feat(es/codegen): Add ability to set indentation string via rust api (#…

…7494)

**Description:**

This adds the ability to set the indentation string of JsWriter via the Rust API. The motivation behind this change is to allow people to use other indentations in the emit output like tabs or two spaces via the Rust API.

crates/swc_ecma_codegen/src/text_writer/basic_impl.rs

@@ -13,6 +13,7 @@ use super::{Result, WriteJs};
 /// https://github.com/Microsoft/TypeScript/blob/45eaf42006/src/compiler/utilities.ts#L2548
 pub struct JsWriter<'a, W: Write> {
     indent: usize,
+    indent_str: &'static str,
     line_start: bool,
     line_count: usize,
     line_pos: usize,
@@ -33,6 +34,7 @@ impl<'a, W: Write> JsWriter<'a, W> {
     ) -> Self {
         JsWriter {
             indent: Default::default(),
+            indent_str: "    ",
             line_start: true,
             line_count: 0,
             line_pos: Default::default(),
@@ -44,15 +46,18 @@ impl<'a, W: Write> JsWriter<'a, W> {
         }
     }
 
+    /// Sets the indentation string. Defaults to four spaces.
+    pub fn set_indent_str(&mut self, indent_str: &'static str) {
+        self.indent_str = indent_str;
+    }
+
     #[inline]
     fn write_indent_string(&mut self) -> Result {
-        const INDENT: &str = "    ";
-
         for _ in 0..self.indent {
-            self.raw_write(INDENT)?;
+            self.raw_write(self.indent_str)?;
         }
         if self.srcmap.is_some() {
-            self.line_pos += INDENT.len() * self.indent;
+            self.line_pos += self.indent_str.len() * self.indent;
         }
 
         Ok(())
@@ -324,3 +329,26 @@ fn compute_line_starts(s: &str) -> LineStart {
         byte_pos: line_start,
     }
 }
+
+#[cfg(test)]
+mod test {
+    use std::sync::Arc;
+
+    use swc_common::SourceMap;
+
+    use super::JsWriter;
+    use crate::text_writer::WriteJs;
+
+    #[test]
+    fn changes_indent_str() {
+        let source_map = Arc::new(SourceMap::default());
+        let mut output = Vec::new();
+        let mut writer = JsWriter::new(source_map, "\n", &mut output, None);
+        writer.set_indent_str("\t");
+        writer.increase_indent().unwrap();
+        writer.write_indent_string().unwrap();
+        writer.increase_indent().unwrap();
+        writer.write_indent_string().unwrap();
+        assert_eq!(output, "\t\t\t".as_bytes());
+    }
+}