Split out a helper method for parsing only application overrides

config/src/main/java/com/typesafe/config/ConfigFactory.java

@@ -8,7 +8,7 @@
 
 import java.io.File;
 import java.io.Reader;
-import java.net.URL;
+import java.net.*;
 import java.util.Map;
 import java.util.Properties;
 import java.util.concurrent.Callable;
@@ -1090,6 +1090,63 @@ public static Config parseResourcesAnySyntax(String resourceBasename) {
         return parseResourcesAnySyntax(resourceBasename, ConfigParseOptions.defaults());
     }
 
+    /**
+     * Parse only any application overrides (those specified by config.{resource,file,url}), returning
+     * an empty Config if no overrides were set.
+     * @param parseOptions parse options
+     * @return the parsed configuration
+     */
+    public static Config parseApplicationOverride(ConfigParseOptions parseOptions) {
+        ClassLoader loader = parseOptions.getClassLoader();
+
+        if (loader == null)
+            throw new ConfigException.BugOrBroken(
+                "ClassLoader should have been set here; bug in ConfigFactory. "
+                    + "(You can probably work around this bug by passing in a class loader or calling currentThread().setContextClassLoader() though.)");
+
+        int specified = 0;
+
+        // override application.conf with config.file, config.resource,
+        // config.url if requested.
+        String resource = System.getProperty("config.resource");
+        if (resource != null)
+            specified += 1;
+        String file = System.getProperty("config.file");
+        if (file != null)
+            specified += 1;
+        String url = System.getProperty("config.url");
+        if (url != null)
+            specified += 1;
+
+        if (specified == 0) {
+            return ConfigImpl.emptyConfig("TODO: what to put here? Should something else be returned?");
+        } else if (specified > 1) {
+            throw new ConfigException.Generic("You set more than one of config.file='" + file
+                + "', config.url='" + url + "', config.resource='" + resource
+                + "'; don't know which one to use!");
+        } else {
+            // the override file/url/resource MUST be present or it's an error
+            ConfigParseOptions overrideOptions = parseOptions.setAllowMissing(false);
+            if (resource != null) {
+                if (resource.startsWith("/"))
+                    resource = resource.substring(1);
+                // this deliberately does not parseResourcesAnySyntax; if
+                // people want that they can use an include statement.
+                return ConfigFactory.parseResources(loader, resource, overrideOptions);
+            } else if (file != null) {
+                return ConfigFactory.parseFile(new File(file), overrideOptions);
+            } else {
+                try {
+                    return ConfigFactory.parseURL(new URL(url), overrideOptions);
+                } catch (MalformedURLException e) {
+                    throw new ConfigException.Generic("Bad URL in config.url system property: '"
+                        + url + "': " + e.getMessage(), e);
+                }
+            }
+        }
+
+    }
+
     /**
      * Parses a string (which should be valid HOCON or JSON by default, or
      * the syntax specified in the options otherwise).

config/src/main/java/com/typesafe/config/DefaultConfigLoadingStrategy.java

@@ -1,5 +1,7 @@
 package com.typesafe.config;
 
+import com.typesafe.config.impl.*;
+
 import java.io.File;
 import java.net.MalformedURLException;
 import java.net.URL;
@@ -12,51 +14,11 @@
 public class DefaultConfigLoadingStrategy implements ConfigLoadingStrategy {
     @Override
     public Config parseApplicationConfig(ConfigParseOptions parseOptions) {
-        ClassLoader loader = parseOptions.getClassLoader();
-        if (loader == null)
-            throw new ConfigException.BugOrBroken(
-                    "ClassLoader should have been set here; bug in ConfigFactory. "
-                            + "(You can probably work around this bug by passing in a class loader or calling currentThread().setContextClassLoader() though.)");
-
-        int specified = 0;
-
-        // override application.conf with config.file, config.resource,
-        // config.url if requested.
-        String resource = System.getProperty("config.resource");
-        if (resource != null)
-            specified += 1;
-        String file = System.getProperty("config.file");
-        if (file != null)
-            specified += 1;
-        String url = System.getProperty("config.url");
-        if (url != null)
-            specified += 1;
-
-        if (specified == 0) {
+        Config overrideConfig = ConfigFactory.parseApplicationOverride(parseOptions);
+        if (overrideConfig.isEmpty()) {
             return ConfigFactory.parseResourcesAnySyntax("application", parseOptions);
-        } else if (specified > 1) {
-            throw new ConfigException.Generic("You set more than one of config.file='" + file
-                                                      + "', config.url='" + url + "', config.resource='" + resource
-                                                      + "'; don't know which one to use!");
         } else {
-            // the override file/url/resource MUST be present or it's an error
-            ConfigParseOptions overrideOptions = parseOptions.setAllowMissing(false);
-            if (resource != null) {
-                if (resource.startsWith("/"))
-                    resource = resource.substring(1);
-                // this deliberately does not parseResourcesAnySyntax; if
-                // people want that they can use an include statement.
-                return ConfigFactory.parseResources(loader, resource, overrideOptions);
-            } else if (file != null) {
-                return ConfigFactory.parseFile(new File(file), overrideOptions);
-            } else {
-                try {
-                    return ConfigFactory.parseURL(new URL(url), overrideOptions);
-                } catch (MalformedURLException e) {
-                    throw new ConfigException.Generic("Bad URL in config.url system property: '"
-                                                              + url + "': " + e.getMessage(), e);
-                }
-            }
+            return overrideConfig;
         }
     }
 }

config/src/main/main.iml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/java" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

config/src/test/test.iml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/java" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/scala" isTestSource="true" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="module" module-name="main" />
+  </component>
+</module>