Cleanup command line setting errors (elastic#124963)

This commit improves the error cases when command line settings are
found that are duplicates or conflict with special system properties.

Author: rjernst

distribution/tools/server-cli/src/test/java/org/elasticsearch/server/cli/ServerCliTests.java

@@ -185,7 +185,7 @@ public void testElasticsearchSettingCanNotBeEmpty() throws Exception {
     }
 
     public void testElasticsearchSettingCanNotBeDuplicated() throws Exception {
-        assertUsage(containsString("setting [foo] already set, saw [bar] and [baz]"), "-E", "foo=bar", "-E", "foo=baz");
+        assertUsage(containsString("setting [foo] set twice via command line -E"), "-E", "foo=bar", "-E", "foo=baz");
     }
 
     public void testUnknownOption() throws Exception {

server/src/main/java/org/elasticsearch/common/cli/EnvironmentAwareCommand.java

@@ -84,13 +84,7 @@ protected Environment createEnv(OptionSet options, ProcessInfo processInfo) thro
                 throw new UserException(ExitCodes.USAGE, "setting [" + kvp.key + "] must not be empty");
             }
             if (settings.containsKey(kvp.key)) {
-                final String message = String.format(
-                    Locale.ROOT,
-                    "setting [%s] already set, saw [%s] and [%s]",
-                    kvp.key,
-                    settings.get(kvp.key),
-                    kvp.value
-                );
+                final String message = String.format(Locale.ROOT, "setting [%s] set twice via command line -E", kvp.key);
                 throw new UserException(ExitCodes.USAGE, message);
             }
             settings.put(kvp.key, kvp.value);
@@ -133,18 +127,17 @@ private static void putSystemPropertyIfSettingIsMissing(
         final Map<String, String> settings,
         final String setting,
         final String key
-    ) {
+    ) throws UserException {
         final String value = sysprops.get(key);
         if (value != null) {
             if (settings.containsKey(setting)) {
                 final String message = String.format(
                     Locale.ROOT,
-                    "duplicate setting [%s] found via command-line [%s] and system property [%s]",
+                    "setting [%s] found via command-line -E and system property [%s]",
                     setting,
-                    settings.get(setting),
-                    value
+                    key
                 );
-                throw new IllegalArgumentException(message);
+                throw new UserException(ExitCodes.USAGE, message);
             } else {
                 settings.put(setting, value);
             }

server/src/test/java/org/elasticsearch/common/cli/EnvironmentAwareCommandTests.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.cli.CommandTestCase;
 import org.elasticsearch.cli.ProcessInfo;
 import org.elasticsearch.cli.Terminal;
+import org.elasticsearch.cli.UserException;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.env.Environment;
 import org.junit.Before;
@@ -127,4 +128,15 @@ public void testDockerEnvVarSettingsOverrideCommandLine() throws Exception {
         };
         execute("-Esimple.setting=original");
     }
+
+    public void testDuplicateCommandLineSetting() {
+        var e = expectThrows(UserException.class, () -> execute("-E", "my.setting=foo", "-E", "my.setting=bar"));
+        assertThat(e.getMessage(), equalTo("setting [my.setting] set twice via command line -E"));
+    }
+
+    public void testConflictingPathCommandLineSettingWithSysprop() {
+        sysprops.put("es.path.data", "foo");
+        var e = expectThrows(UserException.class, () -> execute("-E", "path.data=bar"));
+        assertThat(e.getMessage(), equalTo("setting [path.data] found via command-line -E and system property [es.path.data]"));
+    }
 }