Add quotes on composed flatten keys.

sources/yaml/src/main/java/io/smallrye/config/source/yaml/YamlConfigSource.java

@@ -98,6 +98,10 @@ private static Map<String, String> yamlInputToMap(final Map<String, Object> yaml
     @SuppressWarnings("unchecked")
     private static void flattenYaml(String path, Map<String, Object> source, Map<String, String> target) {
         source.forEach((key, value) -> {
+            if (key != null && key.indexOf('.') != -1) {
+                key = "\"" + key + "\"";
+            }
+
             if (key != null && !key.isEmpty() && path != null && !path.isEmpty()) {
                 key = path + "." + key;
             } else if (path != null && !path.isEmpty()) {
@@ -138,6 +142,17 @@ private static void flattenList(String key, List<Object> source, Map<String, Str
         }
     }
 
+    private static void escapeQuotes(StringBuilder b, String src) {
+        int cp;
+        for (int i = 0; i < src.length(); i += Character.charCount(cp)) {
+            cp = src.codePointAt(i);
+            if (cp == '\\' || cp == '"') {
+                b.append('\\');
+            }
+            b.appendCodePoint(cp);
+        }
+    }
+
     private static void escapeCommas(StringBuilder b, String src, int escapeLevel) {
         int cp;
         for (int i = 0; i < src.length(); i += Character.charCount(cp)) {

sources/yaml/src/test/java/io/smallrye/config/source/yaml/YamlConfigSourceTest.java

@@ -3,6 +3,7 @@
 import static java.util.stream.Collectors.toList;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.ArrayList;
@@ -96,6 +97,22 @@ void propertyNames() throws Exception {
         assertEquals("TLSv1.3", config.getRawValue("quarkus.http.ssl.protocols.[1]"));
     }
 
+    @Test
+    void quotedProperties() throws Exception {
+        SmallRyeConfig config = new SmallRyeConfigBuilder()
+                .withSources(
+                        new YamlConfigSource("yaml", YamlConfigSourceTest.class.getResourceAsStream("/example-quotes.yml")))
+                .withConverter(Users.class, 100, new UserConverter())
+                .build();
+
+        final List<String> propertyNames = StreamSupport.stream(config.getPropertyNames().spliterator(), false)
+                .collect(toList());
+
+        assertTrue(propertyNames.contains("quarkus.log.category.liquibase.level"));
+        assertTrue(propertyNames.contains("quarkus.log.category.\"liquibase.changelog.ChangeSet\".level"));
+        assertNotNull(config.getRawValue("quarkus.log.category.\"liquibase.changelog.ChangeSet\".level"));
+    }
+
     public static class Users {
         List<User> users;
 

sources/yaml/src/test/resources/example-quotes.yml

@@ -0,0 +1,7 @@
+quarkus:
+  log:
+    category:
+      "liquibase.changelog.ChangeSet":
+        level: INFO
+      "liquibase":
+        level: WARN