3 files changed, 103 insertions, 10 deletions

diff --git a/std/prettier/ignore.ts b/std/prettier/ignore.ts
new file mode 100644
index 000000000..ffada98de
--- /dev/null
+++ b/std/prettier/ignore.ts
@@ -0,0 +1,15 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+
+/**
+ * Parse the contents of the ignore file and return patterns.
+ * It can parse files like .gitignore/.npmignore/.prettierignore
+ * @param ignoreString
+ * @returns patterns
+ */
+export function parse(ignoreString: string): Set<string> {
+  const partterns = ignoreString
+    .split(/\r?\n/)
+    .filter(line => line.trim() !== "" && line.charAt(0) !== "#");
+
+  return new Set(partterns);
+}
diff --git a/std/prettier/ignore_test.ts b/std/prettier/ignore_test.ts
new file mode 100644
index 000000000..05f67edf4
--- /dev/null
+++ b/std/prettier/ignore_test.ts
@@ -0,0 +1,81 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { test, runIfMain } from "../testing/mod.ts";
+import { assertEquals } from "../testing/asserts.ts";
+import { parse } from "./ignore.ts";
+
+const testCases = [
+  {
+    input: `# this is a comment
+node_modules
+`,
+    output: new Set(["node_modules"])
+  },
+  {
+    input: ` # invalid comment
+`,
+    output: new Set([" # invalid comment"])
+  },
+  {
+    input: `
+node_modules
+package.json
+`,
+    output: new Set(["node_modules", "package.json"])
+  },
+  {
+    input: `
+    node_modules
+    package.json
+`,
+    output: new Set(["    node_modules", "    package.json"])
+  },
+  {
+    input: `*.orig
+*.pyc
+*.swp
+
+/.idea/
+/.vscode/
+gclient_config.py_entries
+/gh-pages/
+/target/
+
+# Files that help ensure VSCode can work but we don't want checked into the
+# repo
+/node_modules
+/tsconfig.json
+
+# We use something stronger than lockfiles, we have all NPM modules stored in a
+# git. We do not download from NPM during build.
+# https://github.com/denoland/deno_third_party
+yarn.lock
+# yarn creates this in error.
+tools/node_modules/
+    `,
+    output: new Set([
+      "*.orig",
+      "*.pyc",
+      "*.swp",
+      "/.idea/",
+      "/.vscode/",
+      "gclient_config.py_entries",
+      "/gh-pages/",
+      "/target/",
+      "/node_modules",
+      "/tsconfig.json",
+      "yarn.lock",
+      "tools/node_modules/"
+    ])
+  }
+];
+
+test({
+  name: "[encoding.ignore] basic",
+  fn(): void {
+    for (const { input, output } of testCases) {
+      assertEquals(parse(input), output);
+    }
+  }
+});
+
+runIfMain(import.meta);
diff --git a/std/prettier/main.ts b/std/prettier/main.ts
index e3f2270c3..b3c469659 100755
--- a/std/prettier/main.ts
+++ b/std/prettier/main.ts
@@ -27,6 +27,7 @@ import { parse } from "../flags/mod.ts";
 import * as path from "../path/mod.ts";
 import * as toml from "../encoding/toml.ts";
 import * as yaml from "../encoding/yaml.ts";
+import * as ignore from "./ignore.ts";
 import { ExpandGlobOptions, WalkInfo, expandGlob } from "../fs/mod.ts";
 import { prettier, prettierPlugins } from "./prettier.ts";
 const { args, cwd, exit, readAll, readFile, stdin, stdout, writeFile } = Deno;
@@ -460,7 +461,7 @@ async function resolveConfig(
 /**
  * auto detect .prettierignore and return pattern if file exist.
  */
-async function autoResolveIgnoreFile(): Promise<string[]> {
+async function autoResolveIgnoreFile(): Promise<Set<string>> {
   const files = await Deno.readDir(".");
 
   for (const f of files) {
@@ -469,20 +470,16 @@ async function autoResolveIgnoreFile(): Promise<string[]> {
     }
   }
 
-  return [];
+  return new Set([]);
 }
 
 /**
  * parse prettier ignore file.
  * @param filepath the ignore file path.
  */
-async function resolveIgnoreFile(filepath: string): Promise<string[]> {
+async function resolveIgnoreFile(filepath: string): Promise<Set<string>> {
   const raw = new TextDecoder().decode(await Deno.readFile(filepath));
-
-  return raw
-    .split("\n")
-    .filter((v: string) => !!v.trim() && v.trim().indexOf("#") !== 0)
-    .map(v => v);
+  return ignore.parse(raw);
 }
 
 async function main(opts): Promise<void> {
@@ -532,12 +529,12 @@ async function main(opts): Promise<void> {
   const ignoreFilepath = opts["ignore-path"];
 
   if (ignoreFilepath && ignoreFilepath !== "disable") {
-    const ignorePatterns: string[] =
+    const ignorePatterns =
       ignoreFilepath === "auto"
         ? await autoResolveIgnoreFile()
         : await resolveIgnoreFile(ignoreFilepath);
 
-    ignore = ignore.concat(ignorePatterns);
+    ignore = ignore.concat(Array.from(ignorePatterns));
   }
 
   const files = getTargetFiles(args.length ? args : ["."], ignore);