From 0113661c81a0584028637ec4c7d5e583a8c18085 Mon Sep 17 00:00:00 2001
From: Chris Gillespie <6572184+gillespiecd@users.noreply.github.com>
Date: Mon, 9 Nov 2020 08:23:41 -0800
Subject: [PATCH] Flag to clear history file (#2720)

---
 crates/nu-cli/src/cli.rs              |  7 +++
 crates/nu-cli/src/commands/history.rs | 61 ++++++++++++++++++---------
 2 files changed, 47 insertions(+), 21 deletions(-)

diff --git a/crates/nu-cli/src/cli.rs b/crates/nu-cli/src/cli.rs
index 8da97bc1ce..6c05df65ce 100644
--- a/crates/nu-cli/src/cli.rs
+++ b/crates/nu-cli/src/cli.rs
@@ -323,6 +323,7 @@ pub async fn run_vec_of_pipelines(
 #[cfg(feature = "rustyline-support")]
 fn convert_rustyline_result_to_string(input: Result<String, ReadlineError>) -> LineResult {
     match input {
+        Ok(s) if s == "history -c" || s == "history --clear" => LineResult::ClearHistory,
         Ok(s) => LineResult::Success(s),
         Err(ReadlineError::Interrupted) => LineResult::CtrlC,
         Err(ReadlineError::Eof) => LineResult::CtrlD,
@@ -499,6 +500,11 @@ pub async fn cli(mut context: EvaluationContext) -> Result<(), Box<dyn Error>> {
                 context.maybe_print_errors(Text::from(line));
             }
 
+            LineResult::ClearHistory => {
+                rl.clear_history();
+                let _ = rl.save_history(&history_path);
+            }
+
             LineResult::Error(line, err) => {
                 rl.add_history_entry(&line);
                 let _ = rl.save_history(&history_path);
@@ -848,6 +854,7 @@ pub enum LineResult {
     Break,
     CtrlC,
     CtrlD,
+    ClearHistory,
 }
 
 pub async fn parse_and_eval(line: &str, ctx: &mut EvaluationContext) -> Result<String, ShellError> {
diff --git a/crates/nu-cli/src/commands/history.rs b/crates/nu-cli/src/commands/history.rs
index 5b5b963e1f..586efee6b1 100644
--- a/crates/nu-cli/src/commands/history.rs
+++ b/crates/nu-cli/src/commands/history.rs
@@ -27,6 +27,11 @@ pub fn history_path(config: &dyn Conf) -> PathBuf {
         })
 }
 
+#[derive(Deserialize)]
+struct Arguments {
+    clear: Option<bool>,
+}
+
 pub struct History;
 
 #[async_trait]
@@ -36,7 +41,7 @@ impl WholeStreamCommand for History {
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("history")
+        Signature::build("history").switch("clear", "Clears out the history entries", Some('c'))
     }
 
     fn usage(&self) -> &str {
@@ -48,31 +53,45 @@ impl WholeStreamCommand for History {
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        history(args, registry)
+        history(args, registry).await
     }
 }
 
-fn history(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+async fn history(
+    args: CommandArgs,
+    _registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
     let config: Box<dyn Conf> = Box::new(NuConfig::new());
-    let tag = args.call_info.name_tag;
-    let path = history_path(&config);
-    let file = File::open(path);
-    if let Ok(file) = file {
-        let reader = BufReader::new(file);
-        let output = reader.lines().filter_map(move |line| match line {
-            Ok(line) => Some(ReturnSuccess::value(
-                UntaggedValue::string(line).into_value(tag.clone()),
-            )),
-            Err(_) => None,
-        });
+    let tag = args.call_info.name_tag.clone();
+    let (Arguments { clear }, _) = args.process(&_registry).await?;
 
-        Ok(futures::stream::iter(output).to_output_stream())
-    } else {
-        Err(ShellError::labeled_error(
-            "Could not open history",
-            "history file could not be opened",
-            tag,
-        ))
+    let path = history_path(&config);
+
+    match clear {
+        Some(_) => {
+            // This is a NOOP, the logic to clear is handled in cli.rs
+            Ok(OutputStream::empty())
+        }
+        None => {
+            if let Ok(file) = File::open(path) {
+                let reader = BufReader::new(file);
+                // Skips the first line, which is a Rustyline internal
+                let output = reader.lines().skip(1).filter_map(move |line| match line {
+                    Ok(line) => Some(ReturnSuccess::value(
+                        UntaggedValue::string(line).into_value(tag.clone()),
+                    )),
+                    Err(_) => None,
+                });
+
+                Ok(futures::stream::iter(output).to_output_stream())
+            } else {
+                Err(ShellError::labeled_error(
+                    "Could not open history",
+                    "history file could not be opened",
+                    tag,
+                ))
+            }
+        }
     }
 }