Use browser relative path algorithm for chunks

browser/path.ts

@@ -37,16 +37,17 @@ export function relative(from: string, to: string) {
 	const fromParts = from.split(/[/\\]/).filter(Boolean);
 	const toParts = to.split(/[/\\]/).filter(Boolean);
 
+	if (fromParts[0] === '.') fromParts.shift();
+	if (toParts[0] === '.') toParts.shift();
+
 	while (fromParts[0] && toParts[0] && fromParts[0] === toParts[0]) {
 		fromParts.shift();
 		toParts.shift();
 	}
 
-	while (toParts[0] === '.' || toParts[0] === '..') {
-		const toPart = toParts.shift();
-		if (toPart === '..') {
-			fromParts.pop();
-		}
+	while (toParts[0] === '..' && fromParts.length > 0) {
+		toParts.shift();
+		fromParts.pop();
 	}
 
 	while (fromParts.pop()) {

src/Chunk.ts

@@ -1,5 +1,6 @@
 import sha256 from 'hash.js/lib/hash/sha/256';
 import MagicString, { Bundle as MagicStringBundle, SourceMap } from 'magic-string';
+import { relative } from '../browser/path';
 import ExportDefaultDeclaration from './ast/nodes/ExportDefaultDeclaration';
 import FunctionDeclaration from './ast/nodes/FunctionDeclaration';
 import { UNDEFINED_EXPRESSION } from './ast/values';
@@ -28,7 +29,7 @@ import { error } from './utils/error';
 import { sortByExecutionOrder } from './utils/executionOrder';
 import getIndentString from './utils/getIndentString';
 import { makeLegal } from './utils/identifierHelpers';
-import { basename, dirname, isAbsolute, normalize, relative, resolve } from './utils/path';
+import { basename, dirname, isAbsolute, normalize, resolve } from './utils/path';
 import relativeId, { getAliasName } from './utils/relativeId';
 import renderChunk from './utils/renderChunk';
 import { RenderOptions } from './utils/renderHelpers';

test/function/index.js

@@ -51,6 +51,7 @@ runTestSuiteWithSamples('function', path.resolve(__dirname, 'samples'), (dir, co
 		path.basename(dir) + ': ' + config.description,
 		() => {
 			if (config.show) console.group(path.basename(dir));
+			if (config.before) config.before();
 
 			process.chdir(dir);
 			const warnings = [];

test/function/samples/relative-outside-external/_config.js

@@ -0,0 +1,23 @@
+const assert = require('assert');
+const cwd = process.cwd;
+
+module.exports = {
+	description: 'correctly resolves relative external imports from outside directories',
+	options: {
+		external() {
+			return true;
+		}
+	},
+	before() {
+		process.cwd = () => '/';
+	},
+	context: {
+		require(id) {
+			return id;
+		}
+	},
+	exports(exports) {
+		process.cwd = cwd;
+		assert.strictEqual(exports.value, '../../../test.js');
+	}
+};

test/function/samples/relative-outside-external/main.js

@@ -0,0 +1 @@
+export {default as value} from '../../../test.js';