Add a new asdf direnv install command

Before this diff, it was impossible to install tools that depend on
other tools. For example, here's what happens if I try to install a
version of poetry on my machine:

    $ asdf install poetry 1.5.1
    No version is set for command python3
    Consider adding one of the following versions in your config file at
    python 3.10.2
    python 3.8.10
    curl: (23) Failure writing output to destination

    Cleanup: Something went wrong!

    48 /home/jeremy/.asdf/plugins/poetry/bin/install: POETRY_HOME=$install_path python3 - --version "$version" $flags

This is because my system doesn't actually have a global `python` or
`python3`. While I *could* install python with my system's package
manager, I'd rather re-use my asdf-managed python if at all possible.
Plus, poetry's installer doesn't even work with the 2 most popular ways
of installing python systemwide on macOS (see [this poetry
issue](python-poetry/install.python-poetry.org#24 (comment))
and [this homebrew issue](Homebrew/homebrew-core#138159)).

I know this doesn't solve the general build-dependencies issue: asdf is
not a full package manager and I doubt it ever will become one. I do
think this fairly minor change is worth implementing though, as it will
solve a pain point my team has started running into ever since [homebrew
changed they way they build binaries and that broke poetry
install](Homebrew/homebrew-core#138159).

As a happy side effect, we can now run `direnv reload` for the user,
which saves them a command whenever they need to install missing
dependencies.

CHANGELOG.md

@@ -11,11 +11,16 @@ github compare-link with the previous one.
 
 ## [Unreleased](https://github.com/asdf-community/asdf-direnv/compare/v0.3.0..master)
 
+- Add new `asdf direnv install` command to help when installing tools that depend on each other. #180
+
 - Fix `find` warning. #178
+
 - Add '--no-touch-rc-file' option to prevent rc file modification during updates. #176
+
 - Alternatively, `export ASDF_DIRENV_NO_TOUCH_RC_FILE=1` to prevent rc file modification. #176
 
 - Add support for resolving 'latest:X' in .tool-versions #136
+
 - Add support for resolving 'latest' in .tool-versions #168
 
 ## [0.3.0](https://github.com/asdf-community/asdf-direnv/compare/v0.3.0) (2022-04-03)

lib/commands/command-install.bash

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+# Exit on error, since this is an executable and not a sourced file.
+set -Eeuo pipefail
+
+# shellcheck source=lib/install-lib.bash
+source "$(dirname "${BASH_SOURCE[0]}")/../install-lib.bash"
+install_command "$@"

lib/install-lib.bash

@@ -0,0 +1,97 @@
+#!/usr/bin/env bash
+
+# shellcheck source=lib/tools-environment-lib.bash
+source "$(dirname "${BASH_SOURCE[0]}")/tools-environment-lib.bash"
+
+function print_usage() {
+  echo "Usage: asdf direnv install"
+  echo ""
+  echo "Installs tools needed for the current directory. This is very similar"
+  echo "to 'asdf install' except it installs the tools in the exact order specified"
+  echo "in the '.tool-versions' file, and loads the environment of each tool in order."
+  echo ""
+  echo "This is useful when installing tools that depend on other tools, for"
+  echo "example: the poetry plugin expects python to be available."
+  echo ""
+  echo "Note: this problem isn't entirely unique to asdf-direnv. asdf itself"
+  echo "isn't a full-fledged package manager. It simply doesn't understand"
+  echo "dependencies between plugins and therefore cannot do a dependency sort of"
+  echo "tools. You'll need to manually sort the lines of your '.tool-versions' file"
+  echo "for this to work as intended. See these discussions in core asdf for"
+  echo "more information:"
+  echo ""
+  echo " - https://github.com/asdf-vm/asdf/issues/929"
+  echo " - https://github.com/asdf-vm/asdf/issues/1127"
+  echo " - https://github.com/asdf-vm/asdf/issues/196"
+}
+
+function install_command() {
+  while [[ $# -gt 0 ]]; do
+    arg=$1
+    shift
+    case $arg in
+      -h | --help)
+        print_usage
+        exit 1
+        ;;
+      *)
+        echo "Unknown option: $arg"
+        exit 1
+        ;;
+    esac
+  done
+
+  install_tools
+}
+
+_load_asdf_functions_installs() {
+  # `install_tool_version` depends on `reshim_command` from reshim.bash.
+  # See https://github.com/asdf-vm/asdf/blob/v0.12.0/lib/functions/installs.bash#L243
+  _load_asdf_lib reshim_command commands/reshim.bash
+
+  _load_asdf_lib install_tool_version functions/installs.bash
+}
+
+function maybe_install_tool_version() {
+  _load_asdf_functions_installs
+
+  local install_path
+  install_path=$(get_install_path "$plugin_name" "version" "$version")
+
+  if [ -d "$install_path" ]; then
+    printf "%s %s is already installed\n" "$plugin_name" "$version"
+  else
+
+    # NOTE: we temporarily loosen the rules while invoking
+    # install_tool_version because it's from core asdf and it doesn't run
+    # well under "strict mode" (asdf_run_hook invokes get_asdf_config_value
+    # in a way such that if the config piece is missing, the program exits
+    # immediately if `set -e` is enabled.
+    (
+      set +ue
+      install_tool_version "$plugin_name" "$version"
+      set -ue
+    )
+  fi
+}
+
+function install_tools {
+  local tools_file
+  tools_file="$(_local_versions_file)"
+
+  while IFS=$'\n' read -r plugin_name; do
+    while IFS=$'\n' read -r version_and_path; do
+      local version _path
+      IFS='|' read -r version _path <<<"$version_and_path"
+
+      # Install this tool version if not already installed.
+      maybe_install_tool_version "$plugin_name" "$version"
+
+      # Load the tools environment so subsequent installs can use this tool.
+      direnv_code=$(_plugin_env_bash "$plugin_name" "$version" ">>> UH OH <<<")
+      eval "$direnv_code"
+    done <<<"$(_plugin_versions_and_path "$plugin_name")"
+  done <<<"$(_plugins_in_file "$tools_file")"
+
+  direnv reload
+}

