feat(gvm): add auto-detect Go version from .go-version / go.mod

ChangeLog

@@ -7,6 +7,23 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 See [RELEASING.md](RELEASING.md) for the release process.
 
+## [1.3.0] - 2026-07-23
+
+### Added
+
+- `gvm use` / `gvm install` without a version resolve from the nearest `.go-version` or `go.mod` (`toolchain` / `go` directive), mapping language versions like `1.22` to the latest patch (#10 / moovweb/gvm#523).
+- Shared project version helpers; `gvm applymod` uses the same go.mod parsing and patch mapping.
+
+### Fixed
+
+- Directory walk for `.go-version` / `.go-pkgset` / `go.mod` no longer stops at the current directory only, and no longer mutates the caller's working directory.
+- Comment tests: write `go.mod` with single-line `printf` so `tf` does not hang on multi-line quotes; silence expected alias cleanup errors.
+- `.go-version` stays authoritative (no go.mod fallback after a parsed pin); accept plain `1.x.y` pins; bound remote tag listing via git HTTP low-speed abort.
+
+### Changed
+
+- Document empty-string contract for `_bash_pseudo_hash` (no distinct nil values).
+
 ## [1.2.1] - 2026-07-19
 
 ### Fixed

README.md

@@ -1,6 +1,6 @@
 # gvm2
 
-> **Status: stable for daily use (v1.2.0)**
+> **Status: stable for daily use (v1.3.0)**
 >
 > gvm2 is a community reboot of the Go Version Manager. Please file bugs and
 > contributions against this repository. Production use is supported for the
@@ -21,14 +21,25 @@ gvm use go1.22.12 --default
 go version
 ```
 
+In a module directory you can omit the version — gvm2 reads `.go-version` or
+`go.mod` (`toolchain` / `go` line) and maps language versions like `go 1.22` to
+the latest matching patch:
+
+```bash
+gvm install -B              # install version from go.mod / .go-version
+gvm use                     # select matching installed version
+```
+
 Common commands (nvm-style workflow):
 
 | Goal | Command |
 |------|---------|
 | List available versions | `gvm listall` |
 | Latest stable name only | `gvm listall --latest` |
 | Install a version | `gvm install go1.22.12` |
+| Install from project files | `gvm install` (or `gvm install -B`) |
 | Switch version | `gvm use go1.22.12` |
+| Switch from project files | `gvm use` |
 | List installed versions | `gvm list` |
 | Per-directory auto-switch | commit a `.go-version` (and optional `.go-pkgset`) |
 
@@ -63,7 +74,7 @@ triage groups the backlog into these priorities:
 | P0 | Shell integration (`cd`, PATH, zsh) | [#527](https://github.com/moovweb/gvm/issues/527), [#528](https://github.com/moovweb/gvm/issues/528), [#515](https://github.com/moovweb/gvm/issues/515) | Fixed in 1.1.0 |
 | P1 | Install / bootstrap | [#530](https://github.com/moovweb/gvm/issues/530), [#480](https://github.com/moovweb/gvm/issues/480) | Fixed in 1.1.0 |
 | P2 | UX / docs / ergonomics | [#517](https://github.com/moovweb/gvm/issues/517), [#516](https://github.com/moovweb/gvm/issues/516) | Fixed in 1.2.0 ([#4](https://github.com/brianrobt/gvm2/issues/4)) |
-| P3 | Features (progress bars, worktrees, auto-detect `go.mod`) | [#514](https://github.com/moovweb/gvm/issues/514), [#523](https://github.com/moovweb/gvm/issues/523) | Backlog |
+| P3 | Features (progress bars, worktrees, auto-detect `go.mod`) | [#514](https://github.com/moovweb/gvm/issues/514), [#523](https://github.com/moovweb/gvm/issues/523) | `go.mod` auto-detect in 1.3.0 ([#10](https://github.com/brianrobt/gvm2/issues/10)); progress / worktrees still backlog |
 
 Tracked here: [brianrobt/gvm2/issues](https://github.com/brianrobt/gvm2/issues).
 
@@ -72,6 +83,7 @@ Pull requests and other contributions are very much appreciated.
 ## Features
 
 * Install/Uninstall Go versions with `gvm install [tag]` where tag is "go1.22.12", "go1", "weekly.2011-11-08", or "tip"
+* Omit the version on `gvm install` / `gvm use` to resolve from `.go-version` or `go.mod`
 * List available versions with `gvm listall` (annotations + `--latest` / `--porcelain`)
