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your original object doesn't have a addons key, hence you can't call the push property on it, first create that key and assign to empty array

Although they 'don't exist', can Format.ps1xml files be created/used in versions of PowerShell greater than 5.1?

• Yes; in fact any third-party code must use them to define custom formatting.

  • That *.ps1xml files are invariably needed for such definitions is unfortunate; GitHub issue #7845 asks for an in-memory, API-based alternative (which for type data already exists, via the Update-TypeData cmdlet).

• It is only the formatting data that ships with PowerShell that is now hardcoded into the PowerShell (Core) executable, presumably for performance reasons.

is there some better practice for suggesting to PowerShell how a certain function should format returned data?

The lack of an API-based way to define formatting data requires the following approach:

• Determine the full name of the .NET type(s) to which the formatting should apply.

  • If it is [pscustomobject] instances that the formatting should apply to, you need to (a) choose a unique (virtual) type name and (b) assign it to the [pscustomobject] instances via PowerShell's ETS (Extended Type System); e.g.:

    • For [pscustomobject] instances created by the Select-Object cmdlet:

Use JOIN, FULL JOIN in fact:

Short answer: You can't.

It was possible in MongoDB version <= 3.6 where there was an option to bypass the validation completely using the check_keys=False option. But this option is deprecated ever since.

Although MongoDB has bypass_document_validation=True in newer versions, it won't bypass the . character for obvious reasons.

There is an open issue regarding this on JIRA (SERVER-30575) and it is still open. Also, the PyMongo specific issue related to this was raised once PYTHON-1522.

So until the SERVER-30575 issue fixed, you have no other choice.

I would suggest you rearrange your schema design to embed the key name as a value to a different key.

Something like this:

This issue is raised and still open (4 years!) on the WinAppDriver repo.

Here's the workaround that a user suggested there.

I updated the code like this:

Have a go with this

We need /u to handle unicode and then .+ instead of \w because of the double bytes

More stuff using Unicode regex

Regular expression \p{L} and \p{N}

You must make a distinction between the static type of a variable (the type known at compile time) and the run time type of an object reference assigned to a variable.

The static type of p is Parent in both cases because it is declared as Parent p. No matter what you assign it. You may even assign it null.

The run time type of the value of p after the assignment is Child in the first case and Parent in the second case. It would be undetermined if p was null.

It is okay to assign a Child to a Parent, because the Child class derives from Parent. A Child is therefore a Parent (in OO terms).

However, a Parent is not a Child, because it does not derive from it. Therefore, in the second case, you cannot cast p to Child. In the first case the cast is valid, because you cast the object to its actual run time type. It tells the compiler, I know that this object assigned to a Parent variable is a Child, so, please, treat it as a Child. This does not involve any conversion; however, a runtime check will be performed, possibly throwing an exception, if the cast was not allowed.

You were asked to explain it from point of view of stack and heap memory. I'm sorry to say, but this has absolutely nothing to do with stack or heap memory. It has to do with inheritance rules and assignment compatibility.

Of course, here we are dealing with reference types (classes). This allows us to derive Child from Parent. This would not be possible with value types (structs). The point is reference type versus value type, not heap versus stack, which is an implementation detail. And btw., a value type (struct) field in a class will also be stored on the heap.

See also: The Stack Is An Implementation Detail, Part One and Two (Eric Lippert's blog)

You did not ask for it but casting to a derived type is mostly preceded by a type test, because you usually do not know the run time type in advance. Let us say that the Child class adds a new method DriveParentsToDespair() (only children can do this). Then you could use Type testing with pattern matching to test the type and assign it to a new variable at the same time:

You can use -