Adding config-help command

Author: hrachya

modules/swagger-codegen-cli/src/main/java/com/wordnik/swagger/codegen/SwaggerCodegen.java

@@ -1,5 +1,6 @@
 package com.wordnik.swagger.codegen;
 
+import com.wordnik.swagger.codegen.cmd.ConfigHelp;
 import com.wordnik.swagger.codegen.cmd.Generate;
 import com.wordnik.swagger.codegen.cmd.Langs;
 import com.wordnik.swagger.codegen.cmd.Meta;
@@ -27,7 +28,8 @@ public static void main(String[] args) {
                         Generate.class,
                         Meta.class,
                         Langs.class,
-                        Help.class
+                        Help.class,
+                        ConfigHelp.class
                 );
 
         builder.build().parse(args).run();

modules/swagger-codegen-cli/src/main/java/com/wordnik/swagger/codegen/cmd/ConfigHelp.java

@@ -0,0 +1,54 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package com.wordnik.swagger.codegen.cmd;
+
+import com.wordnik.swagger.codegen.CliOption;
+import com.wordnik.swagger.codegen.CodegenConfig;
+import io.airlift.airline.Command;
+import io.airlift.airline.Option;
+import java.util.ServiceLoader;
+import static java.util.ServiceLoader.load;
+
+@Command(name = "config-help", description = "Config help for chosen lang")
+public class ConfigHelp implements Runnable {
+    
+    @Option(name = {"-l", "--lang"}, title = "language", required = true,
+            description = "language to get config help for")
+    private String lang;
+
+    @Override
+    public void run() {
+        System.out.println();
+        CodegenConfig config = forName(lang);
+        System.out.println("CONFIG OPTIONS");
+        for (CliOption langCliOption : config.cliOptions()) {
+            System.out.println("\t" + langCliOption.getOpt());
+            System.out.println("\t    " + langCliOption.getDescription());
+            System.out.println();
+        }
+    }
+    
+    /**
+     * Tries to load config class with SPI first, then with class name directly from classpath
+     * @param name name of config, or full qualified class name in classpath
+     * @return config class
+     */
+    private static CodegenConfig forName(String name) {
+        ServiceLoader<CodegenConfig> loader = load(CodegenConfig.class);
+        for (CodegenConfig config : loader) {
+            if (config.getName().equals(name)) {
+                return config;
+            }
+        }
+
+        // else try to load directly
+        try {
+            return (CodegenConfig) Class.forName(name).newInstance();
+        } catch (Exception e) {
+            throw new RuntimeException("Can't load config class with name ".concat(name), e);
+        }
+    }
+}

modules/swagger-codegen-cli/src/main/java/com/wordnik/swagger/codegen/cmd/Generate.java

@@ -61,7 +61,9 @@ public class Generate implements Runnable {
             "the format of name=value,name=value")
     private String systemProperties;
 
-    @Option( name= {"-c", "--config"}, title = "configuration file", description = "path to json configuration file")
+    @Option( name= {"-c", "--config"}, title = "configuration file", description = "Path to json configuration file. " +
+            "File content should be in a json format {\"optionKey\":\"optionValue\", \"optionKey1\":\"optionValue1\"...} " +
+            "Supported options can be different for each language. Run config-help -l {lang} command for language specific config options.")
     private String configFile;
 
     @Override