Reduce duplication in history path construction (#13475)

# Description
Currently there is a bit of chaos regarding construction of history file
paths. Various pieces of code across a number of crates reimplement the
same/similar logic:
- There is `get_history_path`, but it requires a directory parameter (it
really just joins it with a file name).
- Some places use a const for the directory parameter, others use a
string literal - in all cases the value seems to be `"nushell"`.
- Some places assume the `"nushell"` value, other plumb it down from
close to the top of the call stack.
- Some places use a constant for history file names while others assume
it.

This PR tries to make it so that the history/config path format is
defined in a single places and so dependencies on it are easier to
follow:
- It removes `get_history_path` and adds a `file_path` method to
`HistoryConfig` instead (an extra motivation being, this is a convenient
place that can be used from all creates that need a history file path)
- Adds a `nu_config_dir` function that returns the nushell configuration
directory.
- Updates existing code to rely on the above, effectively removing
duplicate uses of `"nushell"` and `NUSHELL_FOLDER` and assumptions about
file names associated with different history formats

# User-Facing Changes
None

src/config_files.rs

@@ -17,7 +17,6 @@ use std::{
     sync::Arc,
 };
 
-pub(crate) const NUSHELL_FOLDER: &str = "nushell";
 const CONFIG_FILE: &str = "config.nu";
 const ENV_FILE: &str = "env.nu";
 const LOGINSHELL_FILE: &str = "login.nu";
@@ -48,9 +47,7 @@ pub(crate) fn read_config_file(
                 report_shell_error(engine_state, &e);
             }
         }
-    } else if let Some(mut config_path) = nu_path::config_dir() {
-        config_path.push(NUSHELL_FOLDER);
-
+    } else if let Some(mut config_path) = nu_path::nu_config_dir() {
         // Create config directory if it does not exist
         if !config_path.exists() {
             if let Err(err) = std::fs::create_dir_all(&config_path) {
@@ -141,8 +138,7 @@ pub(crate) fn read_loginshell_file(engine_state: &mut EngineState, stack: &mut S
     );
 
     // read and execute loginshell file if exists
-    if let Some(mut config_path) = nu_path::config_dir() {
-        config_path.push(NUSHELL_FOLDER);
+    if let Some(mut config_path) = nu_path::nu_config_dir() {
         config_path.push(LOGINSHELL_FILE);
 
         warn!("loginshell_file: {}", config_path.display());
@@ -268,16 +264,11 @@ pub(crate) fn setup_config(
         &config_file, &env_file, is_login_shell
     );
 
-    let ask_to_create_config = if let Some(mut config_path) = nu_path::config_dir() {
-        config_path.push(NUSHELL_FOLDER);
-        !config_path.exists()
-    } else {
-        false
-    };
+    let ask_to_create_config = nu_path::nu_config_dir().map_or(false, |p| !p.exists());
 
     let result = catch_unwind(AssertUnwindSafe(|| {
         #[cfg(feature = "plugin")]
-        read_plugin_file(engine_state, plugin_file, NUSHELL_FOLDER);
+        read_plugin_file(engine_state, plugin_file);
 
         read_config_file(engine_state, stack, env_file, true, ask_to_create_config);
         read_config_file(
@@ -315,8 +306,7 @@ pub(crate) fn set_config_path(
     );
     let config_path = match config_file {
         Some(s) => canonicalize_with(&s.item, cwd).ok(),
-        None => nu_path::config_dir().map(|mut p| {
-            p.push(NUSHELL_FOLDER);
+        None => nu_path::nu_config_dir().map(|p| {
             let mut p = canonicalize_with(&p, cwd).unwrap_or(p.into());
             p.push(default_config_name);
             canonicalize_with(&p, cwd).unwrap_or(p)

