fix(gh-r): detect musl from its loader, not from curl (#576)

.github/workflows/zsh-n.yml

@@ -26,6 +26,7 @@ on:
       - "tests/archive-extraction.zsh"
       - "tests/completion-refresh.zsh"
       - "tests/disk-ice-resolution.zsh"
+      - "tests/gh-r-musl-detection.zsh"
       - "tests/home-preparation.zsh"
       - "tests/hook-ownership.zsh"
       - "tests/ice-tokenizer.zsh"
@@ -278,6 +279,17 @@ jobs:
       - name: Test disk ice resolution
         run: zsh -f tests/disk-ice-resolution.zsh
 
+  gh-r-musl-detection:
+    name: gh-r musl detection
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install Zsh
+        run: sudo apt update && sudo apt-get install -yq zsh
+      - name: Test gh-r musl detection
+        run: zsh -f tests/gh-r-musl-detection.zsh
+
   parallel-update:
     name: Parallel Update
     runs-on: ubuntu-latest

lib/zsh/install.zsh

@@ -1626,6 +1626,15 @@ builtin source "${ZI[BIN_DIR]}/lib/zsh/side.zsh" || { builtin print -P "${ZI[col
 }
 # ]]]
 
+# FUNCTION: .zi-has-musl-loader [[[
+# Succeeds when DIR ($1) holds a musl dynamic loader (ld-musl-<arch>.so.1).
+.zi-has-musl-loader() {
+  builtin emulate -LR zsh
+  local -a loaders=( $1/ld-musl-*(N) )
+  (( $#loaders ))
+}
+# ]]]
+
 # FUNCTION: .zi-get-latest-gh-r-url-part [[[
 # Gets version string of latest release of given Github package.
 # Connects to Github releases page.
@@ -1650,9 +1659,11 @@ builtin source "${ZI[BIN_DIR]}/lib/zsh/side.zsh" || { builtin print -P "${ZI[col
     local url=https://$urlpart
   fi
 
-  if (( ${+commands[curl]} )) || find /lib/ -maxdepth 1 -name '*musl*' >/dev/null 2>&1; then
-    HAS_MUSL='linux-musl'
-  fi
+  # A musl host ships its dynamic loader in /lib as ld-musl-<arch>.so.1.
+  # Match that file: find exits 0 with no match, a broader *musl* also
+  # matches a musl toolchain directory on a glibc host, and whether curl
+  # is installed says nothing about the C library.
+  .zi-has-musl-loader /lib && HAS_MUSL='linux-musl'
 
