chore: add omit utility

This change should have no impact on functionality.

This replaces the following pattern:

```javascript
// eslint-disable-next-line no-unused-vars
const { foo, bar, ...rest } = obj
return rest
```

With a new `omit` utility, which I think is clearer:

```javascript
return omit(obj, ['foo', 'bar'])
```

I think this is a useful change on its own, but also makes an upcoming
change slightly easier because I wanted this function.

src/config-import.js

@@ -516,7 +516,6 @@ function parseIcon(filename, buf) {
   if (!matches) {
     throw new Error(`Unexpected icon filename ${filename}`)
   }
-  /* eslint-disable no-unused-vars */
   const [_, name, size, pixelDensityStr] = matches
   const pixelDensity = Number(pixelDensityStr)
   if (!(pixelDensity === 1 || pixelDensity === 2 || pixelDensity === 3)) {

src/core-ownership.js

@@ -15,6 +15,7 @@ import { discoveryKey } from 'hypercore-crypto'
 import pDefer from 'p-defer'
 import { NAMESPACES } from './constants.js'
 import { TypedEmitter } from 'tiny-typed-emitter'
+import { omit } from './lib/omit.js'
 /**
  * @import {
  *   CoreOwnershipWithSignatures,
@@ -167,8 +168,10 @@ export function mapAndValidateCoreOwnership(doc, { coreDiscoveryKey }) {
   if (!verifyCoreOwnership(doc)) {
     throw new Error('Invalid coreOwnership record: signatures are invalid')
   }
-  // eslint-disable-next-line no-unused-vars
-  const { identitySignature, coreSignatures, ...docWithoutSignatures } = doc
+  const docWithoutSignatures = omit(doc, [
+    'identitySignature',
+    'coreSignatures',
+  ])
   docWithoutSignatures.links = []
   return docWithoutSignatures
 }

src/lib/omit.js

@@ -0,0 +1,28 @@
+/**
+ * Returns a new object with the own enumerable keys of `obj` that are not in `keys`.
+ *
+ * In other words, remove some keys from an object.
+ *
+ * @template {object} T
+ * @template {keyof T} K
+ * @param {T} obj
+ * @param {ReadonlyArray<K>} keys
+ * @returns {Omit<T, K>}
+ * @example
+ * const obj = { foo: 1, bar: 2, baz: 3 }
+ * omit(obj, ['foo', 'bar'])
+ * // => { baz: 3 }
+ */
+export function omit(obj, keys) {
+  /** @type {Partial<T>} */ const result = {}
+
+  /** @type {Set<unknown>} */ const toOmit = new Set(keys)
+
+  for (const key in obj) {
+    if (!Object.hasOwn(obj, key)) continue
+    if (toOmit.has(key)) continue
+    result[key] = obj[key]
+  }
+
+  return /** @type {Omit<T, K>} */ (result)
+}

src/mapeo-manager.js

@@ -34,6 +34,7 @@ import {
   projectKeyToPublicId,
 } from './utils.js'
 import { openedNoiseSecretStream } from './lib/noise-secret-stream-helpers.js'
+import { omit } from './lib/omit.js'
 import { RandomAccessFilePool } from './core-manager/random-access-file-pool.js'
 import BlobServerPlugin from './fastify-plugins/blobs.js'
 import IconServerPlugin from './fastify-plugins/icons.js'
@@ -442,9 +443,10 @@ export class MapeoManager extends TypedEmitter {
 
     // 7. Load config, if relevant
     // TODO: see how to expose warnings to frontend
-    /* eslint-disable no-unused-vars */
+    // eslint-disable-next-line no-unused-vars
     let warnings
     if (configPath) {
+      // eslint-disable-next-line no-unused-vars
       warnings = await project.importConfig({ configPath })
     }
 
