feat(prettier): output to stdout instead of write file by default unless specified --write flag

format.ts

@@ -16,7 +16,8 @@ async function main(opts): Promise<void> {
     "--ignore",
     "testdata",
     "--ignore",
-    "vendor"
+    "vendor",
+    "--write"
   ];
 
   if (opts.check) {

prettier/main.ts

@@ -11,7 +11,7 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 // This script formats the given source files. If the files are omitted, it
 // formats the all files in the repository.
-const { args, exit, readFile, writeFile } = Deno;
+const { args, exit, readFile, writeFile, stdout } = Deno;
 import { glob } from "../fs/glob.ts";
 import { walk, WalkInfo } from "../fs/walk.ts";
 import { parse } from "../flags/mod.ts";
@@ -25,6 +25,7 @@ Usage: deno prettier/main.ts [options] [files...]
 Options:
   -H, --help                 Show this help message and exit.
   --check                    Check if the source files are formatted.
+  --write                    Whether to write to the file, otherwise it will output to stdout, Defaults to false.
   --ignore <path>            Ignore the given path(s).
 
 JS/TS Styling Options:
@@ -54,14 +55,17 @@ Markdown Styling Options:
                              Defaults to preserve.
 
 Example:
-  deno prettier/main.ts script1.ts script2.js
+  deno run prettier/main.ts --write script1.ts script2.js
                              Formats the files
 
-  deno prettier/main.ts --check script1.ts script2.js
+  deno run prettier/main.ts --check script1.ts script2.js
                              Checks if the files are formatted
 
-  deno prettier/main.ts
+  deno run prettier/main.ts --write
                              Formats the all files in the repository
+
+  deno run prettier/main.ts script1.ts
+                             Print the formatted code to stdout
 `;
 
 // Available parsers
@@ -78,6 +82,7 @@ interface PrettierOptions {
   arrowParens: string;
   proseWrap: string;
   endOfLine: string;
+  write: boolean;
 }
 
 const encoder = new TextEncoder();
@@ -139,15 +144,20 @@ async function formatFile(
     return;
   }
 
-  const formatted = prettier.format(text, {
+  const formatted: string = prettier.format(text, {
     ...prettierOpts,
     parser,
     plugins: prettierPlugins
   });
 
-  if (text !== formatted) {
-    console.log(`Formatting ${filename}`);
-    await writeFile(filename, encoder.encode(formatted));
+  const fileUnit8 = encoder.encode(formatted);
+  if (prettierOpts.write) {
+    if (text !== formatted) {
+      console.log(`Formatting ${filename}`);
+      await writeFile(filename, fileUnit8);
+    }
+  } else {
+    await stdout.write(fileUnit8);
   }
 }
 
@@ -230,7 +240,8 @@ async function main(opts): Promise<void> {
     bracketSpacing: Boolean(opts["bracket-spacing"]),
     arrowParens: opts["arrow-parens"],
     proseWrap: opts["prose-wrap"],
-    endOfLine: opts["end-of-line"]
+    endOfLine: opts["end-of-line"],
+    write: opts["write"]
   };
 
   if (help) {
@@ -275,7 +286,8 @@ main(
       "semi",
       "use-tabs",
       "single-quote",
-      "bracket-spacing"
+      "bracket-spacing",
+      "write"
     ],
     default: {
       ignore: [],
@@ -288,7 +300,8 @@ main(
       "bracket-spacing": true,
       "arrow-parens": "avoid",
       "prose-wrap": "preserve",
-      "end-of-line": "auto"
+      "end-of-line": "auto",
+      write: false
     },
     alias: {
       H: "help"

prettier/main_test.ts

@@ -1,5 +1,6 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
 import { join } from "../fs/path.ts";
+import { EOL } from "../fs/path/constants.ts";
 import { assertEquals } from "../testing/asserts.ts";
 import { test } from "../testing/mod.ts";
 import { xrun } from "./util.ts";
@@ -59,7 +60,7 @@ test(async function testPrettierCheckAndFormatFiles(): Promise<void> {
   assertEquals(code, 1);
   assertEquals(normalizeOutput(stdout), "Some files are not formatted");
 
