Patch restore lead trail space bg color (#10351)

```nu
 $env.config.color_config.leading_trailing_space_bg = { bg: 'white' }; [[a b, 'c   ']; ['  1  ' '    2' '3    '] ['  4  ' "hello   \n  world  " ['  1  ' 2 [1 '  2  ' 3]]]] | table --expand
```


![image](https://github.com/nushell/nushell/assets/20165848/01a35042-0e36-4c51-99a9-3011fabb551b)

ref: #2794
close: #10317

note: test are not actually make scenes cause `nu!` strips colors.
(Ideally it would need a flag to not do so)
note: It does does does ... slower down quite a bit rendering... (

PS: Maybe it's better being a flag to `table` rather then a
configuration option?
PS: I am not sure why the logic was removed in a first place

Cargo.lock

@@ -3078,11 +3078,13 @@ dependencies = [
 name = "nu-table"
 version = "0.84.1"
 dependencies = [
+ "fancy-regex",
  "nu-ansi-term",
  "nu-color-config",
  "nu-engine",
  "nu-protocol",
  "nu-utils",
+ "once_cell",
  "tabled",
 ]
 

crates/nu-command/tests/commands/table.rs

@@ -2664,3 +2664,25 @@ fn table_collapse_padding_zero() {
          ╰─┴─┴─╯"
     );
 }
+
+#[test]
+fn table_leading_trailing_space_bg() {
+    let actual = nu!(
+        r#"$env.config.color_config.leading_trailing_space_bg = { bg: 'white' }; [[a b, 'c   ']; ['  1  ' '    2' '3    '] ['  4  ' "hello\nworld" ['  1  ' 2 [1 '  2  ' 3]]]] | table"#
+    );
+    assert_eq!(
+        actual.out,
+        "╭───┬───────┬───────┬────────────────╮│ # │   a   │   b   │      c         │├───┼───────┼───────┼────────────────┤│ 0 │   1   │     2 │ 3              ││ 1 │   4   │ hello │ [list 3 items] ││   │       │ world │                │╰───┴───────┴───────┴────────────────╯"
+    );
+}
+
+#[test]
+fn table_leading_trailing_space_bg_expand() {
+    let actual = nu!(
+        r#"$env.config.color_config.leading_trailing_space_bg = { bg: 'white' }; [[a b, 'c   ']; ['  1  ' '    2' '3    '] ['  4  ' "hello\nworld" ['  1  ' 2 [1 '  2  ' 3]]]] | table --expand"#
+    );
+    assert_eq!(
+        actual.out,
+        "╭───┬───────┬───────┬───────────────────────╮│ # │   a   │   b   │         c             │├───┼───────┼───────┼───────────────────────┤│ 0 │   1   │     2 │ 3                     ││ 1 │   4   │ hello │ ╭───┬───────────────╮ ││   │       │ world │ │ 0 │   1           │ ││   │       │       │ │ 1 │             2 │ ││   │       │       │ │ 2 │ ╭───┬───────╮ │ ││   │       │       │ │   │ │ 0 │     1 │ │ ││   │       │       │ │   │ │ 1 │   2   │ │ ││   │       │       │ │   │ │ 2 │     3 │ │ ││   │       │       │ │   │ ╰───┴───────╯ │ ││   │       │       │ ╰───┴───────────────╯ │╰───┴───────┴───────┴───────────────────────╯"
+    );
+}

crates/nu-table/Cargo.toml

@@ -16,6 +16,8 @@ nu-utils = { path = "../nu-utils", version = "0.84.1" }
 nu-engine = { path = "../nu-engine", version = "0.84.1" }
 nu-color-config = { path = "../nu-color-config", version = "0.84.1" }
 nu-ansi-term = "0.49.0"
+once_cell = "1.18"
+fancy-regex = "0.11"
 tabled = { version = "0.14.0", features = ["color"], default-features = false }
 
 [dev-dependencies]

crates/nu-table/src/common.rs

@@ -62,6 +62,16 @@ pub fn get_index_style(style_computer: &StyleComputer) -> TextStyle {
     )
 }
 
