Add unlet_env command (#3629)

* Add ability to remove env variables

Signed-off-by: nathom <nathanthomas707@gmail.com>

* Implement unlet_env command

Signed-off-by: nathom <nathanthomas707@gmail.com>

* Update parameter description

Signed-off-by: nathom <nathanthomas707@gmail.com>

* Migrate to new filestructure

Signed-off-by: nathom <nathanthomas707@gmail.com>

* Added tests for unlet-env

Signed-off-by: nathom <nathanthomas707@gmail.com>

* Formatting

Signed-off-by: nathom <nathanthomas707@gmail.com>

crates/nu-command/src/commands/env/mod.rs

@@ -3,6 +3,7 @@ mod autoenv_trust;
 mod autoenv_untrust;
 mod let_env;
 mod load_env;
+mod unlet_env;
 mod with_env;
 
 pub use autoenv::Autoenv;
@@ -10,4 +11,5 @@ pub use autoenv_trust::AutoenvTrust;
 pub use autoenv_untrust::AutoenvUntrust;
 pub use let_env::LetEnv;
 pub use load_env::LoadEnv;
+pub use unlet_env::UnletEnv;
 pub use with_env::WithEnv;

crates/nu-command/src/commands/env/unlet_env.rs

@@ -0,0 +1,59 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+
+use nu_errors::ShellError;
+use nu_protocol::{Signature, SyntaxShape};
+use nu_source::Tagged;
+
+pub struct UnletEnv;
+
+#[derive(Deserialize)]
+pub struct UnletEnvArgs {
+    pub name: Tagged<String>,
+}
+
+impl WholeStreamCommand for UnletEnv {
+    fn name(&self) -> &str {
+        "unlet-env"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("unlet-env").required(
+            "name",
+            SyntaxShape::String,
+            "the name of the environment variable",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Delete an environment variable."
+    }
+
+    fn run_with_actions(&self, args: CommandArgs) -> Result<ActionStream, ShellError> {
+        unlet_env(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Remove the environment variable named FOO.",
+            example: "unlet-env FOO",
+            result: None,
+        }]
+    }
+}
+
+pub fn unlet_env(args: CommandArgs) -> Result<ActionStream, ShellError> {
+    let ctx = &args.context;
+
+    let name: Tagged<String> = args.req(0)?;
+
+    if ctx.scope.remove_env_var(&name.item) == None {
+        return Err(ShellError::labeled_error(
+            "Not an environment variable. Run `echo $nu.env` to view the available variables.",
+            "not an environment variable",
+            name.span(),
+        ));
+    }
+
+    Ok(ActionStream::empty())
+}

crates/nu-command/src/default_context.rs

@@ -13,6 +13,7 @@ pub fn create_default_context(interactive: bool) -> Result<EvaluationContext, Bo
             whole_stream_command(NuPlugin),
             whole_stream_command(Let),
             whole_stream_command(LetEnv),
+            whole_stream_command(UnletEnv),
             whole_stream_command(LoadEnv),
             whole_stream_command(Def),
             whole_stream_command(Source),

crates/nu-engine/src/evaluate/scope.rs

@@ -239,6 +239,15 @@ impl Scope {
         }
     }
 
+    pub fn remove_env_var(&self, name: impl Into<String>) -> Option<String> {
+        if let Some(frame) = self.frames.lock().last_mut() {
+            if let Some(val) = frame.env.remove_entry(&name.into()) {
+                return Some(val.1);
+            }
+        }
+        None
+    }
+
     pub fn add_env(&self, env_vars: IndexMap<String, String>) {
         if let Some(frame) = self.frames.lock().last_mut() {
             frame.env.extend(env_vars)

tests/shell/pipeline/commands/internal.rs

@@ -411,6 +411,31 @@ fn let_env_variable() {
     assert_eq!(actual.out, "hello world");
 }
 
+#[test]
+fn unlet_env_variable() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+            let-env TEST_VAR = "hello world"
+            unlet-env TEST_VAR
+            echo $nu.env.TEST_VAR
+        "#
+    );
+    assert!(actual.err.contains("did you mean"));
+}
+
+#[test]
+fn unlet_nonexistent_variable() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+            unlet-env NONEXISTENT_VARIABLE
+        "
+    );
+
+    assert!(actual.err.contains("did you mean"));
+}
+
 #[test]
 fn let_env_doesnt_leak() {
     let actual = nu!(