-  var { code, stdout } = await run([...cmd, ...files]);
+  var { code, stdout } = await run([...cmd, "--write", ...files]);
   assertEquals(code, 0);
   assertEquals(
     normalizeOutput(stdout),
@@ -83,7 +84,7 @@ test(async function testPrettierCheckAndFormatDirs(): Promise<void> {
   assertEquals(code, 1);
   assertEquals(normalizeOutput(stdout), "Some files are not formatted");
 
-  var { code, stdout } = await run([...cmd, ...dirs]);
+  var { code, stdout } = await run([...cmd, "--write", ...dirs]);
   assertEquals(code, 0);
   assertEquals(
     normalizeOutput(stdout),
@@ -111,15 +112,23 @@ test(async function testPrettierOptions(): Promise<void> {
   const getSourceCode = async (f: string): Promise<string> =>
     decoder.decode(await Deno.readFile(f));
 
-  await run([...cmd, "--no-semi", file0]);
+  await run([...cmd, "--no-semi", "--write", file0]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file0)),
     `console.log(0)
 console.log([function foo() {}, function baz() {}, a => {}])
 `
   );
 
-  await run([...cmd, "--print-width", "30", "--tab-width", "4", file0]);
+  await run([
+    ...cmd,
+    "--print-width",
+    "30",
+    "--tab-width",
+    "4",
+    "--write",
+    file0
+  ]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file0)),
     `console.log(0);
@@ -131,7 +140,7 @@ console.log([
 `
   );
 
-  await run([...cmd, "--print-width", "30", "--use-tabs", file0]);
+  await run([...cmd, "--print-width", "30", "--use-tabs", "--write", file0]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file0)),
     `console.log(0);
@@ -143,14 +152,22 @@ console.log([
 `
   );
 
-  await run([...cmd, "--single-quote", file1]);
+  await run([...cmd, "--single-quote", "--write", file1]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file1)),
     `console.log('1');
 `
   );
 
-  await run([...cmd, "--print-width", "30", "--trailing-comma", "all", file0]);
+  await run([
+    ...cmd,
+    "--print-width",
+    "30",
+    "--trailing-comma",
+    "all",
+    "--write",
+    file0
+  ]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file0)),
     `console.log(0);
@@ -162,31 +179,55 @@ console.log([
 `
   );
 
-  await run([...cmd, "--no-bracket-spacing", file2]);
+  await run([...cmd, "--no-bracket-spacing", "--write", file2]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file2)),
     `console.log({a: 1});
 `
   );
 
-  await run([...cmd, "--arrow-parens", "always", file0]);
+  await run([...cmd, "--arrow-parens", "always", "--write", file0]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file0)),
     `console.log(0);
 console.log([function foo() {}, function baz() {}, (a) => {}]);
 `
   );
 
-  await run([...cmd, "--prose-wrap", "always", file3]);
+  await run([...cmd, "--prose-wrap", "always", "--write", file3]);
   assertEquals(
     normalizeSourceCode(await getSourceCode(file3)),
     `Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor
 incididunt ut labore et dolore magna aliqua.
 `
   );
 
-  await run([...cmd, "--end-of-line", "crlf", file2]);
+  await run([...cmd, "--end-of-line", "crlf", "--write", file2]);
   assertEquals(await getSourceCode(file2), "console.log({ a: 1 });\r\n");
 
   await clearTestdataChanges();
 });
+
+test(async function testPrettierPrintToStdout(): Promise<void> {
+  await clearTestdataChanges();
+
+  const file0 = join(testdata, "0.ts");
+  const file1 = join(testdata, "formatted.ts");
+
+  const getSourceCode = async (f: string): Promise<string> =>
+    decoder.decode(await Deno.readFile(f));
+
+  const { stdout } = await run([...cmd, file0]);
+  // The source file will not change without `--write` flags.
+  assertEquals(await getSourceCode(file0), "console.log (0)" + EOL);
+  // The output should be formatted code.
+  assertEquals(stdout, "console.log(0);" + EOL);
+
+  const { stdout: formattedCode } = await run([...cmd, file1]);
+  // The source file will not change without `--write` flags.
+  assertEquals(await getSourceCode(file1), "console.log(0);" + EOL);
+  // The output will be formatted code even it is the same as the source file's content.
+  assertEquals(formattedCode, "console.log(0);" + EOL);
+
+  await clearTestdataChanges();
+});

prettier/testdata/formatted.ts

@@ -0,0 +1 @@
+console.log(0);