Remove wcstringutil::split_string()

It is short and simple enough to write yourself if you need it and it encourages
bad behavior by a) always returning owned strings, b) always allocating them in
a vector. If/where possible, it is better to a) use &wstr, b) use an iterator.

In rust, it's an anti-pattern to unnecessarily abstract over allocating
operations. Some of the call sites even called split_string(..).into_iter().

src/builtins/argparse.rs

@@ -4,7 +4,6 @@ use super::prelude::*;
 
 use crate::env::{EnvMode, EnvStack};
 use crate::exec::exec_subshell;
-use crate::wcstringutil::split_string;
 use crate::wutil::fish_iswalnum;
 
 const VAR_NAME_PREFIX: &wstr = L!("_flag_");
@@ -158,7 +157,7 @@ fn check_for_mutually_exclusive_flags(
 // information to parse the values associated with any `--exclusive` flags.
 fn parse_exclusive_args(opts: &mut ArgParseCmdOpts, streams: &mut IoStreams) -> Option<c_int> {
     for raw_xflags in &opts.raw_exclusive_flags {
-        let xflags = split_string(raw_xflags, ',');
+        let xflags: Vec<_> = raw_xflags.split(',').collect();
         if xflags.len() < 2 {
             streams.err.append(wgettext_fmt!(
                 "%ls: exclusive flag string '%ls' is not valid\n",
@@ -169,7 +168,7 @@ fn parse_exclusive_args(opts: &mut ArgParseCmdOpts, streams: &mut IoStreams) ->
         }
 
         let exclusive_set: &mut Vec<char> = &mut vec![];
-        for flag in &xflags {
+        for flag in xflags {
             if flag.char_count() == 1 && opts.options.contains_key(&flag.char_at(0)) {
                 let short = flag.char_at(0);
                 // It's a short flag.

src/builtins/string/length.rs

@@ -1,7 +1,5 @@
 use super::*;
 
-use crate::wcstringutil::split_string;
-
 #[derive(Default)]
 pub struct Length {
     quiet: bool,
@@ -36,11 +34,17 @@ impl StringSubCommand<'_> for Length {
         for (arg, _) in arguments(args, optind, streams) {
             if self.visible {
                 // Visible length only makes sense line-wise.
-                for line in split_string(&arg, '\n') {
+                for line in {
+                    let val: &wstr = &arg;
+                    val.split('\n')
+                } {
                     let mut max = 0;
                     // Carriage-return returns us to the beginning. The longest substring without
                     // carriage-return determines the overall width.
-                    for reset in split_string(&line, '\r') {
+                    for reset in {
+                        let val = &line;
+                        val.split('\r')
+                    } {
                         let n = width_without_escapes(&reset, 0);
                         max = usize::max(max, n);
                     }

src/builtins/string/shorten.rs

@@ -1,6 +1,5 @@
 use super::*;
 use crate::common::get_ellipsis_str;
-use crate::wcstringutil::split_string;
 
 pub struct Shorten<'args> {
     ellipsis: &'args wstr,
@@ -92,13 +91,14 @@ impl<'args> StringSubCommand<'args> for Shorten<'args> {
             // Visible width only makes sense line-wise.
             // So either we have no-newlines (which means we shorten on the first newline),
             // or we handle the lines separately.
-            let mut splits = split_string(&arg, '\n').into_iter();
-            if self.no_newline && splits.len() > 1 {
+            let mut splits = arg.split('\n').peekable();
+            if self.no_newline && splits.peek().is_some() {
                 let mut s = match self.shorten_from {
                     Direction::Right => splits.next(),
                     Direction::Left => splits.last(),
                 }
-                .unwrap();
+                .unwrap()
+                .to_owned();
                 s.push_utfstr(&self.ellipsis);
                 let width = width_without_escapes(&s, 0);
 
@@ -112,7 +112,7 @@ impl<'args> StringSubCommand<'args> for Shorten<'args> {
                     if width > 0 && width < min_width {
                         min_width = width;
                     }
-                    inputs.push(s);
+                    inputs.push(s.into());
                 }
             }
         }

src/env_universal_common.rs

@@ -11,7 +11,7 @@ use crate::flog::{FLOG, FLOGF};
 use crate::path::path_get_config;
 use crate::path::{path_get_config_remoteness, DirRemoteness};
 use crate::wchar::{decode_byte_from_char, prelude::*};
-use crate::wcstringutil::{join_strings, split_string, string_suffixes_string, LineIterator};
+use crate::wcstringutil::{join_strings, string_suffixes_string, LineIterator};
 use crate::wutil::{
     file_id_for_fd, file_id_for_path, file_id_for_path_narrow, wdirname, wrealpath, wrename, wstat,
     wunlink, FileId, INVALID_FILE_ID,
@@ -995,7 +995,7 @@ fn decode_serialized(val: &wstr) -> Vec<WString> {
     if val == ENV_NULL {
         return vec![];
     }
-    split_string(val, UVAR_ARRAY_SEP)
+    val.split(UVAR_ARRAY_SEP).map(|v| v.to_owned()).collect()
 }
 
 /// Decode a a list into a serialized universal variable value.

src/wcstringutil.rs

@@ -325,11 +325,6 @@ fn wcs2string_bad_char(c: char) {
     );
 }
 
-/// Split a string by a separator character.
-pub fn split_string(val: &wstr, sep: char) -> Vec<WString> {
-    val.split(sep).map(wstr::to_owned).collect()
-}
-
 /// Split a string by runs of any of the separator characters provided in `seps`.
 /// Note the delimiters are the characters in `seps`, not `seps` itself.
 /// `seps` may contain the NUL character.

src/wutil/mod.rs

@@ -17,7 +17,7 @@ use crate::fds::AutoCloseFd;
 use crate::flog::FLOGF;
 use crate::wchar::{wstr, WString, L};
 use crate::wchar_ext::WExt;
-use crate::wcstringutil::{join_strings, split_string, wcs2string_callback};
+use crate::wcstringutil::{join_strings, wcs2string_callback};
 use errno::errno;
 pub use gettext::{wgettext, wgettext_fmt, wgettext_maybe_fmt, wgettext_str};
 pub use printf::sprintf;
@@ -291,8 +291,8 @@ pub fn path_normalize_for_cd(wd: &wstr, path: &wstr) -> WString {
     }
 
     // Split our strings by the sep.
-    let mut wd_comps = split_string(wd, sep);
-    let path_comps = split_string(path, sep);
+    let mut wd_comps = wd.split(sep).collect::<Vec<_>>();
+    let path_comps = path.split(sep).collect::<Vec<_>>();
 
     // Remove empty segments from wd_comps.
     // In particular this removes the leading and trailing empties.