands (cmdlets, functions, or scripts), no further action is needed; e.g.:

PS> Write-Output '3" of rain'
3" of rain

Re (b) - i.e. to pass such strings to external programs - you additionally need to \-escape the embedded " chars.:

• Applying manual escaping to the examples above:

  • '{ \"spec\": \"none\" }'
  • "{ \`"spec\`": \`"none\`" }"
  • "{ \""spec\"": \""none\"" }"

• Applying the escaping programmatically to a preexisting string:

  • Replace verbatim " with verbatim \", as well as any preexisting, immediately preceding \ with \\:

    • $str = '3" of rain'; $escapedStr = $str -replace '([\\]*)"', '$1$1\"'

    • That is, for an external program to ultimately see value 3" of rain verbatim, you must pass literal value 3\" of rain from PowerShell. This \-escaping is something that PowerShell, as a shell, should do automatically behind the scenes, but currently doesn't.

• There's an additional bug in Windows PowerShell - since fixed in PowerShell Core - that mishandles strings with unbalanced embedded " chars. if a " is part of the first word:

  • E.g., the above techniques do NOT work with literal values such as 3" of rain; that is, escaping this as '3\" of rain' does not work as expected - instead, you must use the following monstrosity: `"3\`" of rain`", which is technically a series of separate, unquoted arguments, which means that (a) multiple spaces between the words of the strings aren't supported (they are collapsed to a single space) and (b) PowerShell metacharacters such as & < > $ & | @ { must be individually `-escaped.
  • Note that the bug surfaces only if the " is part of the first word in the value, and only if that first word is not preceded by whitespace (though arguments with leading whitespace are rarely useful); e.g., '3 \" of rain' would again work, because the unbalanced " is not part of the first word.

Example:

The following uses choice.exe as an example external program, because it can be repurposed (via options /d Y /t 0) to merely echo the prompt string it is given, which shows how it received the string passed from PowerShell:

& {
  # Note: For preview versions of v7.2, deactivate the experimental
  #       feature that fixes the problem, so as to show the original problem.   
  $PSNativeCommandArgumentPassing = 'Legacy'

  # Use manual \-escaping to pass what should be received as
  # verbatim { "spec": "none" } to an external program.
  choice /m '{ \"spec\": \"none\" }' /d Y /t 0
}

The above outputs { "spec": "none" } [Y,N]?Y, showing that the manually escaped " chars. were received as verbatim " chars. by the external program.