change interface to use { resolver } rather than { resolvers }

src/esmockArgs.js

@@ -1,3 +1,5 @@
+import resolver from 'resolvewithplus'
+
 // extracts path or fileurl from stack,
 // '  at <anonymous> (/root/test.js:11:31)' -> /root/test.js
 // '  at Object.handler (file:///D:/a/test.js:11:31)' -> file:///D:/a/test.js
@@ -17,7 +19,7 @@ export default (arg, optsextra) => {
     (new Error).stack.split('\n')[3].replace(stackpathre, '$2'),
     ...arg.slice(1)
   ]
-  arg[4] = {...arg[4], ...optsextra}
+  arg[4] = { resolver, ...arg[4], ...optsextra}
 
   return arg
 }

src/esmockModule.js

@@ -108,23 +108,14 @@ const esmockModuleCreate = async (treeid, def, id, fileURL, opt) => {
   return mockModuleKey
 }
 
-const esmockCustomResolvers = (id, parent, resolvers) => {
-  if (!Array.isArray(resolvers) || !resolvers.length)
-    return null
-
-  return resolvers[0](id, parent)
-    || esmockCustomResolvers(id, parent, resolvers.slice(1))
-}
-
 const esmockModuleId = async (parent, treeid, defs, ids, opt, mocks, id) => {
   ids = ids || Object.keys(defs)
   id = ids[0]
   mocks = mocks || []
 
   if (!id) return mocks
 
-  const fileURL = esmockCustomResolvers(id, parent, opt.resolvers)
-    || resolvewith(id, parent)
+  const fileURL = opt.resolver(id, parent)
   if (!fileURL && opt.isModuleNotFoundError !== false && id !== 'import')
     throw esmockErr.errModuleIdNotFound(id, parent)
 
@@ -134,8 +125,7 @@ const esmockModuleId = async (parent, treeid, defs, ids, opt, mocks, id) => {
 }
 
 const esmockModule = async (moduleId, parent, defs, gdefs, opt) => {
-  const moduleFileURL = esmockCustomResolvers(moduleId, parent, opt.resolvers)
-    || resolvewith(moduleId, parent)
+  const moduleFileURL = opt.resolver(moduleId, parent)
   if (!moduleFileURL)
     throw esmockErr.errModuleIdNotFound(moduleId, parent)
 

tests/tests-node/esmock.node.resolver-custom.test.js

@@ -4,8 +4,19 @@ import module from 'node:module'
 import esmock from 'esmock'
 
 function resolverCustom (moduleId, parent) {
-  return /RESOLVECUSTOM$/.test(moduleId) && parent
-    .replace(/\/tests\/.*$/, '/tests/local/customResolverChild.js')
+  parent = parent.replace(/\/tests\/.*$/, '/tests/tests-node/')
+
+  // This logic looks unusual because of constraints here. This function must:
+  //  * must work at windows, where path.join and path.resolve cause issues
+  //  * must be string-serializable, no external funcions
+  //  * must resolve these moduleIds to corresponding, existing filepaths
+  //    * '../local/customResolverParent.js',
+  //    * 'RESOLVECUSTOM/
+  return (
+    /RESOLVECUSTOM$/.test(moduleId)
+      ? parent + '../local/customResolverChild.js'
+      : parent + moduleId
+  ).replace(/\/tests-node\/\.\./, '')
 }
 
 async function resolve (specifier, context, next) {
@@ -29,7 +40,7 @@ test('should use custom resolver', async () => {
     '../local/customResolverParent.js', {}, {
       RESOLVECUSTOM: ({ isMocked: true })
     }, {
-      resolvers: [resolverCustom]
+      resolver: resolverCustom
     })
 
   assert.ok(customResolverParent.child.isCustomResolverChild)