Update docs and add more helpful output to validate command, refs #9782

doc/04-schema.md

@@ -94,7 +94,9 @@ Out of the box, Composer supports four types:
   CMSs like the [SilverStripe installer](https://github.com/silverstripe/silverstripe-installer)
   or full fledged applications distributed as packages. This can for example
   be used by IDEs to provide listings of projects to initialize when creating
-  a new workspace.
+  a new workspace.  Setting the type to `project` also makes the `name` and
+  `description` fields optional, making it a good choice for closed source
+  projects wishing to use `composer validate`.
 - **metapackage:** An empty package that contains requirements and will trigger
   their installation, but contains no files and will not write anything to the
   filesystem. As such, it does not require a dist or source key to be

src/Composer/Util/ConfigValidator.php

@@ -63,6 +63,16 @@ class ConfigValidator
             $json->validateSchema();
         } catch (JsonValidationException $e) {
             foreach ($e->getErrors() as $message) {
+                if ($message === 'type : The property type is required') {
+                    $message .= ' (see https://getcomposer.org/doc/04-schema.md#type)';
+                }
+                if ($message === 'name : The property name is required') {
+                    $message .= ' (or set "type" to "project" to remove this requirement)';
+                }
+                if ($message === 'description : The property description is required') {
+                    $message .= ' (or set "type" to "project" to remove this requirement)';
+                }
+
                 if ($laxValid) {
                     $publishErrors[] = $message;
                 } else {