feat(compartment-mapper): Add subpath match and replace utility

Author: kriskowal

packages/compartment-mapper/package.json

@@ -57,6 +57,7 @@
   "dependencies": {
     "@endo/cjs-module-analyzer": "workspace:^",
     "@endo/module-source": "workspace:^",
+    "@endo/regexp-escape": "workspace:^",
     "@endo/trampoline": "workspace:^",
     "@endo/zip": "workspace:^",
     "ses": "workspace:^"

packages/compartment-mapper/src/subpath.js

@@ -0,0 +1,27 @@
+import { escapeRegExp } from '@endo/regexp-escape';
+
+/**
+ * @param {string} pattern a subpath pattern of asterisk-delimited literals
+ * @param {string} pattern of respective replacements delimited by asterisks
+ */
+export const makeSubpathReplacer = (pattern, replacement) => {
+  const patternParts = pattern.split('*');
+  const replacementParts = replacement.split('*');
+  const re = new RegExp(`^${patternParts.map(escapeRegExp).join('(.*)')}$`);
+  return path => {
+    if (patternParts.length !== replacementParts.length) {
+      return null;
+    }
+    const match = re.exec(path);
+    if (match === null) {
+      return null;
+    }
+    let reconstruction = '';
+    let i;
+    for (i = 0; i < replacementParts.length - 1; i++) {
+      reconstruction += replacementParts[i] + match[i + 1];
+    }
+    reconstruction += replacementParts[i];
+    return reconstruction;
+  };
+};

packages/compartment-mapper/test/subpath.test.js

@@ -0,0 +1,36 @@
+import test from 'ava';
+import { makeSubpathReplacer } from '../src/subpath.js';
+
+test('no wildcard subpath replacement', t => {
+  const replaceSubpath = makeSubpathReplacer('a/b/c', 'x/y/z');
+  t.is(replaceSubpath(''), null);
+  t.is(replaceSubpath('a'), null);
+  t.is(replaceSubpath('a/b'), null);
+  t.is(replaceSubpath('a/b/c'), 'x/y/z');
+  t.is(replaceSubpath('a/b/c/d'), null);
+});
+
+test('single wildcard subpath replacement', t => {
+  const replaceSubpath = makeSubpathReplacer('a/*/c', 'x/*/z');
+  t.is(replaceSubpath(''), null);
+  t.is(replaceSubpath('a'), null);
+  t.is(replaceSubpath('a/b'), null);
+  t.is(replaceSubpath('a/*/c'), 'x/*/z');
+  t.is(replaceSubpath('a/b/c'), 'x/b/z');
+  t.is(replaceSubpath('a/1/2/c'), 'x/1/2/z');
+});
+
+test('double wildcard subpath replacement', t => {
+  const replaceSubpath = makeSubpathReplacer('a/*/b/*/c', 'x/*/y/*/z');
+  t.is(replaceSubpath('a/1/2/b/3/4/c'), 'x/1/2/y/3/4/z');
+});
+
+test('double wildcard subpath replacement without slashes', t => {
+  const replaceSubpath = makeSubpathReplacer('a*b*c', 'x*y*z');
+  t.is(replaceSubpath('a12b34c'), 'x12y34z');
+});
+
+test('mismatched subpath', t => {
+  const replaceSubpath = makeSubpathReplacer('*-*', '*');
+  t.is(replaceSubpath('1-2'), null);
+});