src/main.rs

@@ -98,14 +98,7 @@ fn main() -> Result<()> {
     // Set default NU_LIB_DIRS and NU_PLUGIN_DIRS here before the env.nu is processed. If
     // the env.nu file exists, these values will be overwritten, if it does not exist, or
     // there is an error reading it, these values will be used.
-    let nushell_config_path = if let Some(mut path) = nu_path::config_dir() {
-        path.push("nushell");
-        path.into()
-    } else {
-        // Not really sure what to default this to if nu_path::config_dir() returns None
-        std::path::PathBuf::new()
-    };
-
+    let nushell_config_path: PathBuf = nu_path::nu_config_dir().map(Into::into).unwrap_or_default();
     if let Ok(xdg_config_home) = std::env::var("XDG_CONFIG_HOME") {
         if !xdg_config_home.is_empty() {
             if nushell_config_path

src/run.rs

@@ -1,6 +1,6 @@
 use crate::{
     command,
-    config_files::{self, setup_config, NUSHELL_FOLDER},
+    config_files::{self, setup_config},
 };
 use log::trace;
 #[cfg(feature = "plugin")]
@@ -21,16 +21,11 @@ pub(crate) fn run_commands(
     entire_start_time: std::time::Instant,
 ) {
     trace!("run_commands");
-    let mut stack = Stack::new();
+
     let start_time = std::time::Instant::now();
+    let ask_to_create_config = nu_path::nu_config_dir().map_or(false, |p| !p.exists());
 
-    let ask_to_create_config = if let Some(mut config_path) = nu_path::config_dir() {
-        config_path.push(NUSHELL_FOLDER);
-        !config_path.exists()
-    } else {
-        false
-    };
-
+    let mut stack = Stack::new();
     if stack.has_env_var(engine_state, "NU_DISABLE_IR") {
         stack.use_ir = false;
     }
@@ -42,7 +37,7 @@ pub(crate) fn run_commands(
     // if the --no-config-file(-n) flag is passed, do not load plugin, env, or config files
     if parsed_nu_cli_args.no_config_file.is_none() {
         #[cfg(feature = "plugin")]
-        read_plugin_file(engine_state, parsed_nu_cli_args.plugin_file, NUSHELL_FOLDER);
+        read_plugin_file(engine_state, parsed_nu_cli_args.plugin_file);
 
         perf!("read plugins", start_time, use_color);
 
@@ -63,12 +58,7 @@ pub(crate) fn run_commands(
         perf!("read env.nu", start_time, use_color);
 
         let start_time = std::time::Instant::now();
-        let ask_to_create_config = if let Some(mut config_path) = nu_path::config_dir() {
-            config_path.push(config_files::NUSHELL_FOLDER);
-            !config_path.exists()
-        } else {
-            false
-        };
+        let ask_to_create_config = nu_path::nu_config_dir().map_or(false, |p| !p.exists());
 
         // If we have a config file parameter *OR* we have a login shell parameter, read the config file
         if parsed_nu_cli_args.config_file.is_some() || parsed_nu_cli_args.login_shell.is_some() {
@@ -140,14 +130,9 @@ pub(crate) fn run_file(
     // if the --no-config-file(-n) flag is passed, do not load plugin, env, or config files
     if parsed_nu_cli_args.no_config_file.is_none() {
         let start_time = std::time::Instant::now();
-        let ask_to_create_config = if let Some(mut config_path) = nu_path::config_dir() {
-            config_path.push(config_files::NUSHELL_FOLDER);
-            !config_path.exists()
-        } else {
-            false
-        };
+        let ask_to_create_config = nu_path::nu_config_dir().map_or(false, |p| !p.exists());
         #[cfg(feature = "plugin")]
-        read_plugin_file(engine_state, parsed_nu_cli_args.plugin_file, NUSHELL_FOLDER);
+        read_plugin_file(engine_state, parsed_nu_cli_args.plugin_file);
         perf!("read plugins", start_time, use_color);
 
         let start_time = std::time::Instant::now();
@@ -230,7 +215,6 @@ pub(crate) fn run_repl(
     let ret_val = evaluate_repl(
         engine_state,
         stack,
-        NUSHELL_FOLDER,
         parsed_nu_cli_args.execute,
         parsed_nu_cli_args.no_std_lib,
         entire_start_time,