   local -A matchstr
   matchstr=(

tests/gh-r-musl-detection.zsh

@@ -0,0 +1,95 @@
+#!/usr/bin/env zsh
+# -*- mode: zsh; sh-indentation: 2; indent-tabs-mode: nil; sh-basic-offset: 2; -*-
+# vim: ft=zsh sw=2 ts=2 et
+# Verify gh-r musl detection (z-shell/zi#576) without network access or
+# caller state: it looks for the musl loader, and does not depend on
+# whether curl is installed.
+builtin emulate -R zsh
+setopt pipe_fail
+
+typeset project_root=${0:A:h:h}
+typeset temp_root=$(command mktemp -d "${TMPDIR:-/tmp}/zi-gh-r-musl.XXXXXXXX") || exit 1
+trap 'command rm -rf -- "$temp_root"' EXIT INT TERM
+export HOME=$temp_root/home ZDOTDIR=$temp_root/home TMPDIR=$temp_root/tmp
+command mkdir -p -- "$HOME" "$TMPDIR" || exit 1
+typeset -gA ZI=( HOME_DIR $temp_root/data CACHE_DIR $temp_root/cache CONFIG_DIR $temp_root/config )
+typeset -gx ZPFX=$temp_root/prefix
+source "$project_root/zi.zsh" || exit 1
+builtin source "$project_root/lib/zsh/install.zsh" >/dev/null || { print -u2 -r -- 'not ok - source install library'; exit 1; }
+
+# Detection: a directory with the loader is musl; a musl toolchain
+# directory or an empty directory is not.
+typeset lib_musl=$temp_root/lib-musl lib_toolchain=$temp_root/lib-toolchain lib_empty=$temp_root/lib-empty
+command mkdir -p -- "$lib_musl" "$lib_toolchain/musl" "$lib_empty" || exit 1
+: > "$lib_musl/ld-musl-${CPUTYPE:-x86_64}.so.1" || exit 1
+.zi-has-musl-loader "$lib_musl" || { print -u2 -r -- 'not ok - a musl loader was not detected'; exit 1; }
+if .zi-has-musl-loader "$lib_toolchain"; then
+  print -u2 -r -- 'not ok - a musl toolchain directory was taken for a musl host'
+  exit 1
+fi
+if .zi-has-musl-loader "$lib_empty"; then
+  print -u2 -r -- 'not ok - an empty directory was taken for a musl host'
+  exit 1
+fi
+
+# A release that publishes both a glibc and a musl build for this machine.
+typeset gnu_asset=/owner/tool/releases/download/v1/tool-${CPUTYPE:-x86_64}-unknown-linux-gnu.tar.gz
+typeset musl_asset=/owner/tool/releases/download/v1/tool-${CPUTYPE:-x86_64}-unknown-linux-musl.tar.gz
+.zi-download-file-stdout() {
+  print -r -- "<a href=\"$gnu_asset\">gnu</a>"
+  print -r -- "<a href=\"$musl_asset\">musl</a>"
+}
+typeset -gA ICE=( ver v1 )
+
+# pick_with_curl 0|1 [musl]: the asset chosen with curl absent or present.
+# The function runs grep and uname, so each case gets a PATH holding only
+# those, plus a curl for the second case. With "musl", the host is taken
+# to have a musl loader.
+pick_with_curl() {
+  local bin=$temp_root/bin$1 tool
+  command mkdir -p -- "$bin" || return 1
+  for tool in grep uname; do
+    command ln -sf -- "${commands[$tool]:?$tool not found}" "$bin/$tool" || return 1
+  done
+  if (( $1 )); then
+    print -r -- '#!/bin/sh' > "$bin/curl" && command chmod +x -- "$bin/curl" || return 1
+  fi
+  (
+    [[ $2 == musl ]] && .zi-has-musl-loader() { return 0; }
+    path=( $bin )
+    builtin hash -r
+    reply=()
+    .zi-get-latest-gh-r-url-part owner tool >/dev/null 2>&1 || exit 1
+    print -r -- $reply[1]
+  )
+}
+
+typeset without_curl with_curl
+without_curl=$(pick_with_curl 0) || { print -u2 -r -- 'not ok - no asset chosen without curl'; exit 1; }
+with_curl=$(pick_with_curl 1) || { print -u2 -r -- 'not ok - no asset chosen with curl'; exit 1; }
+
+[[ $with_curl == $without_curl ]] || {
+  print -u2 -r -- "not ok - installing curl changed the chosen asset: $without_curl -> $with_curl"
+  exit 1
+}
+
+# On a Linux host without a musl loader, the musl preference must not
+# apply, so the musl build is not chosen over the glibc build listed
+# first. Which of two matching builds wins otherwise is the asset order;
+# this test does not claim that glibc is actively preferred.
+if [[ $OSTYPE == linux* ]] && ! .zi-has-musl-loader /lib; then
+  [[ $with_curl == $gnu_asset ]] || {
+    print -u2 -r -- "not ok - a host without a musl loader chose $with_curl instead of $gnu_asset"
+    exit 1
+  }
+fi
+
+# On a musl host the musl build wins even when the glibc build is listed
+# first, so the detection result reaches the asset filter.
+typeset on_musl
+on_musl=$(pick_with_curl 0 musl) || { print -u2 -r -- 'not ok - no asset chosen on a musl host'; exit 1; }
+[[ $on_musl == $musl_asset ]] || {
+  print -u2 -r -- "not ok - a musl host chose $on_musl instead of $musl_asset"
+  exit 1
+}
+print -r -- 'ok - gh-r musl detection looks for the loader and ignores curl'