fix(yaml): add conflict handling

libraries/yaml/source/extensions/$import.js

@@ -1,9 +1,16 @@
 'use strict'
 
 const { resolve, dirname } = require('node:path')
-const { traverse, merge } = require('@toa.io/generic')
+const { traverse, add } = require('@toa.io/generic')
 const { file } = require('@toa.io/filesystem')
 
+/** @type {toa.yaml.extension} */
+const $import = (object, path, yaml) => {
+  return traverse(object, (node) => {
+    if ('$import' in node) extend(node, path, yaml)
+  })
+}
+
 /**
  * @param {{$import: string}} node
  * @param {string} [path]
@@ -17,14 +24,7 @@ function extend (node, path, yaml) {
 
   delete node.$import
 
-  return objects.reduce((node, object) => merge(node, object), node)
-}
-
-/** @type {toa.yaml.extension} */
-const $import = (object, path, yaml) => {
-  return traverse(object, (node) => {
-    if ('$import' in node) extend(node, path, yaml)
-  })
+  return objects.reduce((node, object) => add(node, object), node)
 }
 
 module.exports = $import

libraries/yaml/test/examples/imports/conflicts/a.yaml

@@ -0,0 +1,4 @@
+$import: ./b.yaml
+foo: 1
+obj:
+  bar: 1

libraries/yaml/test/examples/imports/conflicts/b.yaml

@@ -0,0 +1,5 @@
+foo: 2
+baz: 2
+obj:
+  bar: 2
+  baz: 2

libraries/yaml/test/import.test.js

@@ -3,43 +3,51 @@
 const { resolve } = require('node:path')
 const { load } = require('../source')
 
-describe('basic', () => {
-  it('should import files', async () => {
-    const path = resolve(__dirname, './examples/imports/basic/c.yaml')
-    const object = await load(path)
+it('should import files', async () => {
+  const path = resolve(__dirname, './examples/imports/basic/c.yaml')
+  const object = await load(path)
 
-    expect(object).toStrictEqual({
+  expect(object).toStrictEqual({
+    foo: {
+      bar: 1,
+      baz: 2
+    },
+    qux: 'hello'
+  })
+})
+
+it('should import recursively', async () => {
+  const path = resolve(__dirname, './examples/imports/nested/c.yaml')
+  const object = await load(path)
+
+  expect(object).toStrictEqual({
+    result: {
       foo: {
         bar: 1,
         baz: 2
       },
       qux: 'hello'
-    })
+    }
   })
 })
 
-describe('nested', () => {
-  it('should import files', async () => {
-    const path = resolve(__dirname, './examples/imports/nested/c.yaml')
-    const object = await load(path)
-
-    expect(object).toStrictEqual({
-      result: {
-        foo: {
-          bar: 1,
-          baz: 2
-        },
-        qux: 'hello'
-      }
-    })
+it('should not overwrite existing values', async () => {
+  const path = resolve(__dirname, './examples/imports/conflicts/a.yaml')
+  const object = await load(path)
+
+  expect(object).toStrictEqual({
+    foo: 1,
+    baz: 2,
+    obj: {
+      bar: 1,
+      baz: 2
+    }
   })
 })
 
-describe('multidoc', () => {
-  it('should import files', async () => {
-    const path = resolve(__dirname, './examples/imports/multidoc/a.yaml')
-    const object = await load.all(path)
+it('should import within multidoc files', async () => {
+  const path = resolve(__dirname, './examples/imports/multidoc/a.yaml')
+  const object = await load.all(path)
 
-    expect(object).toStrictEqual([{ foo: { bar: 1 } }, { qux: 'hello' }])
-  })
+  expect(object).toStrictEqual([{ foo: { bar: 1 } }, { qux: 'hello' }])
 })