-debug requesting confirmation - debugging

Question

I have a simple script running in Powershell 3.0 :
# Testing write-debug
[CmdletBinding()]
param()
write-debug "Debug message"
Write-Output "General output"
When I run it without parameters, I get the desired output:
PS C:\scripts\Test> .\debugtest.ps1
General output
When I run it with the -debug parameter, Powershell asks me to confirm after printing the Debug message:
PS C:\scripts\Test> .\debugtest.ps1 -Debug
DEBUG: Debug message
Confirm
Continue with this operation?
[Y] Yes [A] Yes to All [H] Halt Command [S] Suspend [?] Help (default is "Y"):
General output
Why am I being asked to confirm? Shouldn't write-debug simply write the debug output and continue with the script?
Update: $DebugPreference is set to SilentlyContinue:
PS C:\scripts\Test> $DebugPreference
SilentlyContinue
PS C:\scripts\Test> .\debugtest.ps1 -Debug
DEBUG: Debug message
Confirm
Continue with this operation?
[Y] Yes [A] Yes to All [H] Halt Command [S] Suspend [?] Help (default is "Y"):
General output

Answer 1

It sounds like your $DebugPreference variable is set to 'Inquire'.
From Get-Help about_preference_variables:
$DebugPreference
------------------
Determines how Windows PowerShell responds to debugging messages
generated by a script, cmdlet or provider, or by a Write-Debug
command at the command line.
Some cmdlets display debugging messages, which are typically very
technical messages designed for programmers and technical support
professionals. By default, debugging messages are not displayed,
but you can display debugging messages by changing the value of
$DebugPreference.
You can also use the Debug common parameter of a cmdlet to display
or hide the debugging messages for a specific command. For more
information, type: "get-help about_commonparameters".
Valid values:
Stop: Displays the debug message and stops
executing. Writes an error to the console.
Inquire: Displays the debug message and asks you
whether you want to continue. Note that
adding the Debug common parameter to a
command--when the command is configured
to generate a debugging message--changes
the value of the $DebugPreference variable
to Inquire.
Continue: Displays the debug message and continues
with execution.
SilentlyContinue: No effect. The debug message is not
(Default) displayed and execution continues without
interruption.
Edit: -Debug is also a cmdlet Common Parameter, and by adding CmdletBinding(), it is also a Common Parameter of your script.
From Get-Help about_common_parameters:
COMMON PARAMETER DESCRIPTIONS
-Debug[:{$true | $false}]
Alias: db
Displays programmer-level detail about the operation performed by the
command. This parameter works only when the command generates
a debugging message. For example, this parameter works when a command
contains the Write-Debug cmdlet.
**The Debug parameter overrides the value of the $DebugPreference
variable for the current command, setting the value of $DebugPreference
to Inquire.** Because the default value of the $DebugPreference variable
is SilentlyContinue, debugging messages are not displayed by default.
Valid values:
$true (-Debug:$true). Has the same effect as -Debug.
$false (-Debug:$false). Suppresses the display of debugging
messages when the value of the $DebugPreference is not
SilentlyContinue (the default).

Answer 2

You can override $DebugPreference in the script:
[CmdletBinding()]
param()
Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'
if ($PSBoundParameters['Debug']) {
$DebugPreference = 'Continue'
}
Write-Output "General output"
Write-Debug "Debug message"

Answer 3

I think second parameter declarationof the following function can be added any function
function SetDebugPreference {
[CmdletBinding()]
Param(
[Parameter(
Mandatory=$true,
HelpMessage="Please enter for `$DebugPreference a value`n('SilentlyContinue','Continue' ,'Inquire' or 'Stop')",
ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true,
Position=0
)]
[ValidateSet("SilentlyContinue","Continue" ,"Inquire","Stop")]
[Alias("dbp","dbPref")]
[string]
$dbPreference,
[Parameter(
Mandatory=$false,
ValueFromPipelineByPropertyName=$true,
Position=1
)]
[ValidateSet("SilentlyContinue","Continue" ,"Inquire","Stop")]
[Alias("ldbp","ldbPref")]
[string]
$LocalDebugPreference="Continue"
)
Begin {
Write-Verbose ("Local DebugPreference: " + $DebugPreference)
$DebugPreference=$LocalDebugPreference
Write-Verbose ("Local DebugPreference set: " + $LocalDebugPreference)
Write-Debug "Local debug test"
}
Process {
Write-Verbose ("Global DebugPreference: " + $Global:DebugPreference)
$Global:DebugPreference=$dbPreference
Write-Verbose ("Global DebugPreference set: " + $Global:DebugPreference)
}
}