livecheck currently doesn't support `POST` requests but it wasn't
entirely clear how best to handle that. I initially approached it as
a `Post` strategy but unfortunately that would have required us to
handle response body parsing (e.g., JSON, XML, etc.) in some fashion.
We could borrow some of the logic from related strategies but we would
still be stuck having to update `Post` whenever we add a strategy for
a new format.
Instead, this implements `POST` support by borrowing ideas from the
`using: :post` and `data` `url` options found in formulae. This uses
a `post_form` option to handle form data and `post_json` to handle
JSON data, encoding the hash argument for each into the appropriate
format. The presence of either option means that curl will use a
`POST` request.
With this approach, we can make a `POST` request using any strategy
that calls `Strategy::page_headers` or `::page_content` (directly or
indirectly) and everything else works the same as usual. The only
change needed in related strategies was to pass the options through
to the `Strategy` methods.
For example, if we need to parse a JSON response from a `POST`
request, we add a `post_data` or `post_json` hash to the `livecheck`
block `url` and use `strategy :json` with a `strategy` block. This
leans on existing patterns that we're already familiar with and
shouldn't require any notable maintenance burden when adding new
strategies, so it seems like a better approach than a `Post` strategy.
This refactors verbose code in the `Sparkle` strategy where we access
element text into a reusable `Xml#element_text` method, replacing
chained calls like `item.elements["title"]&.text&.strip&.presence`
with `Xml.element_text(item, "title")`.
`#element_text` is only used to retrieve the text of a child element
in the `Sparkle` strategy but it can also retrieve the text from the
provided element if the `child_path` argument is omitted (i.e.,
`Xml.element_text(item)`). This will allow us to also avoid similar
calls like `item.text.strip.presence` in the future.
Since we use `REXML::Document` in the type signature for `#parse_xml`,
we can encounter an `uninitialized constant
Homebrew::Livecheck::Strategy::Xml::REXML` error in strategies like
`Sparkle` that use `Xml#parse_xml` internally when the Sorbet runtime
is used. Moving the related require outside of the `#parse_xml` method
and into the `Xml` strategy proper resolves this issue.
This adds a generic `Xml` strategy to livecheck that requires a
`strategy` block to operate. The XML-parsing code is taken from the
existing approach in the `Sparkle` strategy. As such, `Sparkle` has
been updated to use the `Xml#parse_xml` method instead.
Unlike the `Json` strategy, we don't currently have any `strategy`
blocks in first-party taps that manually parse XML. However, we had a
user request support for something like this and I was already working
on an `Xml` strategy (as a way of extracting the XML-parsing code
from `Sparkle` into something general-purpose), so here we are.
Future strategies that parse simple XML data can potentially use the
`Xml#find_versions` method (similar to how we have strategies that
leverage `PageMatch#find_versions`) instead of having to implement
something bespoke like `Sparkle`.
