As per: twpayne#3141

assets/chezmoi.io/docs/reference/templates/functions/lookPathIn.md

@@ -0,0 +1,39 @@
+# `lookPathIn` *file* *paths*
+
+`lookPathIn` searches for an executable named *file* in the directories provided by
+the `paths` parameter using the standard OS way of separating the PATH environment
+variable. The result may be an absolute path or a path relative to the current directory.
+If *file* is not found, `lookPathIn` returns an empty string.
+
+If the OS is Windows `lookPathIn` will either: if there is an extension, check to see if
+the extension is specified in the `PathExt` environment variable. If there isn't an
+extension it will try each of the extensions specified in the `PathExt` environment
+variable in the order provided until it finds one. In either case if it doesn't `lookPathIn`
+moves onto the next path provided in the `paths` parameter.
+
+`lookPathIn` is provided as an alternative to `lookPath` so that you interrogate the
+paths as you would have them.
+
+Each successful lookup is cached based on the full path, and evaluated in the correct
+order each time to reduce `File Stat` operations.
+
+!!! example
+
+    ```
+        {{- $paths := list }}
+        {{- $homeDir := .chezmoi.homeDir }}
+        {{- range $_, $relPath := list "bin" "go/bin" ".cargo/bin" ".local/bin" }}
+        {{    $path := joinPath $homeDir $relPath }}
+        {{-   if stat $path }}
+        {{-     $paths = mustAppend $paths $path }}
+        {{-   end }}
+        {{- end }}
+        {{- if $paths }}
+        export PATH={{ toStrings $paths | join ":" }}:$PATH
+        {{- end }}
+
+        {{ if lookPath "less" $paths }}
+        echo "Good news we have found 'less' on system at '{{ lookPath "less" $paths }}'!"
+        export DIFFTOOL=less
+        {{ end }}
+    ```

assets/chezmoi.io/mkdocs.yml

@@ -198,6 +198,7 @@ nav:
       - joinPath: reference/templates/functions/joinPath.md
       - jq: reference/templates/functions/jq.md
       - lookPath: reference/templates/functions/lookPath.md
+      - lookPathIn: reference/templates/functions/lookPathIn.md
       - lstat: reference/templates/functions/lstat.md
       - mozillaInstallHash: reference/templates/functions/mozillaInstallHash.md
       - output: reference/templates/functions/output.md

internal/chezmoi/chezmoi_unix.go

@@ -15,6 +15,11 @@ func init() {
 	unix.Umask(int(Umask))
 }
 
+// findExecutableExtensions returns valid OS executable extensions, on unix it can be anything
+func findExecutableExtensions(path string) []string {
+	return []string{path}
+}
+
 // isExecutable returns if fileInfo is executable.
 func isExecutable(fileInfo fs.FileInfo) bool {
 	return fileInfo.Mode().Perm()&0o111 != 0

internal/chezmoi/chezmoi_windows.go

@@ -2,13 +2,51 @@ package chezmoi
 
 import (
 	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
 )
 
 const nativeLineEnding = "\r\n"
 
-// isExecutable returns false on Windows.
+var (
+	pathExt []string = nil
+)
+
+// findExecutableExtensions returns valid OS executable extensions for a given executable
+func findExecutableExtensions(path string) []string {
+	cmdExt := filepath.Ext(path)
+	if cmdExt != "" {
+		return []string{path}
+	}
+	result := make([]string, len(cmdExt))
+	for i, e := range getPathExt() {
+		result[i] = path + e
+	}
+	return result
+}
+
+func getPathExt() []string {
+	if pathExt == nil {
+		pathExt = strings.Split(os.Getenv("PathExt"), string(filepath.ListSeparator))
+	}
+	return pathExt
+}
+
+// isExecutable checks if the file has an extension listed in the `PathExt` variable as per:
+// https://www.nextofwindows.com/what-is-pathext-environment-variable-in-windows then checks to see if it's regular file
 func isExecutable(fileInfo fs.FileInfo) bool {
-	return false
+	foundPathExt := false
+	cmdExt := filepath.Ext(fileInfo.Name())
+	if cmdExt != "" {
+		for _, ext := range getPathExt() {
+			if strings.EqualFold(cmdExt, ext) {
+				foundPathExt = true
+				break
+			}
+		}
+	}
+	return foundPathExt && fileInfo.Mode().IsRegular()
 }
 
 // isPrivate returns false on Windows.

internal/chezmoi/lookpathin.go

@@ -0,0 +1,48 @@
+package chezmoi
+
+import (
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+var (
+	foundExecutableCacheMutex sync.Mutex
+	foundExecutableCache      = make(map[string]struct{})
+)
+
+// LookPathIn is like lookPath except that you can specify the paths rather than just using the current `$PATH`. This
+// makes it useful for the resulting path of rc/profile files.
+func LookPathIn(file string, paths string) (string, error) {
+
+	foundExecutableCacheMutex.Lock()
+	defer foundExecutableCacheMutex.Unlock()
+
+	// stolen from: /usr/lib/go-1.20/src/os/exec/lp_unix.go:52
+	for _, dir := range filepath.SplitList(paths) {
+		if dir == "" {
+			continue
+		}
+		p := filepath.Join(dir, file)
+		for _, path := range findExecutableExtensions(p) {
+			if _, ok := foundExecutableCache[path]; ok {
+				return path, nil
+			}
+			f, err := os.Stat(file)
+			if err != nil {
+				continue
+			}
+			m := f.Mode()
+			// isExecutable doesn't care if it's a directory
+			if m.IsDir() {
+				continue
+			}
+			if isExecutable(f) {
+				foundExecutableCache[path] = struct{}{}
+				return path, nil
+			}
+		}
+	}
+
+	return "", nil
+}

internal/cmd/config.go

@@ -432,6 +432,7 @@ func newConfig(options ...configOption) (*Config, error) {
 		"lastpass":                 c.lastpassTemplateFunc,
 		"lastpassRaw":              c.lastpassRawTemplateFunc,
 		"lookPath":                 c.lookPathTemplateFunc,
+		"lookPathIn":               c.lookPathInTemplateFunc,
 		"lstat":                    c.lstatTemplateFunc,
 		"mozillaInstallHash":       c.mozillaInstallHashTemplateFunc,
 		"onepassword":              c.onepasswordTemplateFunc,

internal/cmd/templatefuncs.go

@@ -315,6 +315,16 @@ func (c *Config) lookPathTemplateFunc(file string) string {
 	}
 }
 
+func (c *Config) lookPathInTemplateFunc(file string, paths string) string {
+	switch path, err := chezmoi.LookPathIn(file, paths); {
+	case err == nil:
+		return path
+	// It's wrong to return an error past a parsing issue, parser is "dumb" however.
+	default:
+		panic(err)
+	}
+}
+
 func (c *Config) lstatTemplateFunc(name string) any {
 	switch fileInfo, err := c.fileSystem.Lstat(name); {
 	case err == nil:

internal/cmd/testdata/scripts/templatefuncs.txtar

@@ -72,6 +72,14 @@ stdout ^value$
 exec chezmoi execute-template '{{ lookPath "go" }}'
 stdout go$exe
 
+# test lookPathIn template function to find in specified script - success
+exec chezmoi execute-template '{{ lookPathIn "su" "/usr/bin" }}'
+stdout go$exe
+
+# test lookPathIn template function to find in specified script - failure
+exec chezmoi execute-template '{{ lookPathIn "su" "/lib" }}'
+stdout go$exe
+
 # test lookPath template function to check if file exists
 exec chezmoi execute-template '{{ lookPath "/non-existing-file" }}'
 ! stdout .