+pub fn get_leading_trailing_space_style(style_computer: &StyleComputer) -> TextStyle {
+    TextStyle::with_style(
+        Alignment::Right,
+        style_computer.compute(
+            "leading_trailing_space_bg",
+            &Value::string("", Span::unknown()),
+        ),
+    )
+}
+
 pub fn get_value_style(value: &Value, config: &Config, style_computer: &StyleComputer) -> NuText {
     match value {
         // Float precision is required here.

crates/nu-table/src/table.rs

@@ -40,6 +40,8 @@ struct Styles {
     index: AnsiColor<'static>,
     header: AnsiColor<'static>,
     data: EntityMap<AnsiColor<'static>>,
+    space_lead: Option<AnsiColor<'static>>,
+    space_trail: Option<AnsiColor<'static>>,
     data_is_set: bool,
 }
 
@@ -137,6 +139,13 @@ impl NuTable {
         self.alignments.data = convert_alignment(style.alignment);
     }
 
+    pub fn set_trail_lead_style(&mut self, head: Style, tail: Style) {
+        let style_head = AnsiColor::from(convert_style(head));
+        let style_tail = AnsiColor::from(convert_style(tail));
+        self.styles.space_trail = Some(style_tail);
+        self.styles.space_lead = Some(style_head);
+    }
+
     pub fn set_indent(&mut self, left: usize, right: usize) {
         self.indent = (left, right);
     }
@@ -225,7 +234,7 @@ fn build_table(
 }
 
 fn draw_table(
-    data: NuRecords,
+    mut data: NuRecords,
     alignments: Alignments,
     styles: Styles,
     widths: Vec<usize>,
@@ -239,6 +248,12 @@ fn draw_table(
     let sep_color = cfg.split_color;
     let border_header = cfg.header_on_border;
 
+    colorize_lead_trail_space(
+        &mut data,
+        styles.space_lead.clone(),
+        styles.space_trail.clone(),
+    );
+
     let data: Vec<Vec<_>> = data.into();
     let mut table = Builder::from(data).build();
 
@@ -908,3 +923,48 @@ fn remove_row(recs: &mut NuRecords, row: usize) -> Vec<String> {
 
     columns
 }
+
+fn colorize_lead_trail_space(
+    data: &mut NuRecords,
+    lead: Option<AnsiColor<'_>>,
+    trail: Option<AnsiColor<'_>>,
+) {
+    use fancy_regex::Captures;
+    use fancy_regex::Regex;
+    use once_cell::sync::Lazy;
+
+    static RE_LEADING: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r"(?m)(?P<beginsp>^\s+)").expect("error with leading space regex"));
+    static RE_TRAILING: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r"(?m)(?P<endsp>\s+$)").expect("error with trailing space regex"));
+
+    if lead.is_none() && trail.is_none() {
+        return;
+    }
+
+    for row in data.iter_mut() {
+        for cell in row {
+            let mut buf = cell.as_ref().to_owned();
+
+            if let Some(color) = &lead {
+                buf = RE_LEADING
+                    .replace_all(cell.as_ref(), |cap: &Captures| {
+                        let spaces = cap.get(1).expect("valid").as_str();
+                        format!("{}{}{}", color.get_prefix(), spaces, color.get_suffix())
+                    })
+                    .into_owned();
+            }
+
+            if let Some(color) = &trail {
+                buf = RE_TRAILING
+                    .replace_all(buf.as_ref(), |cap: &Captures| {
+                        let spaces = cap.get(1).expect("valid").as_str();
+                        format!("{}{}{}", color.get_prefix(), spaces, color.get_suffix())
+                    })
+                    .into_owned();
+            }
+
+            *cell = CellInfo::new(buf);
+        }
+    }
+}

