Installation on a non-composer-installed Drupal8?

Hello!
Thank you for interesting in to my module. Sorry for long term of reply. I've installed all dependencies with Composer and didn't try to use it without Composer.

Is it possible that with your composer installation that you can locate the library files from your site's root directory? I think the path from the root directory to the library file name is most of what I actually need. If I need more than that I will figure out what that is after getting the library into the correct location within the site. Thanks for this module.

Hello!
When you will install this module with composer - League libraries will be installed automatically to
vendor/league/oauth2-client and
vendor/league/oauth2-linkedin.
My understanding is - you need to download and place these libraries to vendor/league folder.
You can find these libraries here http://oauth2-client.thephpleague.com/providers/league/
or on github https://github.com/thephpleague/oauth2-client
https://github.com/thephpleague/oauth2-linkedin

If you have any questions - please ask me. I will try to answer as soon as possible.

I am using a non-composer drupal 8 instance. I have downloaded the oauth2-client and oauth2-linkedin libraries from the links mentioned in #4 and pasted them in the path "/vendor/league". In the Get Linkedin Posts settings, I have given company ID, client id and client secret. But when I tried to click on the button "Get new linkedin access token", I got an error "The website encountered an unexpected error. Please try again later.". In the recent log messages, I have found the following error :

Error: Class 'League\OAuth2\Client\Provider\LinkedIn' not found in Drupal\get_linkedin_posts\Form\GetLinkedinPostsSettings->getNewLinkedinToken() (line 174 of /opt/web/modules/contrib/get_linkedin_posts/src/Form/GetLinkedinPostsSettings.php) #0 [internal function]: Drupal\get_linkedin_posts\Form\GetLinkedinPostsSettings->getNewLinkedinToken(Array, Object(Drupal\Core\Form\FormState)) #1 /opt/web/core/lib/Drupal/Core/Form/FormSubmitter.php(111): call_user_func_array(Array, Array) #2 /opt/web/core/lib/Drupal/Core/Form/FormSubmitter.php(51): Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object(Drupal\Core\Form\FormState)) #3 /opt/web/core/lib/Drupal/Core/Form/FormBuilder.php(590): Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object(Drupal\Core\Form\FormState)) #4 /opt/web/core/lib/Drupal/Core/Form/FormBuilder.php(319): Drupal\Core\Form\FormBuilder->processForm('get_linkedin_po...', Array, Object(Drupal\Core\Form\FormState)) #5 /opt/web/core/lib/Drupal/Core/Controller/FormController.php(93): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\get_linkedin_posts\Form\GetLinkedinPostsSettings), Object(Drupal\Core\Form\FormState)) #6 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch)) #7 /opt/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array) #8 /opt/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #9 /opt/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #10 /opt/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) #11 /opt/web/vendor/symfony/http-kernel/HttpKernel.php(151): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #12 /opt/web/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) #13 /opt/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #14 /opt/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #15 /opt/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #16 /opt/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) #17 /opt/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #18 /opt/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #19 /opt/web/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #20 /opt/web/core/lib/Drupal/Core/DrupalKernel.php(693): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #21 /opt/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) #22 {main}.

Is there any solution to this?

Please refrain from hijacking old issues. Create your own issue for more assistance and relate to this one.

It is expected to use Composer to introduce this module to your code base. The Composer autoload feature will make sure classes are found.
To answer the question: There is Ludwig for introducing modules with dependencies without using Composer.

Obviously, these things can be solved manually. Expect that beyond the support provided for this module. Even when using the right API.
Definitely not a bug report !