F# Parameters in Custom step template

Legacy Execution
1

I have a Custom Step Template with script source set to source code, with the script in f# but I cannot find anyway to get the parameters passed through. I have a parameter setup called Site, which displays in the parameters tab as #{Site}

If I do (which is what you get when you pick the variable via the picker tool)
System.Console.WriteLine(Site)
Script.fsx(7,26): error FS0039: The value or constructor ‘Site’ is not defined

System.Console.WriteLine(#{Site})
Outputs ‘#{Site}’ i.e. just the literal string

System.Console.WriteLine(Octopus.Parameters[“Site”])
Script.fsx(3,34): error FS0039: The value, constructor, namespace or type ‘Parameters’ is not defined

What is the syntax to pass parameters into an fsharp script?

2

Hi Ian, thanks for reaching out.

You can find more information on using variables in F# scripts at https://octopus.com/docs/deploying-applications/custom-scripts#Customscripts-Variables.

For example:

System.Console.WriteLine("#{Site}")
System.Console.WriteLine(Octopus.findVariable "Site")

Regards
Matt C

3

Hi,

Thanks for you help, I’ve managed to get this working but just a couple of things to note, as you seem to be an employee:

I’ve just tested on Octopus 3.14.1592.

The first example:
System.Console.WriteLine("#{Site}")
Just outputs the literal ‘#{Site}’ rather than the value of the variable. So I may have found a bug. I’ve exported my step and attached it to help with any replication.

The second example:
System.Console.WriteLine(Octopus.findVariable “Site”)
However, this function is not mentioned in the linked documentation, so would be good to update it to include this.

Cheers,

Ian.

exported.txt (990 Bytes)

4

*The above should say the second example works

5

Hi Ian. Thanks for the feedback on the docs.

The literal #{Site} will be printed if the variable is not defined or available. In your test System.Console.WriteLine("#{Site}") printed the literal while System.Console.WriteLine(Octopus.findVariable "Site") printed the variable with no other changes to the script? If so that is definitely a bug. In that case could you also attach a screenshot of the variables page?

Regards
Matt C

6

Hi,

I deleted my original test, so have created another replicating the issue with screenshots of the input and output.

Cheers,

Ian.

export.txt (1 KB)

Input.png
Input.png1698×741 44.1 KB

Output.png
Output.png1900×490 25.8 KB

7

Hi Ian. You are correct - the #{Site} format doesn’t work for step template parameters. It does work for project variables, but for consistency you can use Octopus.tryFindVariable, Octopus.findVariable or Octopus.findVariableOrDefault.

I’ve included some examples below.

// It's a good idea to copy the value into a variable to avoid quoting issues

// tryFindVariable : name:string -> string option
let connectionString = Octopus.tryFindVariable "MyApp.ConnectionString"
match connectionString with
    | Some x -> printf "Connection string is: %s" x
    | None -> printf "Connection string not found"
 
// Or one of the simplified versions

// Throws KeyNotFoundException when variable does not exist
// findVariable : name:string -> string
let connectionString = Octopus.findVariable "MyApp.ConnectionString"

// Returns default value when variable does not exist
// findVariableOrDefault : defaultValue:string -> name:string -> string
let connectionString = Octopus.findVariableOrDefault "Default Value" "MyApp.ConnectionString"

Regards
Matt C