feat(zsh): allow configuring settings like HOME_DIR/BIN_DIR via zstyle

Resolve ZINIT[...] settings from `zstyle ':zinit:config' <attr>` before
the BIN_DIR/HOME_DIR/derived-dir logic runs. The attribute name is the
hash field lowercased with `_` replaced by `-` (HOME_DIR -> home-dir).

An explicitly-set ZINIT[KEY] always wins over zstyle, which wins over
the built-in default; fully backward-compatible.

Signed-off-by: Vladislav Doster <mvdoster@gmail.com>

.github/workflows/tests.yaml

@@ -33,6 +33,7 @@ jobs:
           - annexes
           - commands
           - compile
+          - config-zstyle
           - gh-r
           - ices
           - plugins

README.md

@@ -1150,6 +1150,22 @@ ### Customizing Paths<a name="customizing-paths"></a>
 There is also `$ZPFX`, set by default to `~/.local/share/zinit/polaris` – a directory where software with `Makefile`,
 etc. can be pointed to, by e.g. `atclone'./configure --prefix=$ZPFX'`.
 
+#### Configuring via `zstyle`
+
+As an alternative to pre-setting the `$ZINIT` hash, the same settings can be configured with `zstyle` under the
+`:zinit:config` context. The attribute name is the hash field lowercased with `_` replaced by `-` (e.g.
+`ZINIT[HOME_DIR]` ⇄ `zstyle ':zinit:config' home-dir`). This works for every field in the table above, as well as
+`services-dir`, `module-dir`, `polaris-dir` and `zpfx`.
+
+Precedence is: an explicitly-set `ZINIT[KEY]` wins over a `zstyle`, which in turn wins over the built-in default. So the
+`zstyle` only fills fields you did not set in the hash, keeping the setup fully backward-compatible.
+
+```zsh
+zstyle ':zinit:config' home-dir      ~/.zinit
+zstyle ':zinit:config' bin-dir       ~/.zinit/zinit.git
+zstyle ':zinit:config' mute-warnings 1
+```
+
 ### Non-GitHub (Local) Plugins<a name="non-github-local-plugins"></a>
 
 Use `create` subcommand with user name `_local` (the default) to create plugin's skeleton in `$ZINIT[PLUGINS_DIR]`. It

