Add userHomeDir (denoland/deno_std#521)

Original: https://github.com/denoland/deno_std/commit/ff7fb5a5d696256b232f8435c53087d5b12848ab

3 files changed, 50 insertions, 0 deletions

diff --git a/os/README.md b/os/README.md
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+++ b/os/README.md
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+# os
+
+Module provide platform-independent interface to operating system functionality.
+
+## Usage
+
+### userHomeDir
+
+Returns the current user's home directory. On Unix, including macOS, it returns the \$HOME environment variable. On Windows, it returns %USERPROFILE%.
+Needs permissions to access env (--allow-env).
+
+```ts
+import { userHomeDir } from "https://deno.land/std/os/mod.ts";
+
+userHomeDir();
+```
diff --git a/os/mod.ts b/os/mod.ts
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+++ b/os/mod.ts
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+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+
+/**
+ * Returns the current user's home directory.
+ * On Unix, including macOS, it returns the $HOME environment variable.
+ * On Windows, it returns %USERPROFILE%.
+ * Needs permissions to access env (--allow-env).
+ *
+ * Ported from Go: https://github.com/golang/go/blob/go1.12.5/src/os/file.go#L389
+ */
+export function userHomeDir(): string {
+  let env = "HOME";
+  let envErr = "$HOME";
+
+  if (Deno.platform.os === "win") {
+    env = "USERPROFILE";
+    envErr = "%USERPROFILE%";
+  }
+
+  const value = Deno.env()[env];
+  if (value !== "") {
+    return value;
+  }
+
+  throw new Error(`Environment variable '${envErr}' is not defined.`);
+}
diff --git a/os/test.ts b/os/test.ts
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+++ b/os/test.ts
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+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { test } from "../testing/mod.ts";
+import { assertNotEquals } from "../testing/asserts.ts";
+import { userHomeDir } from "./mod.ts";
+
+test(function testUserHomeDir(): void {
+  assertNotEquals(userHomeDir(), "");
+});