feat(es/codegen): Add to_code (#8968)

**Description:**

This is a utility function for printing an AST node as a string

crates/swc_ecma_codegen/src/lib.rs

@@ -13,7 +13,7 @@ use swc_atoms::Atom;
 use swc_common::{
     comments::{CommentKind, Comments},
     sync::Lrc,
-    BytePos, SourceMapper, Span, Spanned, DUMMY_SP,
+    BytePos, SourceMap, SourceMapper, Span, Spanned, DUMMY_SP,
 };
 use swc_ecma_ast::*;
 use swc_ecma_codegen_macros::emitter;
@@ -38,6 +38,36 @@ pub mod util;
 
 pub type Result = io::Result<()>;
 
+/// Generate a code from a syntax node using default options.
+pub fn to_code_default(
+    cm: Lrc<SourceMap>,
+    comments: Option<&dyn Comments>,
+    node: impl Node,
+) -> String {
+    let mut buf = vec![];
+    {
+        let mut emitter = Emitter {
+            cfg: Default::default(),
+            cm: cm.clone(),
+            comments,
+            wr: text_writer::JsWriter::new(cm, "\n", &mut buf, None),
+        };
+        node.emit_with(&mut emitter).unwrap();
+    }
+
+    String::from_utf8(buf).expect("codegen generated non-utf8 output")
+}
+
+/// Generate a code from a syntax node using default options.
+pub fn to_code_with_comments(comments: Option<&dyn Comments>, node: impl Node) -> String {
+    to_code_default(Default::default(), comments, node)
+}
+
+/// Generate a code from a syntax node using default options.
+pub fn to_code(node: impl Node) -> String {
+    to_code_with_comments(None, node)
+}
+
 pub trait Node: Spanned {
     fn emit_with<W, S>(&self, e: &mut Emitter<'_, W, S>) -> Result
     where

crates/swc_ecma_transforms_testing/src/lib.rs

@@ -28,7 +28,7 @@ use swc_common::{
     FileName, Mark, SourceMap, DUMMY_SP,
 };
 use swc_ecma_ast::*;
-use swc_ecma_codegen::Emitter;
+use swc_ecma_codegen::{to_code_default, Emitter};
 use swc_ecma_parser::{lexer::Lexer, Parser, StringInput, Syntax};
 use swc_ecma_testing::{exec_node_js, JsExecOptions};
 use swc_ecma_transforms_base::{
@@ -188,26 +188,7 @@ impl<'a> Tester<'a> {
     }
 
     pub fn print(&mut self, module: &Module, comments: &Rc<SingleThreadedComments>) -> String {
-        let mut buf = vec![];
-        {
-            let mut emitter = Emitter {
-                cfg: Default::default(),
-                cm: self.cm.clone(),
-                wr: Box::new(swc_ecma_codegen::text_writer::JsWriter::new(
-                    self.cm.clone(),
-                    "\n",
-                    &mut buf,
-                    None,
-                )),
-                comments: Some(comments),
-            };
-
-            // println!("Emitting: {:?}", module);
-            emitter.emit_module(module).unwrap();
-        }
-
-        let s = String::from_utf8_lossy(&buf);
-        s.to_string()
+        to_code_default(self.cm.clone(), Some(comments), module)
     }
 }
 

crates/swc_ecma_transforms_typescript/examples/ts_to_js.rs

@@ -10,7 +10,7 @@ use swc_common::{
     sync::Lrc,
     Globals, Mark, SourceMap, GLOBALS,
 };
-use swc_ecma_codegen::{text_writer::JsWriter, Emitter};
+use swc_ecma_codegen::to_code_default;
 use swc_ecma_parser::{lexer::Lexer, Parser, StringInput, Syntax, TsConfig};
 use swc_ecma_transforms_base::{fixer::fixer, hygiene::hygiene, resolver};
 use swc_ecma_transforms_typescript::strip;
@@ -76,18 +76,6 @@ fn main() {
         // Ensure that we have enough parenthesis.
         let program = module.fold_with(&mut fixer(Some(&comments)));
 
-        let mut buf = vec![];
-        {
-            let mut emitter = Emitter {
-                cfg: swc_ecma_codegen::Config::default(),
-                cm: cm.clone(),
-                comments: Some(&comments),
-                wr: JsWriter::new(cm.clone(), "\n", &mut buf, None),
-            };
-
-            emitter.emit_program(&program).unwrap();
-        }
-
-        println!("{}", String::from_utf8(buf).expect("non-utf8?"));
+        println!("{}", to_code_default(cm, Some(&comments), program));
     })
 }

crates/swc_ecma_transforms_typescript/tests/strip_correctness.rs

@@ -1,12 +1,8 @@
-use std::{
-    io::{self, Write},
-    path::PathBuf,
-    sync::{Arc, RwLock},
-};
+use std::path::PathBuf;
 
 use swc_common::{FileName, Mark};
 use swc_ecma_ast::*;
-use swc_ecma_codegen::Emitter;
+use swc_ecma_codegen::to_code_default;
 use swc_ecma_parser::{lexer::Lexer, EsConfig, Parser, Syntax, TsConfig};
 use swc_ecma_transforms_base::{fixer::fixer, hygiene::hygiene, resolver};
 use swc_ecma_transforms_typescript::typescript;
@@ -98,21 +94,7 @@ fn identity(entry: PathBuf) {
             None,
         );
 
-        let mut wr = Buf(Arc::new(RwLock::new(vec![])));
-
-        {
-            let mut emitter = Emitter {
-                cfg: swc_ecma_codegen::Config::default(),
-                cm: cm.clone(),
-                wr: Box::new(swc_ecma_codegen::text_writer::JsWriter::new(
-                    cm.clone(),
-                    "\n",
-                    &mut wr,
-                    None,
-                )),
-                comments: None,
-            };
-
+        let js_content = {
             // Parse source
             let program = parser
                 .parse_typescript_module()
@@ -142,10 +124,8 @@ fn identity(entry: PathBuf) {
                 Err(_) => return Ok(()),
             };
 
-            emitter.emit_program(&program).unwrap();
-        }
-
-        let js_content = String::from_utf8_lossy(&wr.0.read().unwrap()).to_string();
+            to_code_default(cm.clone(), None, program)
+        };
 
         println!("---------------- JS ----------------\n\n{}", js_content);
 
@@ -182,15 +162,3 @@ fn identity(entry: PathBuf) {
     })
     .expect("failed to run test");
 }
-
-#[derive(Debug, Clone)]
-struct Buf(Arc<RwLock<Vec<u8>>>);
-impl Write for Buf {
-    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
-        self.0.write().unwrap().write(data)
-    }
-
-    fn flush(&mut self) -> io::Result<()> {
-        self.0.write().unwrap().flush()
-    }
-}