From ebce62629e9f6fa3d68ba13f27d5d672997f7850 Mon Sep 17 00:00:00 2001
From: Rikuki IX <52599939+rikukiix@users.noreply.github.com>
Date: Fri, 13 Dec 2024 01:19:03 +0800
Subject: [PATCH] fix: make exec command decrement SHLVL correctly (#14570)

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# Description
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fixes #14567

Now NuShell's `exec` command will decrement `SHLVL` env value before
passing it to target executable.

It only works in interactive session, the same as `SHLVL`
initialization.

In addition, this PR also make a simple change to `SHLVL` initialization
(only remove an unnecessary type conversion).

# User-Facing Changes
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helps us keep track of breaking changes. -->

None.

# Tests + Formatting
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Formatted.

With interactively tested with several shells (bash, zsh, fish) and
cross-exec-ing them, it works well this time.

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---
 crates/nu-command/src/system/exec.rs | 10 ++++++++++
 src/main.rs                          |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/crates/nu-command/src/system/exec.rs b/crates/nu-command/src/system/exec.rs
index 8a2b24a113..e9f49b86c1 100644
--- a/crates/nu-command/src/system/exec.rs
+++ b/crates/nu-command/src/system/exec.rs
@@ -61,6 +61,16 @@ On Windows based systems, Nushell will wait for the command to finish and then e
         let envs = env_to_strings(engine_state, stack)?;
         command.env_clear();
         command.envs(envs);
+        // Decrement SHLVL as removing the current shell from the stack
+        // (only works in interactive mode, same as initialization)
+        if engine_state.is_interactive {
+            if let Some(shlvl) = engine_state.get_env_var("SHLVL") {
+                let shlvl = shlvl.as_int().unwrap_or(1) - 1;
+                command.env("SHLVL", shlvl.to_string());
+            } else {
+                command.env("SHLVL", "0");
+            }
+        }
 
         // Configure args.
         let args = crate::eval_arguments_from_call(engine_state, stack, call)?;
diff --git a/src/main.rs b/src/main.rs
index 7d39aef02b..db55db3ff2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -325,7 +325,7 @@ fn main() -> Result<()> {
     if engine_state.is_interactive {
         let mut shlvl = engine_state
             .get_env_var("SHLVL")
-            .map(|x| x.as_str().unwrap_or("0").parse::<i64>().unwrap_or(0))
+            .map(|x| x.as_int().unwrap_or(0))
             .unwrap_or(0);
         shlvl += 1;
         engine_state.add_env_var("SHLVL".to_string(), Value::int(shlvl, Span::unknown()));