 * List added/removed files in GOROOT with `gvm diff`
 * Manage GOPATHs with `gvm pkgset [create/use/delete] [name]`. Use `--local` as `name` to manage repository under local path (`/path/to/repo/.gvm_local`).

VERSION

@@ -1 +1 @@
-1.2.1
+1.3.0

scripts/ci-smoke.sh

@@ -24,6 +24,19 @@ if grep -q 'global:$GOPATH' "$GVM_DEST/gvm/environments/go1.22.12@global"; then
   echo "FAIL: go1.22.12@global has duplicated global GOPATH prefix" >&2
   exit 1
 fi
+# Auto-detect from go.mod (#10)
+moddir="$GVM_DEST/mod-detect"
+mkdir -p "$moddir/subdir"
+cat > "$moddir/go.mod" <<'EOF'
+module example.com/detect
+
+go 1.22
+EOF
+(
+  cd "$moddir/subdir"
+  gvm use
+  go version | grep -E 'go1\.22\.'
+)
 spaced="$GVM_DEST/dir with spaces"
 mkdir -p "$spaced"
 cd "$spaced"

scripts/env/applymod

@@ -2,29 +2,33 @@
 . "$GVM_ROOT/scripts/functions"
 
 function gvm_applymod(){
+	local mod_path=""
+	local hint=""
+	local version=""
 
-	mod_file=go.mod
-	if [ ! -f $mod_file ]; then
+	if ! mod_path="$(__gvm_find_file_upwards "go.mod")"; then
 		return $(display_error "can not find go.mod")
 	fi
 
-	mod_ver=$(cat go.mod | grep -E 'go [[:digit:]]+.[[:digit:]]+' | tr -d ' ' | tr -d '\n')
-    mod_name=$(cat go.mod | grep 'module ' | tr -d '\n')
-	display_message "$mod_name use go version: $mod_ver"
+	hint="$(__gvm_parse_go_mod_version "${mod_path}")" || hint=""
+	[[ -n "${hint}" ]] || return $(display_error "can not parse go version from go.mod")
 
-	if [ $(gvm list | grep $mod_ver | wc -l | tr -d '\n') -lt 1 ]; then
-		if [ $(gvm listall -a| grep $mod_ver | wc -l | tr -d '\n') -lt 1 ]; then
-			return $(display_error "can not find a go version match $mod_ver") 
-		fi
+	# Prefer an already-installed match; otherwise resolve the latest available patch.
+	version="$(__gvm_map_version_hint_to_tag "${hint}" installed)" || version=""
+	if [[ -z "${version}" ]]; then
+		version="$(__gvm_map_version_hint_to_tag "${hint}" available)" || version=""
+	fi
+	[[ -n "${version}" ]] || return $(display_error "can not find a go version match ${hint}")
 
-		display_message "$mod_ver does not exist, try to install..."
-		$GVM_ROOT/scripts/install $mod_ver
+	display_message "go.mod requests ${hint}; using ${version}"
 
-		if [ $? -ne 0 ]; then
-			return $(display_error "gvm install $mod_ver error")
+	if [[ ! -d "${GVM_ROOT}/gos/${version}" ]]; then
+		display_message "${version} does not exist, try to install..."
+		"$GVM_ROOT/scripts/install" "${version}"
+		if [[ $? -ne 0 ]]; then
+			return $(display_error "gvm install ${version} error")
 		fi
 	fi
 
-	gvm_use "$mod_ver"
-
-}
+	gvm_use "${version}"
+}

scripts/env/use

@@ -14,6 +14,7 @@
 # <pre>@textblock</pre>
 #   Usage: gvm use [--version] <value> [--pkgset <value>] [--default]
 #          gvm use <version-name>@<pkgset-name> [--default]
+#          gvm use [--pkgset <value>] [--default]   # auto-detect from .go-version / go.mod
 #
 #   Options:
 #     --version value       version name
@@ -22,7 +23,8 @@
 #     --quiet               suppress 'now using' acknowledgements
 #     -h, --help            show this message
 #
-#   When using --pkgset, you must also specify a go version name.
+#   With no version, resolve from the nearest .go-version (preferred) or go.mod.
+#   When using --pkgset, you must also specify a go version name (or auto-detect).
 # @/textblock</pre>
 # @param args Variable list of options and values
 # @return Returns success (status 0) if a pkgset was selected successfully or
@@ -138,6 +140,7 @@ gvm_use() {
         then
             echo "Usage: gvm use [--version] <value> [--pkgset <value>] [--default]"
             echo "       gvm use <version-name>@<pkgset-name> [--default]"
+            echo "       gvm use [--pkgset <value>] [--default]"
             echo
             echo "Options:"
             echo "  --version value       go version name or alias"
@@ -146,7 +149,9 @@ gvm_use() {
             echo "  --quiet               suppress 'now using' acknowledgements"
