Fix: Update types to support union-type arguments (Fixes#10)

This commit updates the signature of the `PluginError` constructor to
loosen the constraints on the parameters in order to support union types
while keeping inference on custom properties.
This is a semver minor update (fix).
This allows for example to use the pattern below:
```
function createPluginError(error: Error | string) {
return new PluginError("test", error);
}
```
(The tests were updated with more complex cases)
See the discussions in #10 and #11 for details.
- Closes#10
- Closes#11
/cc @gucong3000

Author: demurgos

index.d.ts

@@ -1,29 +1,29 @@
 declarenamespacePluginError{
-exportinterfaceConstructor{
+interfaceConstructor{
 /**
- * @param options Options with plugin name and message
+ * @param plugin Plugin name
+ * @param error Base error
+ * @param options Error options
  */
-new(options: Options&{plugin: string,message: string}): PluginError;
+new<EextendsError>(plugin: string,error: E,options?: Options): PluginError<E>;
 
 /**
  * @param plugin Plugin name
- * @parammessage Error message
+ * @paramerror Base error or error message
  * @param options Error options
  */
-new(plugin: string,message: string,options?: Options): PluginError;
+new<EextendsError=Error>(plugin: string,error: E|string,options: Options): PluginError<E|{[KinkeyofE]: undefined}>;
 
 /**
  * @param plugin Plugin name
- * @param error Base error
- * @param options Error options
+ * @param error Base error, error message, or options with message
  */
-new<EextendsError>(plugin: string,error: E,options?: Options): PluginError<E>;
+new<EextendsError=Error>(plugin: string,error: E|string|(Options&{message: string})): PluginError<E|{[KinkeyofE]: undefined}>;
 
 /**
- * @param plugin Plugin name
- * @param options Options with message
+ * @param options Options with plugin name and message
  */
-new(plugin: string,options: Options&{message: string}): PluginError;
+new(options: Options&{plugin: string,message: string}): PluginError;
 }
 
 interfaceOptions{
@@ -71,11 +71,12 @@ declare namespace PluginError {
 stack?: string;
 }
 
-
 /**
- * The `Base` interface defines the properties available on all the the instances of `PluginError`.
+ * The `SimplePluginError` interface defines the properties available on all the the instances of `PluginError`.
+ *
+ * @internal
  */
-exportinterfaceBaseextendsError{
+interfaceSimplePluginErrorextendsError{
 /**
  * Plugin name
  */
@@ -106,7 +107,7 @@ declare namespace PluginError {
 /**
  * Abstraction for error handling for Vinyl plugins
  */
-typePluginError<T={}>=PluginError.Base&T;
+typePluginError<T={}>=PluginError.SimplePluginError&T;
 
 declareconstPluginError: PluginError.Constructor;
 

test/types/test.ts

@@ -26,7 +26,8 @@ import PluginError = require("plugin-error");
 
 {
 constexistingError=newError("OMG");
-consterr=newPluginError("test",existingError,{showStack: true});
+constoptions: PluginError.Options={showStack: true};
+consterr=newPluginError("test",existingError,options);
 }
 }
 
@@ -51,3 +52,87 @@ import PluginError = require("plugin-error");
 }
 }
 
+{
+// Union types
+constPLUGIN_NAME: string="test";
+
+interfaceFooErrorextendsError{
+foo: number;
+}
+
+constERROR: Error=newError("something broke");
+constFOO_ERROR: FooError=Object.assign(newError("something broke"),{foo: 1});
+constMESSAGE: string="something broke";
+constOPTIONS: {message: string}={message: "something broke"};
+
+{
+functioncreateError(error: Error|string){
+returnnewPluginError(PLUGIN_NAME,error);
+}
+constpluginError1=createError(ERROR);
+constpluginError2=createError(FOO_ERROR);
+constpluginError3=createError(MESSAGE);
+// The following code should cause a compilation error:
+// const foo: any = pluginError2.foo;
+}
+
+{
+// Make sure that custom properties are preserved
+functioncreateError(error: FooError){
+returnnewPluginError(PLUGIN_NAME,error);
+}
+constpluginError=createError(FOO_ERROR);
+constfoo: number=pluginError.foo;
+}
+
+{
+// Just check that there's no issue when building it with a string
+functioncreateError(error: string){
+returnnewPluginError(PLUGIN_NAME,error);
+}
+constpluginError=createError(MESSAGE);
+// The following code should cause a compilation error:
+// const foo: any = pluginError.foo;
+}
+
+{
+// Check that custom properties are preserved but marked as potentially missing
+// The `foo` property must be of type `number | undefined` because it's existence depends
+// on the way `createError` is called.
+functioncreateError(error: FooError|string){
+returnnewPluginError(PLUGIN_NAME,error);
+}
+
+constpluginError1=createError(FOO_ERROR);
+constfoo1: number|undefined=pluginError1.foo;
+// The following code should cause a compilation error:
+// const foo2: number = pluginError1.foo;
+
+constpluginError2=createError(MESSAGE);
+constfoo3: number|undefined=pluginError2.foo;
+// The following code should cause a compilation error:
+// const foo4: number = pluginError2.foo;
+}
+
+{
+// Check support for unions with option object
+functioncreateError(error: FooError|string|(PluginError.Options&{message: string})){
+returnnewPluginError(PLUGIN_NAME,error);
+}
+
+constpluginError1=createError(FOO_ERROR);
+constfoo1: number|undefined=pluginError1.foo;
+// The following code should cause a compilation error:
+// const foo2: number = pluginError1.foo;
+
+constpluginError2=createError(MESSAGE);
+constfoo3: number|undefined=pluginError2.foo;
+// The following code should cause a compilation error:
+// const foo4: number = pluginError2.foo;
+
+constpluginError3=createError(OPTIONS);
+constfoo5: number|undefined=pluginError3.foo;
+// The following code should cause a compilation error:
+// const foo6: number = pluginError3.foo;
+}
+}