Can't install new Homebrew formula

(Homebrew version 3.6.21)

I'm trying to create and install a new formula, but when I try to install it Homebrew first tries to fetch the formula from Github, which of course fails because it's only on my local machine at the moment.

I'm trying to roll back to an old version of some software, so the new formula is named name@x.y.z. I initially tried editing the existing formula with brew edit, but found that Homebrew kept using the URLs for the newer version, even though I'd edited the formula - probably because it was fetching the formula from Github and using that instead of using my edited version.

Steps to reproduce:

• brew create --set-name <formula-name> <some-url>
• Edit the formula
• brew install -s <formula-name>

Result:

==> Fetching <formula-name>
curl: (22) The requested URL returned error: 404

Error: Failure while executing; `/usr/bin/env /opt/homebrew/Library/Homebrew/shims/shared/curl \
	--disable \
	--cookie /dev/null \
	--globoff \
	--show-error \
	--user-agent Homebrew/3.6.21-164-ge42cae1\ \(Macintosh\;\ arm64\ Mac\ OS\ X\ 13.2\)\ curl/7.86.0 \
	--header Accept-Language:\ en \
	--fail \
	--progress-bar \
	--retry 3 \
	--location \
	--remote-time \
	--output /Users/alastaid/Library/Caches/Homebrew/Formula/<formula-name>.rb \
	https://raw.githubusercontent.com/Homebrew/homebrew-core/9a6a815e5ea0169b46e10f411ac3237740a6bbdf/Formula/<formula-name>.rb`
exited with 22. Here&#39;s the output:
curl: (22) The requested URL returned error: 404

How can I force Homebrew to use my edited / created formula instead of downloading from GitHub?

And if I edit a formula in the future, how do I prevent Homebrew from trying to re-download the formula I'm trying to test and overwriting my changes?

I believe this problem is due to the documentation not having been updated yet for homebrew v4.0. I can reproduce the problem based on your instructions, and here is my brew --version:

brew --version
Homebrew 4.0.3
Homebrew/homebrew-core (git revision 63589f1a8e3; last commit 2023-02-16)
Homebrew/homebrew-cask (git revision ce33115a81; last commit 2023-02-16)

It looks like there is a PR to update the documentation for v4.0, which says the following:

> As you are developing, you'll also need to set HOMEBREW_NO_INSTALL_FROM_API=1 before any install commands, to force brew to use the local repository instead of the API.

So instead of your previous brew install command, run this:

HOMEBREW_NO_INSTALL_FROM_API=1 brew install --build-from-source <formula-name>

I tried this and it got me past the failing download. You will probably still need to edit your formula to make sure it works correctly.