[core-rest-pipeline] Fix serialization of body of false

[deyaaeldeen]

If the body contains just false, this check will confuse it with the body being non existent. This PR fixes this issue.

[jeremymeng]

Looks like this is ported from

azure-sdk-for-js/sdk/core/core-http/src/serviceClient.ts

Line 581 in f1dc4f7

if ((httpRequest.body !== undefined && httpRequest.body !== null) || required) {

. We could add the null case too just to be safe?

[jeremymeng]

Or is there a case that we actually want to use null request body

[deyaaeldeen]

@jeremymeng I do not think body can be null, according to its type at least.

[bterlson]

Little bit worried about null bodies since its a valid JSON value. Supporting all JSON values in body seems like a good idea to me.

[jeremymeng]

@jeremymeng I do not think body can be null, according to its type at least.

@deyaaeldeen the union type has null, unless I am missing anything. I don't see boolean in it, a different issue though

azure-sdk-for-js/sdk/core/core-rest-pipeline/src/interfaces.ts

Line 57 in f1dc4f7

| null;

[deyaaeldeen]

@jeremymeng You are right, I missed it. Updated accordingly.

[deyaaeldeen]

@bterlson good point! I think it makes sense to revert 88abff3. @jeremymeng thoughts?

[jeremymeng]

I was looking at the truth table in serialize() and the condition we throw errors. It feels to me that we may also want to check nullable to ensure we don't pass null to serialize() if it is not the nullable case? thoughts?
https://github.com/Azure/azure-sdk-for-js/blob/master/sdk/core/core-client/src/serializer.ts#L150

[jeremymeng]

What I meant is

-    if ((request.body !== undefined && request.body !== null) || required) {
+    if ((request.body !== undefined && request.body !== null) || (nullable && request.body === null) || required) {

but it is an additional case to allow null so current PR should be good.

[ghost]

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