@@ -917,15 +919,8 @@ export class MapeoManager extends TypedEmitter {
  * @returns {PublicPeerInfo[]}
  */
 function omitPeerProtomux(peers) {
-  return peers.map(
-    ({
-      // @ts-ignore
-      // eslint-disable-next-line no-unused-vars
-      protomux,
-      ...publicPeerInfo
-    }) => {
-      return publicPeerInfo
-    }
+  return peers.map((peer) =>
+    'protomux' in peer ? omit(peer, ['protomux']) : peer
   )
 }
 

src/mapeo-project.js

@@ -43,6 +43,7 @@ import {
   projectKeyToPublicId,
   valueOf,
 } from './utils.js'
+import { omit } from './lib/omit.js'
 import { MemberApi } from './member-api.js'
 import { SyncApi, kHandleDiscoveryKey } from './sync/sync-api.js'
 import { Logger } from './logger.js'
@@ -887,9 +888,7 @@ export class MapeoProject extends TypedEmitter {
  * @returns {EditableProjectSettings}
  */
 function extractEditableProjectSettings(projectDoc) {
-  // eslint-disable-next-line no-unused-vars
-  const { schemaName, ...result } = valueOf(projectDoc)
-  return result
+  return omit(valueOf(projectDoc), ['schemaName'])
 }
 
 /**

src/translation-api.js

@@ -2,6 +2,7 @@ import { and, sql } from 'drizzle-orm'
 import { kCreateWithDocId, kSelect } from './datatype/index.js'
 import { hashObject } from './utils.js'
 import { NotFoundError } from './errors.js'
+import { omit } from './lib/omit.js'
 /** @import { Translation, TranslationValue } from '@comapeo/schema' */
 /** @import { SetOptional } from 'type-fest' */
 
@@ -47,8 +48,7 @@ export default class TranslationApi {
    * @param {TranslationValue} value
    */
   async put(value) {
-    /* eslint-disable no-unused-vars */
-    const { message, ...identifiers } = value
+    const identifiers = omit(value, ['message'])
     const docId = hashObject(identifiers)
     try {
       const doc = await this.#dataType.getByDocId(docId)

src/utils.js

@@ -2,6 +2,7 @@ import sodium from 'sodium-universal'
 import { keyToPublicId } from '@mapeo/crypto'
 import { createHash } from 'node:crypto'
 import stableStringify from 'json-stable-stringify'
+import { omit } from './lib/omit.js'
 
 const PROJECT_INVITE_ID_SALT = Buffer.from('mapeo project invite id', 'ascii')
 
@@ -95,20 +96,16 @@ export function deNullify(obj) {
  * @returns {Omit<T, 'docId' | 'versionId' | 'originalVersionId' | 'links' | 'forks' | 'createdAt' | 'updatedAt' | 'deleted'>}
  */
 export function valueOf(doc) {
-  /* eslint-disable no-unused-vars */
-  const {
-    docId,
-    versionId,
-    originalVersionId,
-    links,
-    forks,
-    createdAt,
-    updatedAt,
-    deleted,
-    ...rest
-  } = doc
-  /* eslint-enable no-unused-vars */
-  return rest
+  return omit(doc, [
+    'docId',
+    'versionId',
+    'originalVersionId',
+    'links',
+    'forks',
+    'createdAt',
+    'updatedAt',
+    'deleted',
+  ])
 }
 
 /**

test/datastore.js

@@ -7,6 +7,7 @@ import { getVersionId } from '@comapeo/schema'
 import { once } from 'events'
 import RAM from 'random-access-memory'
 import { discoveryKey } from 'hypercore-crypto'
+import { omit } from '../src/lib/omit.js'
 
