Allow fixed formatter to keep space at line start

src/format/fixed.rs

@@ -105,6 +105,8 @@ pub struct FixedFormatter {
     jieba: Option<Jieba>,
     #[cfg(not(feature = "jieba"))]
     jieba: Option<()>,
+    /// Do not remove space at the start of the line
+    no_remove_space_at_line_start: bool,
     #[allow(unused)]
     typ: Option<ScriptType>,
 }
@@ -118,6 +120,7 @@ impl FixedFormatter {
         break_with_sentence: bool,
         #[cfg(feature = "jieba")] break_chinese_words: bool,
         #[cfg(feature = "jieba")] jieba_dict: Option<String>,
+        no_remove_space_at_line_start: bool,
         typ: Option<ScriptType>,
     ) -> Result<Self> {
         #[cfg(feature = "jieba")]
@@ -142,6 +145,7 @@ impl FixedFormatter {
             jieba,
             #[cfg(not(feature = "jieba"))]
             jieba: None,
+            no_remove_space_at_line_start,
             typ,
         })
     }
@@ -156,6 +160,7 @@ impl FixedFormatter {
             break_with_sentence: false,
             jieba: None,
             typ: None,
+            no_remove_space_at_line_start: false,
         }
     }
 
@@ -202,6 +207,12 @@ impl FixedFormatter {
         self
     }
 
+    #[cfg(test)]
+    fn no_remove_space_at_line_start(mut self, no_remove: bool) -> Self {
+        self.no_remove_space_at_line_start = no_remove;
+        self
+    }
+
     #[cfg(test)]
     #[allow(dead_code)]
     fn typ(mut self, typ: Option<ScriptType>) -> Self {
@@ -566,7 +577,10 @@ impl FixedFormatter {
                 }
             }
 
-            if (current_length == 0 || pre_is_lf) && SPACE_STR_LIST.contains(&grapheme) {
+            if !self.no_remove_space_at_line_start
+                && (current_length == 0 || pre_is_lf)
+                && SPACE_STR_LIST.contains(&grapheme)
+            {
                 i += 1;
                 continue;
             }
@@ -729,6 +743,15 @@ fn test_format() {
         "（This） 「is\n\u{3000}a test."
     );
 
+    let formatter3b = FixedFormatter::builder(10)
+        .break_words(false)
+        .no_remove_space_at_line_start(true);
+
+    assert_eq!(
+        formatter3b.format("（This） 「is a test."),
+        "（This） 「is\n a test."
+    );
+
     let formatter4 = FixedFormatter::builder(10)
         .break_words(false)
         .break_with_sentence(true);

src/format/mod.rs

@@ -17,6 +17,7 @@ pub fn fmt_message(mes: &mut Vec<Message>, opt: FormatOptions, typ: ScriptType)
             break_chinese_words,
             #[cfg(feature = "jieba")]
             jieba_dict,
+            no_remove_space_at_line_start,
         } => {
             let formatter = fixed::FixedFormatter::new(
                 length,
@@ -28,6 +29,7 @@ pub fn fmt_message(mes: &mut Vec<Message>, opt: FormatOptions, typ: ScriptType)
                 break_chinese_words,
                 #[cfg(feature = "jieba")]
                 jieba_dict,
+                no_remove_space_at_line_start,
                 Some(typ),
             )?;
             for message in mes.iter_mut() {