             echo "  -h, --help            show this message"
             echo
-            echo "When using --pkgset, you must also specify a go version name."
+            echo "With no version, resolve from the nearest .go-version or go.mod"
+            echo "(toolchain / go directive; language versions map to the latest"
+            echo "installed patch for that minor)."
             echo
             return 0
         else
@@ -194,8 +199,14 @@ gvm_use() {
 
     if [[ -z "${version}" ]]
     then
-        display_error "Please specify the version. Execute 'gvm use --help' for command help."
-        return 1
+        # Bare `gvm use`: resolve from .go-version / go.mod (#10 / moovweb/gvm#523).
+        version="$(__gvm_resolve_project_go_version installed)" || version=""
+        if [[ -z "${version}" ]]
+        then
+            display_error "Please specify the version (or add .go-version / go.mod). Execute 'gvm use --help' for command help."
+            return 1
+        fi
+        [[ "${GVM_DEBUG}" -eq 1 ]] && echo "Auto-detected version: ${version}"
     fi
 
     # Exact match first, then prefix match — avoid fragile multi-grep pipelines under `set -e`.

scripts/function/_bash_pseudo_hash

@@ -42,7 +42,8 @@ setValueForKeyFakeAssocArray() {
     fi
     # parameter list supports empty arguments!
     local target_key="$1"; shift
-    local new_value="$1"; shift # @todo: need to support setting nil values!
+    # Empty values are stored as empty strings (no distinct nil). Callers use -n checks.
+    local new_value="$1"; shift
     local target_ary; target_ary=()
     local defaultIFS="$IFS"
     local IFS="$defaultIFS"
@@ -137,7 +138,8 @@ valueForKeyFakeAssocArray() {
     local _item
     for _item in "${target_ary[@]}"; do
         if [[ "${_item%%:*}" == "${target_key}" ]]; then
-          value="$(_decode "${_item#*:}")" # @todo: need to support returning nil values!
+          # Missing keys and empty values both surface as "" (no distinct nil).
+          value="$(_decode "${_item#*:}")"
           break
         fi
     done

scripts/function/find_path_upwards

@@ -1,5 +1,9 @@
 #!/usr/bin/env bash
 
+. "$GVM_ROOT/scripts/function/_shell_compat" || return 1
+# Canonical walker lives here; load eagerly so cd / use share one implementation.
+. "$GVM_ROOT/scripts/function/resolve_project_version" || return 1
+
 # __gvm_find_path_upwards()
 # /*!
 # @abstract Search upwards through the directory tree for a target file or
@@ -30,52 +34,14 @@ __gvm_find_path_upwards() {
         echo "" && return 1
     fi
 
-    local found_file="$(__gvmp_find_current_path_for_target "${target}")"
-    echo "${found_file}"
-
-    if [[ -z "${found_file}" ]]; then
-        return 1
-    fi
-
-    return 0
+    __gvm_find_file_upwards "${target}" "${start_dir}" "${final_dir}"
 }
 
+# Compatibility alias for older call sites / tests.
 __gvmp_find_path_for_target() {
-    local target="${1}"
-    local start_dir="${2}"
-    local final_dir="${3}"
-
-    if [[ ${#target} -eq 0 ]]; then
-        echo ""; return 1
-    fi
-
-    # resolve tilde for HOME
-    start_dir="${start_dir/#\~/$HOME}"
-
-    # resolve dot for PWD
-    if [[ "${start_dir}" == "." ]]; then
-        start_dir="$PWD"
-    fi
-
-    local current_dir="${start_dir}"
-    local highest_dir="${final_dir}"
-
-    builtin cd "${current_dir}"
-    while [[ "${current_dir}" != "${highest_dir}" && "${current_dir}" != "/" ]]; do
-        if [[ -f "${current_dir}/${target}" ||  -d "${current_dir}/${target}" ]]; then
-            echo "${current_dir}/${target}"; return 0
-            break
-        fi
-
-        builtin cd ..
-        current_dir="$(pwd)"
-    done
-
-    echo "";
-    return 1
+    __gvm_find_file_upwards "$@"
 }
 
-
 __gvmp_find_current_path_for_target() {
     local target="${1}"
     local start_dir="$PWD"
@@ -94,4 +60,4 @@ __gvmp_find_current_path_for_target() {
 
     echo "";
     return 1
-}
+}