lib/tools-environment-lib.bash

@@ -213,22 +213,23 @@ _load_local_plugins_env() {
   fi
 }
 
-# from asdf plugin_current_command
-_load_plugin_version_and_file() {
+function _plugin_versions_and_path() {
   local plugin_name=$1
   local versions_and_path
-  # NOTE: temporary disable nounset since find_versions expects ASDF_DEFAULT_TOOL_VERSIONS_FILENAME to be set.
+  # NOTE: temporarily disable nounset since find_versions expects
+  # ASDF_DEFAULT_TOOL_VERSIONS_FILENAME to be set.
   versions_and_path="$(
     set +u
     find_versions "$plugin_name" "$(pwd)"
     set -u
   )"
-  if test -z "$versions_and_path"; then
+  if [ -z "$versions_and_path" ]; then
     return 0
   fi
 
   local path
   path=$(cut -d '|' -f 2 <<<"$versions_and_path")
+
   local versions=()
   while IFS=$' \t' read -r -a inline_versions; do
     for ((idx = ${#inline_versions[@]} - 1; idx >= 0; idx--)); do
@@ -237,12 +238,30 @@ _load_plugin_version_and_file() {
   done <<<"$(cut -d '|' -f 1 <<<"$versions_and_path" | uniq | _tail_r)"
 
   for version in "${versions[@]}"; do
-    echo log_status "using asdf ${plugin_name} ${version}"
-    _plugin_env_bash "$plugin_name" "$version" "$plugin_name $version not installed. Run 'asdf install' and then 'direnv reload'."
+    printf '%q|%q\n' "$version" "$path"
   done
-  if [ -f "$path" ]; then
-    printf 'watch_file %q\n' "$path"
+}
+
+# from asdf plugin_current_command
+_load_plugin_version_and_file() {
+  local plugin_name=$1
+
+  local plugin_versions_and_path
+  plugin_versions_and_path="$(_plugin_versions_and_path "$plugin_name")"
+  if [ -z "$plugin_versions_and_path" ]; then
+    return 0
   fi
+
+  while IFS=$'\n' read -r version_and_path; do
+    local version path
+    IFS='|' read -r version path <<<"$version_and_path"
+
+    echo log_status "using asdf ${plugin_name} ${version}"
+    _plugin_env_bash "$plugin_name" "$version" "$plugin_name $version not installed. Run 'asdf direnv install' to install."
+    if [ -f "$path" ]; then
+      printf 'watch_file %q\n' "$path"
+    fi
+  done <<<"$plugin_versions_and_path"
 }
 
 _new_items() {