Allow using square brackets in map keys

implementation/src/main/java/io/smallrye/config/ConfigMappingProvider.java

@@ -657,17 +657,19 @@ public void accept(final ConfigMappingContext context, final NameIterator ni) {
         }
 
         private String mapKey(final NameIterator ni) {
-            NameIterator mapPath = new NameIterator(normalizeIfIndexed(this.mapPath));
-            NameIterator mapKey = new NameIterator(normalizeIfIndexed(ni.getName()));
-            while (mapPath.hasNext() && mapKey.hasNext()) {
-                if (mapPath.getNextSegment().equals(mapKey.getNextSegment()) || mapPath.getNextSegment().equals("*")) {
+            NameIterator mapPath = new NameIterator(this.mapPath);
+            NameIterator mapPathKey = new NameIterator(anyIfIndexed(ni.getName()));
+            NameIterator mapRealKey = new NameIterator(ni.getName());
+            while (mapPath.hasNext() && mapPathKey.hasNext()) {
+                if (mapPath.getNextSegment().equals(mapPathKey.getNextSegment()) || mapPath.getNextSegment().equals("*")) {
                     mapPath.next();
-                    mapKey.next();
+                    mapPathKey.next();
+                    mapRealKey.next();
                 } else {
                     break;
                 }
             }
-            return mapKey.hasNext() ? mapKey.getNextSegment() : ni.getPreviousSegment();
+            return mapRealKey.hasNext() ? mapRealKey.getNextSegment() : ni.getPreviousSegment();
         }
     }
 
@@ -859,6 +861,25 @@ private static String normalizeIfIndexed(final String propertyName) {
         return propertyName;
     }
 
+    private static String anyIfIndexed(final String propertyName) {
+        StringBuilder builder = new StringBuilder();
+
+        int pos = 0;
+        for (int i = 0; i < propertyName.length(); i++) {
+            if (propertyName.charAt(i) == '[') {
+                builder.append(propertyName, pos, i + 1);
+                pos = i;
+            } else if (propertyName.charAt(i) == ']') {
+                builder.append("*");
+                builder.append(propertyName, i, i + 1);
+                pos = i + 1;
+            }
+        }
+        builder.append(propertyName, pos, propertyName.length());
+
+        return builder.toString();
+    }
+
     private static boolean validateUnknown(final boolean validateUnknown, final SmallRyeConfig config) {
         return config.getOptionalValue(SMALLRYE_CONFIG_MAPPING_VALIDATE_UNKNOWN, Boolean.class)
                 .orElse(validateUnknown);

implementation/src/main/java/io/smallrye/config/KeyMap.java

@@ -136,7 +136,7 @@ private KeyMap<V> findOrDefault(final String seg) {
         KeyMap<V> next = getOrDefault(seg, any);
         if (seg.endsWith("]")) {
             int begin = seg.lastIndexOf('[');
-            if (begin != -1) {
+            if (begin != -1 && isValidIndex(seg, begin)) {
                 next = getOrDefault(seg.substring(0, begin), any);
                 if (next != null) {
                     next = next.find("[");
@@ -152,6 +152,19 @@ private KeyMap<V> findOrDefault(final String seg) {
         return next;
     }
 
+    private boolean isValidIndex(final String seg, final int begin) {
+        try {
+            String index = seg.substring(begin + 1, seg.length() - 1);
+            if (index.equals("*")) {
+                return true;
+            }
+            Integer.parseInt(index);
+            return true;
+        } catch (NumberFormatException e) {
+            return false;
+        }
+    }
+
     public KeyMap<V> findOrAdd(final String path) {
         return findOrAdd(new NameIterator(path));
     }

implementation/src/test/java/io/smallrye/config/ConfigMappingCollectionsTest.java

@@ -499,4 +499,24 @@ void mappingCollectionsMap() {
         assertTrue(mapping.present().isPresent());
         assertEquals("localhost", mapping.present().get().get(0).get("localhost"));
     }
+
+    public interface MapKeyWithIndexedSyntax {
+        Map<String, String> map();
+    }
+
+    @Test
+    void mapKeyWithIndexedSyntax() {
+        SmallRyeConfig config = new SmallRyeConfigBuilder()
+                .withMapping(MapKeyWithIndexedSyntax.class)
+                .withSources(config("map.key", "value"))
+                .withSources(config("map.key[x]", "value"))
+                .withSources(config("map.key[0-9]", "value"))
+                .build();
+
+        MapKeyWithIndexedSyntax mapping = config.getConfigMapping(MapKeyWithIndexedSyntax.class);
+
+        assertEquals("value", mapping.map().get("key"));
+        assertEquals("value", mapping.map().get("key[x]"));
+        assertEquals("value", mapping.map().get("key[0-9]"));
+    }
 }