From 260bd42edbb4049a7e6ab033d2674d42738d8cd4 Mon Sep 17 00:00:00 2001
From: Hasnain Lakhani <hasnain.lakhani@databricks.com>
Date: Fri, 5 Jan 2024 15:07:15 -0800
Subject: [PATCH 1/2] working

---
 src/env.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/env.rs b/src/env.rs
index fe59f3d..17ce3d6 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -189,8 +189,30 @@ impl Env {
         }
     }
 
+    // a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character. Max length is 63.
+    fn validate_rfc_1123_label(label: &str) -> bool {
+        if label.is_empty() || label.len() > 63 {
+            return false;
+        }
+        label
+            .chars()
+            .all(|c| (c.is_ascii_lowercase() && c.is_ascii_alphanumeric()) || c == '-')
+            && label.chars().next().unwrap().is_ascii_alphanumeric()
+            && label.chars().last().unwrap().is_ascii_alphanumeric()
+    }
+
     pub fn set_namespace(&mut self, namespace: Option<&str>) {
         let mut do_clear = false;
+        if let Some(ns) = namespace {
+            if !Env::validate_rfc_1123_label(ns) {
+                clickwriteln!(
+                    io::stderr(),
+                    "Invalid namespace name. Namespaces must be valid RFC 1123 labels (less than 64 characters, lowercase alphanumeric or '-', and start and end with an alphanumeric character)"
+                );
+                io::stdout().flush().expect("Could not flush stdout");
+                return;
+            }
+        }
         if let (Some(my_ns), Some(new_ns)) = (&self.namespace, namespace) {
             if my_ns.as_str() != new_ns {
                 do_clear = true; // need to use bool since self is borrowed here

From 33ff590207a2e554f1e1651fdd12a538e15b3bee Mon Sep 17 00:00:00 2001
From: Hasnain Lakhani <hasnain.lakhani@databricks.com>
Date: Fri, 5 Jan 2024 15:32:47 -0800
Subject: [PATCH 2/2] don't need to flush stdout

---
 src/env.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/env.rs b/src/env.rs
index 17ce3d6..2e70413 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -209,7 +209,6 @@ impl Env {
                     io::stderr(),
                     "Invalid namespace name. Namespaces must be valid RFC 1123 labels (less than 64 characters, lowercase alphanumeric or '-', and start and end with an alphanumeric character)"
                 );
-                io::stdout().flush().expect("Could not flush stdout");
                 return;
             }
         }