Added EOL detect / format

fs/eol.ts

@@ -0,0 +1,42 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+
+/** EndOfLine character enum */
+export enum EOL {
+  LF = "\n",
+  CRLF = "\r\n"
+}
+
+const regDetect = /(?:\r?\n)/g;
+const regCRLF = /\r\n/g;
+const regLF = /\n/g;
+
+/**
+ * Detect the EOL character for string input.
+ * returns null if no newline
+ */
+export function detect(content: string): EOL | null {
+  const d = content.match(regDetect);
+  if (!d || d.length === 0) {
+    return null;
+  }
+  const crlf = d.filter(x => x === EOL.CRLF);
+  if (crlf.length > 0) {
+    return EOL.CRLF;
+  } else {
+    return EOL.LF;
+  }
+}
+
+/** Format the file to the targeted EOL */
+export function format(content: string, eol: EOL): string {
+  const _eol = detect(content);
+  if (_eol === eol) {
+    return content;
+  } else {
+    if (_eol === EOL.CRLF) {
+      return content.replace(regCRLF, eol);
+    } else {
+      return content.replace(regLF, eol);
+    }
+  }
+}

fs/eol_test.ts

@@ -0,0 +1,25 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { test } from "../testing/mod.ts";
+import { assertEquals } from "../testing/asserts.ts";
+import { format, detect, EOL } from "./eol.ts";
+
+test(function detectCRLF() {
+  const input = "deno\r\nis not\r\nnode";
+  assertEquals(detect(input), EOL.CRLF);
+});
+test(function detectLF() {
+  const input = "deno\nis not\nnode";
+  assertEquals(detect(input), EOL.LF);
+});
+test(function detectNoNewLine() {
+  const input = "deno is not node";
+  assertEquals(detect(input), null);
+});
+test(function testFormat() {
+  const CRLFinput = "deno\r\nis not\r\nnode";
+  const LFinput = "deno\nis not\nnode";
+  assertEquals(format(CRLFinput, EOL.LF), LFinput);
+  assertEquals(format(LFinput, EOL.LF), LFinput);
+  assertEquals(format(LFinput, EOL.CRLF), CRLFinput);
+  assertEquals(format(CRLFinput, EOL.CRLF), CRLFinput);
+});