Pr/liven/fix placeholder subtitution

src/main/java/me/itzg/helpers/env/SimplePlaceholders.java

@@ -39,7 +39,11 @@ public String processPlaceholders(String value) {
             do {
                 final String type = Optional.ofNullable(m.group("type"))
                     .orElse("env");
-                final String replacement = buildPlaceholderReplacement(type, m.group("var"), m.group());
+                final String replacement = buildPlaceholderReplacement(type, m.group("var"));
+
+                if (replacement == null) {
+                    continue;
+                }
 
                 m.appendReplacement(sb, replacement);
             } while (m.find());
@@ -50,18 +54,15 @@ public String processPlaceholders(String value) {
         return value;
     }
 
-    private String buildPlaceholderReplacement(String type, String var, String fallback) {
+    private String buildPlaceholderReplacement(String type, String var) {
         log.debug("Building placeholder replacement from type={} with var='{}'", type, var);
         switch (type) {
             case "env":
                 final String result = environmentVariablesProvider.get(var);
-                if (result != null) {
-                    return result;
-                }
-                else {
+                if (result == null) {
                     log.warn("Unable to resolve environment variable {}", var);
-                    return fallback;
                 }
+                return result;
 
             case "date":
             case "time":
@@ -70,11 +71,11 @@ private String buildPlaceholderReplacement(String type, String var, String fallb
                     return ZonedDateTime.now(clock).format(f);
                 } catch (IllegalArgumentException e) {
                     log.error("Invalid date/time format in {}", var, e);
-                    return fallback;
+                    return null;
                 }
         }
 
-        return fallback;
+        return null;
     }
 
 }

src/test/java/me/itzg/helpers/properties/SetPropertiesCommandTest.java

@@ -289,6 +289,28 @@ void processesPlaceholders(String motd, String expected) {
 
     }
 
+    @Test
+    void complexSecretsProcessedCorrectly() throws Exception {
+        final String secret = ":xDmW!T5Y%Jjam;$L9adz-tf%4BuhN,z#64pGx+;3R6^W$#PgGv!Nm-*)A}3^*/js*&)#";
+
+        final int exitCode = new CommandLine(new SetPropertiesCommand()
+            .setEnvironmentVariablesProvider(MappedEnvVarProvider.of(
+                "RCON_PASSWORD", secret
+            ))
+        )
+            .execute(
+                "--definitions", definitionsFile.toString(),
+                propertiesFile.toString()
+            );
+
+        assertThat(exitCode).isEqualTo(ExitCode.OK);
+
+        final Properties properties = loadProperties();
+
+        assertThat(properties).containsEntry("rcon.password", secret);
+        assertPropertiesEqualExcept(properties, "rcon.password");
+    }
+
     private void assertPropertiesEqualExcept(Properties properties, String... propertiesToIgnore) {
         final HashSet<Object> actualKeys = new HashSet<>(properties.keySet());
         Arrays.asList(propertiesToIgnore).forEach(actualKeys::remove);

src/test/resources/properties/property-definitions.json

@@ -72,6 +72,9 @@
   "compression-threshold": {
     "env": "COMPRESSION_THRESHOLD"
   },
+  "rcon.password": {
+    "env": "RCON_PASSWORD"
+  },
   "level-name": {
     "env": "LEVEL_NAME"
   },