From bbb16e4e72c58d43aa1ee356cb974d669a0a02fe Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Tue, 30 Sep 2025 10:55:42 -0700
Subject: [PATCH] drive: don't use regexp package in leaf types package

Even with ts_omit_drive, the drive package is currently still imported
for some types. So it should be light. But it was depending on the
"regexp" packge, which I'd like to remove from our minimal builds.

Updates #12614

Change-Id: I5bf85d8eb15a739793723b1da11c370d3fcd2f32
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
---
 drive/remote.go | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drive/remote.go b/drive/remote.go
index 9aeead710..2c6fba894 100644
--- a/drive/remote.go
+++ b/drive/remote.go
@@ -9,7 +9,6 @@ import (
 	"bytes"
 	"errors"
 	"net/http"
-	"regexp"
 	"strings"
 )
 
@@ -21,10 +20,6 @@ var (
 	ErrInvalidShareName = errors.New("Share names may only contain the letters a-z, underscore _, parentheses (), or spaces")
 )
 
-var (
-	shareNameRegex = regexp.MustCompile(`^[a-z0-9_\(\) ]+$`)
-)
-
 // AllowShareAs reports whether sharing files as a specific user is allowed.
 func AllowShareAs() bool {
 	return !DisallowShareAs && doAllowShareAs()
@@ -125,9 +120,26 @@ func NormalizeShareName(name string) (string, error) {
 	// Trim whitespace
 	name = strings.TrimSpace(name)
 
-	if !shareNameRegex.MatchString(name) {
+	if !validShareName(name) {
 		return "", ErrInvalidShareName
 	}
 
 	return name, nil
 }
+
+func validShareName(name string) bool {
+	if name == "" {
+		return false
+	}
+	for _, r := range name {
+		if 'a' <= r && r <= 'z' || '0' <= r && r <= '9' {
+			continue
+		}
+		switch r {
+		case '_', ' ', '(', ')':
+			continue
+		}
+		return false
+	}
+	return true
+}