Follow HTML standards for query string List

[vincentsarago]

Discussed in #349

^{Originally posted by vincentsarago July 28, 2021}
ref: #347, #262 (comment)

Problem description

Historically we choose to allow passing list values (bidx, bands, assets) as comma delimited value encoded in string (e.g bidx=1,2,3), which is then decoded to list

titiler/src/titiler/core/titiler/core/dependencies.py

Lines 89 to 101 in 1879706

	class BidxParams(DefaultDependency):
	"""Band Indexes parameters."""
	bidx: Optional[str] = Query(
	None, title="Band indexes", description="comma (',') delimited band indexes",
	)
	def __post_init__(self):
	"""Post Init."""
	if self.bidx is not None:
	self.kwargs["indexes"] = tuple(
	int(s) for s in re.findall(r"\d+", self.bidx)
	)

This works fine BUT is not standard.

Breaking change

this will be a breaking change but I feel it's better to follow standard.

[vincentsarago]

In next titiler version (0.4) we will update all the dependencies to follow HTML standards

When list is required, the use will have to pass the argument multiple times: indexes=1&indexes=2&indexes=3 (before it was bidx=1,2,3

Open Question

In new rio-tiler (3.0) we need asset_expression and asset_indexes to be dictionaries (e.g asset_expression={"asset1": "b1*2"} . Sadly there is no standard ways to represent dictionaries/object in query strings, and starlette don't support it.

I'm quite fond of the mydict[mykey]=value notation (e.g asset_expression[asset1]=b1*2)

Note: seems that the notation refers to deepObject in OpenAPI3.0.1

ref:

• https://spec.openapis.org/oas/v3.1.0#style-values
• https://blog.shalvah.me/posts/fun-stuff-representing-arrays-and-objects-in-query-strings