How to expose sub module function, from a module - powershell

Question

How do you expose a function and an alias from a module, from a sub module
profile.ps1:
Import-Module module_one.psm1
module_one.psm1:
Import-Module module_two.psm1:
module_two.psm1:
Set-Alias readme -Value "Read-Me"
function Read-Me() {
Write-Host "Hello..."
}
Export-ModuleMember -Function Read-Me, readme
I want to be able to call this function from the pwsh terminal, function name or alias?
I get (readme or Read-Me):
Read-Me : The term 'Read-Me' is not recognized as the name of a cmdlet,
function, script file, or operable program. Check the spelling of the name,
or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ co
+ ~~
+ CategoryInfo : ObjectNotFound: (co:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
Note: it works for functions in module_one.psm1.

Answer 1

Assuming that you call Import-Module module_one.psm1 and later readme / Read-Me in the same scope domain (either outside a module or from the same (other) module), your code works in principle:
The exported elements of the indirectly imported module are (also) imported into the top scope of the caller's scope domain.
Your problem is that you're trying to export alias readme as a function; you need to use the separate -Alias parameter instead:
Export-ModuleMember -Function Read-Me -Alias readme # Note the -Alias parameter
Also note that in the absence of an Export-ModuleMember call it is all (top-level) functions and aliases (but not variables) that are exported by default, so in your particular case simply omitting the call would have fixed the problem too.
In general, though, it is better to be explicit about what elements are exported, and that is best done via a full-fledged module that is not just a single *.psm1 file, but an entire directory named for the module, housing the *.psm1 file with an associated module manifest, which is a *.psd1 file that describes the module, notably also in terms of its exports.
If such a module is placed in one of the directories listed in $env:PSModulePath, its exported commands can be discovered (e.g., with Get-Command or tab-completion) even before the module is imported, via a feature called auto-loading - see about_Modules.
Note that Import-Module -Global is rarely needed and should generally be avoided, because it makes a module's exported elements available to all loaded modules too, which can have unintended side effects (modules should declare their dependencies explicitly).