Convert os-release module to typescript

Change-type: patch
Signed-off-by: Cameron Diver <cameron@resin.io>

src/lib/os-release.coffee

@@ -1,34 +0,0 @@
-Promise = require 'bluebird'
-fs = require 'fs'
-_ = require 'lodash'
-
-exports.getOSReleaseField = (path, field) ->
-	try
-		releaseData = fs.readFileSync(path)
-		lines = releaseData.toString().split('\n')
-		releaseItems = {}
-		for line in lines
-			[ key, val ] = line.split('=')
-			releaseItems[_.trim(key)] = _.trim(val)
-		if !releaseItems[field]?
-			throw new Error("Field #{field} not available in #{path}")
-		# Remove enclosing quotes: http://stackoverflow.com/a/19156197/2549019
-		return releaseItems[field].replace(/^"(.+(?="$))"$/, '$1')
-	catch err
-		console.log('Could not get OS release field: ', err.message)
-		return undefined
-
-
-exports.getOSVersionSync = (path) ->
-	exports.getOSReleaseField(path, 'PRETTY_NAME')
-
-exports.getOSVersion = (path) ->
-	Promise.try ->
-		exports.getOSVersionSync(path)
-
-exports.getOSVariantSync = (path) ->
-	exports.getOSReleaseField(path, 'VARIANT_ID')
-
-exports.getOSVariant = (path) ->
-	Promise.try ->
-		exports.getOSVariantSync(path)

src/lib/os-release.ts

@@ -0,0 +1,47 @@
+import * as Bluebird from 'bluebird';
+import * as fs from 'fs';
+import * as _ from 'lodash';
+
+// FIXME: Don't use synchronous file reading and change call sites to support a promise
+function getOSReleaseField(path: string, field: string): string | undefined {
+	try {
+		const releaseData = fs.readFileSync(path, 'utf-8');
+		const lines = releaseData.split('\n');
+		const releaseItems: { [field: string]: string} = { };
+
+		for (const line of lines) {
+			const [ key, value ] = line.split('=');
+			releaseItems[_.trim(key)] = _.trim(value);
+		}
+
+		if (releaseItems[field] == null) {
+			throw new Error(`Field ${field} not available in ${path}`);
+		}
+
+		// Remove enclosing quotes: http://stackoverflow.com/a/19156197/2549019
+		return releaseItems[field].replace(/^"(.+(?="$))"$/, '$1');
+	} catch(err) {
+		console.log('Could not get OS release field: ', err.message);
+		return;
+	}
+}
+
+export function getOSVersionSync(path: string): string | undefined {
+	return getOSReleaseField(path, 'PRETTY_NAME');
+}
+
+export function getOSVersion(path: string): Bluebird<string | undefined> {
+	return Bluebird.try(() => {
+		return getOSVersionSync(path);
+	});
+}
+
+export function getOSVariantSync(path: string): string | undefined {
+	return getOSReleaseField(path, 'VARIANT_ID');
+}
+
+export function getOSVariant(path: string): Bluebird<string | undefined> {
+	return Bluebird.try(() => {
+		return getOSVariantSync(path);
+	});
+}