Emit shebangs when printing (#1193)

Author: AlCalzone

internal/printer/printer.go

@@ -4336,7 +4336,11 @@ func (p *Printer) emitJSDocNode(node *ast.Node) {
 //
 
 func (p *Printer) emitShebangIfNeeded(node *ast.SourceFile) {
-	// !!!
+	shebang := scanner.GetShebang(node.Text())
+	if shebang != "" {
+		p.writeComment(shebang)
+		p.writeLine()
+	}
 }
 
 func (p *Printer) emitPrologueDirectives(statements *ast.StatementList) int {

internal/scanner/scanner.go

@@ -2260,6 +2260,15 @@ func scanShebangTrivia(text string, pos int) int {
 	return pos
 }
 
+func GetShebang(text string) string {
+	if !isShebangTrivia(text, 0) {
+		return ""
+	}
+
+	end := scanShebangTrivia(text, 0)
+	return text[:end]
+}
+
 func GetScannerForSourceFile(sourceFile *ast.SourceFile, pos int) *Scanner {
 	s := NewScanner()
 	s.text = sourceFile.Text()

testdata/baselines/reference/submodule/compiler/shebang.js

@@ -6,4 +6,5 @@ var foo = 'I wish the generated JS to be executed in node';
 
 
 //// [shebang.js]
+#!/usr/bin/env node
 var foo = 'I wish the generated JS to be executed in node';

testdata/baselines/reference/submodule/compiler/shebang.js.diff

@@ -15,6 +15,7 @@ import {x} from "test";
 use(x);
 
 //// [f.js]
+#!/usr/bin/env node
 "use strict";
 Object.defineProperty(exports, "__esModule", { value: true });
 /// <reference path="f.d.ts"/>

testdata/baselines/reference/submodule/compiler/shebangBeforeReferences.js

@@ -1,10 +1,8 @@
 --- old.shebangBeforeReferences.js
 +++ new.shebangBeforeReferences.js
-@@= skipped -14, +14 lines =@@
- use(x);
-
+@@= skipped -16, +16 lines =@@
  //// [f.js]
--#!/usr/bin/env node
+ #!/usr/bin/env node
  "use strict";
 -/// <reference path="f.d.ts"/>
  Object.defineProperty(exports, "__esModule", { value: true });