crates/nu-table/src/types/expanded.rs

@@ -9,8 +9,8 @@ use tabled::grid::config::Position;
 use crate::{
     common::{
         create_nu_table_config, error_sign, get_header_style, get_index_style,
-        load_theme_from_config, nu_value_to_string, nu_value_to_string_clean, wrap_text, NuText,
-        StringResult, TableResult, INDEX_COLUMN_NAME,
+        get_leading_trailing_space_style, load_theme_from_config, nu_value_to_string,
+        nu_value_to_string_clean, wrap_text, NuText, StringResult, TableResult, INDEX_COLUMN_NAME,
     },
     string_width, NuTable, NuTableCell, TableOpts, TableOutput,
 };
@@ -178,6 +178,10 @@ fn expanded_table_list(input: &[Value], cfg: Cfg<'_>) -> TableResult {
         table.set_index_style(get_index_style(cfg.opts.style_computer));
         set_data_styles(&mut table, data_styles);
 
+        if let Some(style) = get_leading_trailing_space_style(cfg.opts.style_computer).color_style {
+            table.set_trail_lead_style(style, style);
+        }
+
         return Ok(Some(TableOutput::new(table, false, with_index)));
     }
 
@@ -337,6 +341,10 @@ fn expanded_table_list(input: &[Value], cfg: Cfg<'_>) -> TableResult {
     table.set_indent(cfg.opts.indent.0, cfg.opts.indent.1);
     set_data_styles(&mut table, data_styles);
 
+    if let Some(style) = get_leading_trailing_space_style(cfg.opts.style_computer).color_style {
+        table.set_trail_lead_style(style, style);
+    }
+
     Ok(Some(TableOutput::new(table, true, with_index)))
 }
 
@@ -387,6 +395,10 @@ fn expanded_table_kv(record: &Record, cfg: Cfg<'_>) -> StringResult {
     table.set_index_style(get_key_style(&cfg));
     table.set_indent(cfg.opts.indent.0, cfg.opts.indent.1);
 
+    if let Some(style) = get_leading_trailing_space_style(cfg.opts.style_computer).color_style {
+        table.set_trail_lead_style(style, style);
+    }
+
     let out = TableOutput::new(table, false, true);
 
     maybe_expand_table(out, cfg.opts.width, &cfg.opts)

crates/nu-table/src/types/general.rs

@@ -6,7 +6,7 @@ use crate::{
     clean_charset,
     common::{
         create_nu_table_config, get_empty_style, get_header_style, get_index_style,
-        get_value_style, NuText, INDEX_COLUMN_NAME,
+        get_leading_trailing_space_style, get_value_style, NuText, INDEX_COLUMN_NAME,
     },
     NuTable, NuTableCell, StringResult, TableOpts, TableOutput, TableResult,
 };
@@ -60,6 +60,10 @@ fn kv_table(record: &Record, opts: TableOpts<'_>) -> StringResult {
     let mut table = NuTable::from(data);
     table.set_index_style(TextStyle::default_field());
 
+    if let Some(style) = get_leading_trailing_space_style(opts.style_computer).color_style {
+        table.set_trail_lead_style(style, style);
+    }
+
     let mut out = TableOutput::new(table, false, true);
 
     let left = opts.config.table_indent.left;
@@ -121,6 +125,10 @@ fn to_table_with_header(
     table.set_header_style(get_header_style(opts.style_computer));
     table.set_index_style(get_index_style(opts.style_computer));
 
+    if let Some(style) = get_leading_trailing_space_style(opts.style_computer).color_style {
+        table.set_trail_lead_style(style, style);
+    }
+
     for (i, text) in headers.iter().enumerate() {
         table.insert((0, i), text.to_owned());
     }
@@ -160,6 +168,10 @@ fn to_table_with_no_header(
     let mut table = NuTable::new(input.len(), with_index as usize + 1);
     table.set_index_style(get_index_style(opts.style_computer));
 
+    if let Some(style) = get_leading_trailing_space_style(opts.style_computer).color_style {
+        table.set_trail_lead_style(style, style);
+    }
+
     for (row, item) in input.iter().enumerate() {
         if nu_utils::ctrl_c::was_pressed(&opts.ctrlc) {
             return Ok(None);