Why is this ZSH function not setting the variables, and outputting a git command instead?

Trying to create a custom git function to check to see how far ahead/behind a branch is to another branch. The logic works, if I copy/paste line by line in a terminal it works.

However, putting this in my .zshrc does not:

function gba() {
  branch="$(git rev-parse --abbrev-ref HEAD)"
  counts_str="$(git rev-list --left-right --count origin/dev...$branch)"
  counts=(${(ps:\t:)${counts_str}})
  behind=$counts[1]
  ahead=$counts[2]

  echo "$branch behind $behind commits, ahead $ahead commits"
}

Also, if I run in in a script, adding #!/bin/zsh and executing with zsh gba.sh it works.

When I have it in my .zshrc (and make sure I open a new terminal window) it outputs all the git remote branches.

Any ideas? I'd like to have it in my .zshrc so I don't have a separate script file, and would like to run it with just gba or similar like an alias.

Findings

Based on suggestions, I've run a few things to see how gba is interpreted when defined directly in my .zshrc:

15:33:41 ~$ which gba
gba: aliased to git branch -a
15:33:46 ~$ declare -f gba
gba () {
  branch="$(git rev-parse --abbrev-ref HEAD)"
  counts_str="$(git rev-list --left-right --count origin/dev...$branch)"
  counts=(${(ps:\t:)${counts_str}})
  behind=$counts[1]
  ahead=$counts[2]
  echo "$branch behind $behind commits, ahead $ahead commits"
}
15:34:04 ~$ (set -x; gba)
+-zsh:3> git branch -a
fatal: Not a git repository (or any of the parent directories): .git

Solution

Turns out I didn't realize I had the git oh-my-zsh plugin enabled in .zshrc from the line:

plugins=(git)

This loads in a ton of aliases (which I was aware of, but I thought I had it disabled.) So commenting that line makes my gba function work perfectly. The oh-my-zsh git aliases are nice, but I would rather learn the full commands for things as I go, then later manually add aliases if I want to.

Solution

The issue is right here:

15:33:41 ~$ which gba
gba: aliased to git branch -a

...there's an alias also named gba, so your function isn't being invoked. Run unalias gba to remove it.

Incidentally, one big clue was the set -x output:

15:34:04 ~$ (set -x; gba)
+-zsh:3> git branch -a
fatal: Not a git repository (or any of the parent directories): .git

...since git branch -a isn't present anywhere in the function, this definition had to be coming from somewhere else.