From dad8c527e0518b1fc9ff3a4da4d1b6020c45ac35 Mon Sep 17 00:00:00 2001
From: Fabian Boehm <FHomborg@gmail.com>
Date: Fri, 13 Jan 2023 17:56:28 +0100
Subject: [PATCH] read: Error on read-only variables

Fixes #9346
---
 src/builtins/read.cpp  | 5 +++++
 tests/checks/read.fish | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/builtins/read.cpp b/src/builtins/read.cpp
index 0e7574b41..72b176af8 100644
--- a/src/builtins/read.cpp
+++ b/src/builtins/read.cpp
@@ -424,6 +424,11 @@ static int validate_read_args(const wchar_t *cmd, read_cmd_opts_t &opts, int arg
             builtin_print_error_trailer(parser, streams.err, cmd);
             return STATUS_INVALID_ARGS;
         }
+        if (env_var_t::flags_for(argv[i]) & env_var_t::flag_read_only) {
+            streams.err.append_format(_(L"%ls: %ls: cannot overwrite read-only variable"), cmd, argv[i]);
+            builtin_print_error_trailer(parser, streams.err, cmd);
+            return STATUS_INVALID_ARGS;
+        }
     }
 
     return STATUS_CMD_OK;
diff --git a/tests/checks/read.fish b/tests/checks/read.fish
index 709ee977b..1172a6e70 100644
--- a/tests/checks/read.fish
+++ b/tests/checks/read.fish
@@ -380,3 +380,12 @@ begin
 end | read -l --line foo bar
 echo $foo $bar
 # CHECK: 1 2
+
+echo foo | read status
+# CHECKERR: read: status: cannot overwrite read-only variable
+# CHECKERR: {{.*}}read.fish (line {{\d+}}):
+# CHECKERR: echo foo | read status
+# CHECKERR: ^
+# CHECKERR: (Type 'help read' for related documentation)
+echo read $status
+# CHECK: read 2