 /** @type {Omit<import('@comapeo/schema').Observation, 'versionId'>} */
 const obs = {
@@ -102,9 +103,7 @@ test('index events', async () => {
     storage: () => new RAM(),
   })
   dataStore.indexer.on('index-state', (state) => {
-    // eslint-disable-next-line no-unused-vars
-    const { entriesPerSecond, ...rest } = state
-    indexStates.push(rest)
+    indexStates.push(omit(state, ['entriesPerSecond']))
   })
   const idlePromise = once(dataStore.indexer, 'idle')
   await dataStore.write(obs)

test/lib/omit.js

@@ -0,0 +1,65 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { omit } from '../../src/lib/omit.js'
+
+test('an empty list of keys to omit', () => {
+  assert.deepEqual(omit({}, []), {})
+  assert.deepEqual(omit({ foo: 1 }, []), { foo: 1 })
+})
+
+test('omitting non-existent properties', () => {
+  assert.deepEqual(omit(record(), ['foo', 'bar']), {})
+  assert.deepEqual(omit(record({ foo: 1 }), ['bar', 'baz']), { foo: 1 })
+})
+
+test('omitting properties', () => {
+  const obj = { foo: 1, bar: 2, baz: 3 }
+  assert.deepEqual(omit(obj, ['baz']), { foo: 1, bar: 2 })
+  assert.deepEqual(omit(obj, ['bar', 'baz']), { foo: 1 })
+})
+
+test('only includes "own" properties in the result', () => {
+  class Klass {
+    foo = 1
+    bar = 2
+    baz() {
+      return 3
+    }
+  }
+
+  const omitted = omit(new Klass(), ['bar'])
+  assert.deepEqual(omitted, { foo: 1 }, 'plain object is returned')
+  assert(!(omitted instanceof Klass), 'inheritance is lost after omitting')
+  assert(!('baz' in omitted), 'inherited properties are lost after omitting')
+
+  const obj = new Klass()
+  obj.baz = () => 4
+  assert.equal(omit(obj, [])?.baz(), 4, 'own properties can be kept')
+  assert(!('baz' in omit(obj, ['baz'])), 'own properties can be removed')
+})
+
+test('only includes enumerable properties', () => {
+  const obj = { foo: 1 }
+  Object.defineProperty(obj, 'bar', { enumerable: true, value: 2 })
+  Object.defineProperty(obj, 'baz', { enumerable: false, value: 3 })
+
+  assert.deepEqual(omit(obj, ['foo']), { bar: 2 })
+})
+
+test("doesn't modify the input", () => {
+  const obj = { foo: 1, bar: 2, baz: 3 }
+  omit(obj, [])
+  omit(obj, ['foo', 'bar'])
+  assert.deepEqual(
+    obj,
+    { foo: 1, bar: 2, baz: 3 },
+    'input should not be modified'
+  )
+})
+
+/**
+ * Convenience helper to satisfy TypeScript.
+ * @param {Record<string, unknown>} [result]
+ * @returns {Record<string, unknown>}
+ */
+const record = (result = {}) => result

test/translation-api.js

@@ -13,6 +13,7 @@ import { createCoreManager } from './helpers/core-manager.js'
 import { IndexWriter } from '../src/index-writer/index.js'
 import RAM from 'random-access-memory'
 import { hashObject } from '../src/utils.js'
+import { omit } from '../src/lib/omit.js'
 import { randomBytes } from 'node:crypto'
 
 test('translation api - put() and get()', async () => {
@@ -43,8 +44,7 @@ test('translation api - put() and get()', async () => {
     'the map we use to caching translations is empty before calling put'
   )
 
-  /* eslint-disable no-unused-vars */
-  const { message, ...identifiers } = doc
+  const identifiers = omit(doc, ['message'])
   const expectedDocId = hashObject(identifiers)
   const { docId } = await api.put(doc)
   api.index(doc)
@@ -69,11 +69,8 @@ test('translation api - put() and get()', async () => {
     `we've effectively have fields in spanish`
   )
 
-  /* eslint-disable no-unused-vars */
-  const { schemaName, message: msg, ...docToGet } = doc
-
   assert.equal(
-    (await api.get(docToGet)).length,
+    (await api.get(doc)).length,
     1,
     `using the doc without schema name to get the translation works`
   )