Do not pass non-string env vars to externals (#4748)

* Do not pass non-string env vars to externals

Also misc cleanup

* Add note to default config

* Add a test

* Ensure PATH/Path conversion list <-> string

crates/nu-command/src/env/env_command.rs

@@ -1,7 +1,9 @@
 use nu_engine::env_to_string;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, IntoPipelineData, PipelineData, Signature, Value};
+use nu_protocol::{
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Value,
+};
 
 #[derive(Clone)]
 pub struct Env;
@@ -27,7 +29,6 @@ impl Command for Env {
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
         let span = call.head;
-        let config = stack.get_config().unwrap_or_default();
 
         let mut env_vars: Vec<(String, Value)> =
             stack.get_env_vars(engine_state).into_iter().collect();
@@ -39,7 +40,12 @@ impl Command for Env {
             let mut cols = vec![];
             let mut vals = vec![];
 
-            let raw = env_to_string(&name, val.clone(), engine_state, stack, &config)?;
+            let raw_val = match env_to_string(&name, &val, engine_state, stack) {
+                Ok(raw) => Value::string(raw, span),
+                Err(ShellError::EnvVarNotAString(..)) => Value::nothing(span),
+                Err(e) => return Err(e),
+            };
+
             let val_type = val.get_type();
 
             cols.push("name".into());
@@ -52,7 +58,7 @@ impl Command for Env {
             vals.push(val);
 
             cols.push("raw".into());
-            vals.push(Value::string(raw, span));
+            vals.push(raw_val);
 
             values.push(Value::Record { cols, vals, span });
         }

crates/nu-command/src/system/exec.rs

@@ -76,8 +76,7 @@ fn exec(
     let args: Vec<Spanned<String>> = call.rest(engine_state, stack, 1)?;
 
     let cwd = current_dir(engine_state, stack)?;
-    let config = stack.get_config()?;
-    let env_vars = env_to_strings(engine_state, stack, &config)?;
+    let env_vars = env_to_strings(engine_state, stack)?;
     let current_dir = current_dir(engine_state, stack)?;
 
     let external_command = ExternalCommand {

crates/nu-command/src/system/run_external.rs

@@ -55,8 +55,7 @@ impl Command for External {
         let redirect_stderr = call.has_flag("redirect-stderr");
 
         // Translate environment variables from Values to Strings
-        let config = stack.get_config().unwrap_or_default();
-        let env_vars_str = env_to_strings(engine_state, stack, &config)?;
+        let env_vars_str = env_to_strings(engine_state, stack)?;
 
         fn value_as_spanned(value: Value) -> Result<Spanned<String>, ShellError> {
             let span = value.span()?;

crates/nu-command/src/viewers/griddle.rs

@@ -66,7 +66,7 @@ prints out the list properly."#
         let separator_param: Option<String> = call.get_flag(engine_state, stack, "separator")?;
         let config = stack.get_config().unwrap_or_default();
         let env_str = match stack.get_env_var(engine_state, "LS_COLORS") {
-            Some(v) => Some(env_to_string("LS_COLORS", v, engine_state, stack, &config)?),
+            Some(v) => Some(env_to_string("LS_COLORS", &v, engine_state, stack)?),
             None => None,
         };
         let use_grid_icons = config.use_grid_icons;