From bae66feee45cb59241facc978c8fdd2bb4d4c751 Mon Sep 17 00:00:00 2001
From: Peter Hedenskog <phedenskog@wikimedia.org>
Date: Fri, 13 Sep 2019 01:55:54 +0200
Subject: [PATCH] fix: support merging deeply nested configuration (#1423)

---
 lib/apply-extends.js                     |  2 +-
 test/fixtures/extends/config_deep_2.json |  7 +++++++
 test/yargs.js                            | 17 +++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 test/fixtures/extends/config_deep_2.json

diff --git a/lib/apply-extends.js b/lib/apply-extends.js
index 20ded5e07..643c91335 100644
--- a/lib/apply-extends.js
+++ b/lib/apply-extends.js
@@ -56,7 +56,7 @@ function applyExtends (config, cwd, mergeExtends) {
 
     defaultConfig = isPath ? JSON.parse(fs.readFileSync(pathToDefault, 'utf8')) : require(config.extends)
     delete config.extends
-    defaultConfig = applyExtends(defaultConfig, path.dirname(pathToDefault))
+    defaultConfig = applyExtends(defaultConfig, path.dirname(pathToDefault), mergeExtends)
   }
 
   previouslyVisitedConfigs = []
diff --git a/test/fixtures/extends/config_deep_2.json b/test/fixtures/extends/config_deep_2.json
new file mode 100644
index 000000000..88c98258b
--- /dev/null
+++ b/test/fixtures/extends/config_deep_2.json
@@ -0,0 +1,7 @@
+{
+ "extends": "./config_deep.json",
+  "a": {
+    "b": 12,
+    "g": 1
+  }
+}
diff --git a/test/yargs.js b/test/yargs.js
index fcdd66941..795f1dcae 100644
--- a/test/yargs.js
+++ b/test/yargs.js
@@ -1402,6 +1402,23 @@ describe('yargs dsl tests', () => {
         argv.test.yes.should.equal(1)
       })
 
+      it('deep merges multiple configs when extending when deep-merge-config=true', () => {
+        const argv = yargs()
+          .parserConfiguration({ 'deep-merge-config': true })
+          .config({
+            extends: './test/fixtures/extends/config_deep_2.json',
+            a: {
+              g: 3
+            }
+          })
+          .parse()
+
+        argv.test.yes.should.equal(1)
+        argv.a.b.should.equal(12)
+        argv.a.c.should.equal(12)
+        argv.a.g.should.equal(3)
+      })
+
       it('does not deep merge objects by default', () => {
         const argv = yargs()
           .config({