From 464c15e52c82da5f1c86a088894e203439f1e65e Mon Sep 17 00:00:00 2001
From: Phillip Webb <pwebb@pivotal.io>
Date: Mon, 6 Apr 2020 17:29:59 -0700
Subject: [PATCH] Ensure empty layers are written to the index file

Update the `LayersIndex` class to ensure that layers that do not contain
content are still written.

Closes gh-20858
---
 .../org/springframework/boot/loader/tools/LayersIndex.java    | 4 ++--
 .../springframework/boot/loader/tools/LayersIndexTests.java   | 2 +-
 ...ts-writeToWhenAllFilesInFolderAreInSameLayerUsesFolder.txt | 1 +
 ...ersIndexTests-writeToWhenLayerNotUsedDoesNotSkipLayer.txt} | 1 +
 4 files changed, 5 insertions(+), 3 deletions(-)
 rename spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/{LayersIndexTests-writeToWhenLayerNotUsedSkipsLayer.txt => LayersIndexTests-writeToWhenLayerNotUsedDoesNotSkipLayer.txt} (87%)

diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayersIndex.java b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayersIndex.java
index fc770770c82..ab750ed568a 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayersIndex.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/LayersIndex.java
@@ -96,8 +96,8 @@ public class LayersIndex {
 		BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, StandardCharsets.UTF_8));
 		for (Layer layer : this.layers) {
 			List<String> names = index.get(layer);
-			if (names != null && !names.isEmpty()) {
-				writer.write("- \"" + layer + "\":\n");
+			writer.write("- \"" + layer + "\":\n");
+			if (names != null) {
 				for (String name : names) {
 					writer.write("  - \"" + name + "\"\n");
 				}
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/LayersIndexTests.java b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/LayersIndexTests.java
index 27ff4bf86aa..c162cf4ae0f 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/LayersIndexTests.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/LayersIndexTests.java
@@ -75,7 +75,7 @@ class LayersIndexTests {
 	}
 
 	@Test
-	void writeToWhenLayerNotUsedSkipsLayer() {
+	void writeToWhenLayerNotUsedDoesNotSkipLayer() {
 		LayersIndex index = new LayersIndex(LAYER_A, LAYER_B, LAYER_C);
 		index.add(LAYER_A, "a1");
 		index.add(LAYER_A, "a2");
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenAllFilesInFolderAreInSameLayerUsesFolder.txt b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenAllFilesInFolderAreInSameLayerUsesFolder.txt
index f18bd426563..c463bda16b5 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenAllFilesInFolderAreInSameLayerUsesFolder.txt
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenAllFilesInFolderAreInSameLayerUsesFolder.txt
@@ -2,3 +2,4 @@
   - "a1/"
 - "b":
   - "a2/"
+- "c":
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenLayerNotUsedSkipsLayer.txt b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenLayerNotUsedDoesNotSkipLayer.txt
similarity index 87%
rename from spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenLayerNotUsedSkipsLayer.txt
rename to spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenLayerNotUsedDoesNotSkipLayer.txt
index 4618afa671a..c895ed2aade 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenLayerNotUsedSkipsLayer.txt
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/resources/org/springframework/boot/loader/tools/LayersIndexTests-writeToWhenLayerNotUsedDoesNotSkipLayer.txt
@@ -1,6 +1,7 @@
 - "a":
   - "a1"
   - "a2"
+- "b":
 - "c":
   - "c1"
   - "c2"