Escape identifiers contains only underscore

Fix #73

Author: bashor

src/ast/typescript/typeScriptAstUtils.kt

@@ -55,6 +55,7 @@ fun String.escapeIfNeed(): String {
 private fun String.isIdentifier(): Boolean {
     if (isEmpty()) return false
     if (this in SHOULD_BE_ESCAPED) return false
+    if (this.all { it == '_' }) return false
     if (!this[0].isIdentifierStart()) return false
     return this.drop(1).all { it.isIdentifierPart() }
 }

testData/escaping.d.kt

@@ -21,6 +21,7 @@ external open class `is`<`interface`> {
     open fun `package`(a: Any): Boolean = definedExternally
 }
 external fun <T, U> When(value: `when`.Promise<T>, transform: (`val`: T) -> U): `fun`.Promise<U> = definedExternally
+external var `_`: `__`.`___` = definedExternally
 
 // ------------------------------------------------------------------------------------------
 @file:JsQualifier("when")
@@ -29,3 +30,10 @@ package escaping.`when`
 external var `$`: Boolean = definedExternally
 external fun `package`(`as`: bar.string.`interface`, b: `$boo`.`typealias`): `$tring` = definedExternally
 external interface Promise<T>
+
+// ------------------------------------------------------------------------------------------
+@file:JsQualifier("__")
+package escaping.`__`
+
+external interface `___`
+external interface _OK_

testData/escaping.d.ts

@@ -32,5 +32,12 @@ declare namespace when {
     interface Promise<T> {}
 }
 
-// val var is as interface package object when typealias fun in This
-// contains any of: $ \s
+declare var _: __.___;
+
+declare namespace __ {
+    interface ___ {
+    }
+
+    interface _OK_ {
+    }
+}

testData/mergeDeclarations/interfaces.d.kt

@@ -1,5 +1,5 @@
 @file:JsQualifier("_")
-package interfaces._
+package interfaces.`_`
 
 external interface LoDashStatic {
     fun chain(value: Number): LoDashWrapper<Number>

testData/mergeDeclarations/varWith/module.d.kt

@@ -1,23 +1,23 @@
 package module
 
 @JsModule("lodash")
-external val _: _.LoDashStatic = definedExternally
+external val `_`: `_`.LoDashStatic = definedExternally
 
 // ------------------------------------------------------------------------------------------
 @file:JsModule("lodash")
-package module._
+package module.`_`
 
 external interface LoDashStatic {
     @nativeInvoke
     operator fun invoke(value: Number): LoDashWrapper<Number>
     var VERSION: String
-    var support: Support
+    var support: `_`.Support
 }
 external interface Support {
     var argsClass: Boolean
     var argsObject: Boolean
 }
 external interface LoDashArrayWrapper<T> {
-    fun difference(vararg others: Array<T>): LoDashArrayWrapper<T>
-    fun difference(vararg others: List<T>): LoDashArrayWrapper<T>
+    fun difference(vararg others: Array<T>): `_`.LoDashArrayWrapper<T>
+    fun difference(vararg others: List<T>): `_`.LoDashArrayWrapper<T>
 }