Improve undefined values

src/config/normalize/lib/star_dot_path/entries.js

@@ -3,14 +3,6 @@ import { getObjectTokenType } from './tokens/main.js'
 
 // List all values (and their associated path) matching a specific query for
 // on specific target value.
-export const listExistingEntries = function (target, path) {
-  return listEntries(target, path).filter(isDefined)
-}
-
-const isDefined = function ({ defined }) {
-  return defined
-}
-
 export const listEntries = function (target, path) {
   return path.reduce(listTokenEntries, [
     { value: target, path: [], defined: true },

src/config/normalize/lib/star_dot_path/get.js

@@ -1,17 +1,30 @@
-import { listExistingEntries, normalizeEntry } from './entries.js'
+import { listEntries, normalizeEntry } from './entries.js'
 import { parse } from './parsing/parse.js'
 
 // Retrieve all properties in `target` matching a query string.
 export const list = function (target, queryOrPath) {
-  const path = parse(queryOrPath)
-  const entries = listExistingEntries(target, path)
+  const entries = listExistingEntries(target, queryOrPath)
   return entries.map(normalizeEntry)
 }
 
 // Retrieve a single property's value in `target` matching a query string.
 // Wildcards can be used, but only the first value is returned.
 export const get = function (target, queryOrPath) {
+  const entries = listExistingEntries(target, queryOrPath)
+  return entries.length === 0 ? undefined : entries[0].value
+}
+
+// Check if a property is defined according to a query
+export const has = function (target, queryOrPath) {
+  const entries = listExistingEntries(target, queryOrPath)
+  return entries.length !== 0
+}
+
+const listExistingEntries = function (target, queryOrPath) {
   const path = parse(queryOrPath)
-  const [entry] = listExistingEntries(target, path)
-  return entry === undefined ? undefined : entry.value
+  return listEntries(target, path).filter(isDefined)
+}
+
+const isDefined = function ({ defined }) {
+  return defined
 }

src/config/normalize/lib/star_dot_path/main.js

@@ -1,5 +1,4 @@
-export { list, get } from './get.js'
-export { has } from './has.js'
+export { list, get, has } from './get.js'
 export { equals, parent } from './parsing/compare.js'
 export { serialize } from './parsing/serialize.js'
 export { parse } from './parsing/parse.js'

src/config/normalize/lib/star_dot_path/tokens/array.js

@@ -40,11 +40,14 @@ const getEntries = function (value, path, token) {
 }
 
 // Retrieve an array using a positive or negative index.
-// Indices that are out-of-bound return no entries but do not error.
-const getArrayIndex = function (array, token) {
+// Indices that are out-of-bound:
+//  - Do not error
+//  - Return an entry with an `undefined` value
+//     - This allows appending to arrays, e.g. with -0
+const getArrayIndex = function (value, token) {
   return token > 0 || Object.is(token, +0)
     ? token
-    : Math.max(array.length + token, 0)
+    : Math.max(value.length + token, 0)
 }
 
 // Check if two tokens are the same

src/config/normalize/lib/star_dot_path/tokens/prop.js

@@ -31,8 +31,11 @@ const isDefined = function (value) {
 const defaultValue = {}
 
 // Use the token to list entries against a target value.
+// We distinguish between:
+//  - Missing property name: return no entries
+//  - Property exists but has `undefined` value: return an entry
 const getEntries = function (value, path, token) {
-  return [{ value: value[token], path: [...path, token] }]
+  return token in value ? [{ value: value[token], path: [...path, token] }] : []
 }
 
 // Check if two tokens are the same