Converting From Yaml but the Input is a variable with a file content about powershell-yaml HOT 3 CLOSED

So 20 minutes after I posted this issue I have thrown a triple chasing some solution and I found it, I get the file content at the same time as I convert the variable from yaml to a hashtable.

from powershell-yaml.

A bit of context to what happened in the first one. When you use Get-Content without the -Raw parameter, you get an array of objects. Essentially, an array of lines inside the yaml file.

When you use the -Raw flag, all the contents of the file is read at once as a raw string.

The powershell-yaml module uses "Advanced functions" which allows us to specify a BEGIN, PROCESS and END blocks. We use this to read a stream sent through a pipe and in the END block we process all input as a single yaml. This is why piping the contents of Get-Content works, but not sending it as a parameter.

To illustrate, we'll use the following yaml:

hi: there
goodbye: now

Using Get-Content without -Raw:

$contents = Get-Content /tmp/test.yaml
PS /tmp> $contents                             
hi: there
goodbye: now

Let's see what we got:

PS /tmp> $contents.GetType().FullName
System.Object[]

As we can see, this is an array of objects, not a string. If we try to pass it as a positional parameter, ConvertFrom-Yaml will try to convert from string to powershell objects, so we'll get an error:

PS /tmp> ConvertFrom-Yaml $contents
ConvertFrom-Yaml: Cannot process argument transformation on parameter 'Yaml'. Cannot convert
value to type System.String.

But piping the same object, will work due to how the BEGIN, PROCESS, END workflow works:

PS /tmp> $contents | ConvertFrom-yaml          

Name                           Value
----                           -----
hi                             there
goodbye                        now

To save yourself the headache, simply use the -Raw flag when you use Get-Content:

PS /tmp> $contents = Get-Content -Raw /tmp/test.yaml
PS /tmp> $contents.GetType().FullName
System.String
PS /tmp> ConvertFrom-Yaml $contents

Name                           Value
----                           -----
hi                             there
goodbye                        now

PS /tmp> $contents | ConvertFrom-Yaml

Name                           Value
----                           -----
hi                             there
goodbye                        now

from powershell-yaml.

Also, if ordering is important, use the -Ordered flag when using ConvertFrom-Yaml.

from powershell-yaml.