tests/config-zstyle.zunit

@@ -0,0 +1,68 @@
+#!/usr/bin/env zunit
+# vim:ft=zsh:sw=4:sts=4:et:foldmarker={,}:foldmethod=marker
+#
+# zdharma-continuum/zinit/tests/config-zstyle.zunit
+# Copyright (c) 2016-2021 Sebastian Gniazdowski
+# Copyright (c) 2021-2024 zdharma-continuum
+# Homepage: https://github.com/zdharma-continuum/zinit
+# License: MIT License
+#
+# Tests for configuring ZINIT[...] settings via `zstyle ':zinit:config' ...'.
+#
+# NOTE: the test bootstrap pre-sets every ZINIT[KEY], which would mask the
+# zstyle path. Each test therefore exercises the feature in a CLEAN
+# `zsh -fc` subshell that sets a zstyle, sources the patched zinit.zsh
+# (located at ${ZINIT[BIN_DIR]}/zinit.zsh inside the test env) and prints the
+# resulting hash field.
+#
+# The subshell is captured with `$(...)` rather than zunit's `run`: `run`
+# re-`eval`s its arguments in the *outer* process, where the bootstrap has
+# already populated ZINIT[HOME_DIR] et al., which would clobber the inner
+# `${ZINIT[...]}` reads we want to observe. Single-quoting the inner script
+# defers those reads to the subshell; only ${ZINIT[BIN_DIR]} is expanded
+# (concatenated in) by the outer shell to locate zinit.zsh.
+#
+
+@test 'zstyle fills an unset key' {
+    output=$(zsh -fc 'zmodload zsh/zutil; typeset -gAH ZINIT
+        ZINIT[BIN_DIR]='"${ZINIT[BIN_DIR]}"'
+        zstyle ":zinit:config" home-dir /tmp/zi-fromstyle
+        source '"${ZINIT[BIN_DIR]}"'/zinit.zsh >/dev/null 2>&1
+        print -r -- ${ZINIT[HOME_DIR]}')
+    state=$?
+    assert $state equals 0
+    assert $output same_as '/tmp/zi-fromstyle'
+}
+
+@test 'explicit ZINIT[KEY] beats zstyle' {
+    output=$(zsh -fc 'zmodload zsh/zutil; typeset -gAH ZINIT
+        ZINIT[BIN_DIR]='"${ZINIT[BIN_DIR]}"'
+        ZINIT[HOME_DIR]=/tmp/zi-explicit
+        zstyle ":zinit:config" home-dir /tmp/zi-fromstyle
+        source '"${ZINIT[BIN_DIR]}"'/zinit.zsh >/dev/null 2>&1
+        print -r -- ${ZINIT[HOME_DIR]}')
+    state=$?
+    assert $state equals 0
+    assert $output same_as '/tmp/zi-explicit'
+}
+
+@test 'derived dir follows zstyle-provided home-dir' {
+    output=$(zsh -fc 'zmodload zsh/zutil; typeset -gAH ZINIT
+        ZINIT[BIN_DIR]='"${ZINIT[BIN_DIR]}"'
+        zstyle ":zinit:config" home-dir /tmp/zi-fromstyle
+        source '"${ZINIT[BIN_DIR]}"'/zinit.zsh >/dev/null 2>&1
+        print -r -- ${ZINIT[PLUGINS_DIR]}')
+    state=$?
+    assert $state equals 0
+    assert $output same_as '/tmp/zi-fromstyle/plugins'
+}
+
+@test 'no zstyle, no array still resolves a default home-dir' {
+    output=$(zsh -fc 'zmodload zsh/zutil; typeset -gAH ZINIT
+        ZINIT[BIN_DIR]='"${ZINIT[BIN_DIR]}"'
+        source '"${ZINIT[BIN_DIR]}"'/zinit.zsh >/dev/null 2>&1
+        [[ -n ${ZINIT[HOME_DIR]} ]] && print OK')
+    state=$?
+    assert $state equals 0
+    assert $output same_as 'OK'
+}

zinit.zsh

@@ -22,6 +22,34 @@ typeset -gAH ZPLGM
 ZINIT=( "${(kv)ZPLGM[@]}" "${(kv)ZINIT[@]}" )
 unset ZPLGM
 
+#
+# Allow configuring ZINIT[...] settings via zstyle, e.g.:
+#   zstyle ':zinit:config' home-dir ~/.zinit
+#   zstyle ':zinit:config' bin-dir  ~/.zinit/zinit.git
+# An explicitly-set ZINIT[KEY] always wins over the matching zstyle.
+#
+if zmodload -F zsh/zutil +b:zstyle 2>/dev/null || (( ${+builtins[zstyle]} )); then
+    () {
+        local _attr _key
+        local -A _map=(
+            bin-dir         BIN_DIR          home-dir         HOME_DIR
+            plugins-dir     PLUGINS_DIR      completions-dir  COMPLETIONS_DIR
+            snippets-dir    SNIPPETS_DIR     services-dir     SERVICES_DIR
+            module-dir      MODULE_DIR       polaris-dir      POLARIS_DIR
+            zpfx            ZPFX             man-dir          MAN_DIR
+            list-command    LIST_COMMAND     zcompdump-path   ZCOMPDUMP_PATH
+            compinit-opts   COMPINIT_OPTS    mute-warnings    MUTE_WARNINGS
+            no-aliases      NO_ALIASES       packages-branch  PACKAGES_BRANCH
+            packages-repo   PACKAGES_REPO
+            optimize-out-disk-accesses OPTIMIZE_OUT_DISK_ACCESSES
+        )
+        for _attr _key in "${(kv)_map[@]}"; do
+            [[ -n ${ZINIT[$_key]} ]] && continue
+            zstyle -s ':zinit:config' "$_attr" "ZINIT[$_key]"
+        done
+    }
+fi
+
 #
 # Common needed values.
 #