tl;dr
In Chrome DevTools in the Elements tab or in Firefox in the Inspector tab you can right click on an element and choose Break on to debug changes related to this element.
DOM Breakpoints can be quite useful to quickly find the JavaScript that is responsible for some (unexpected) behavior. You can use DOM Breakpoints for debugging subtree modifications, attribute modifications or node removal.
Here you can see a very simple example that shows what JavaScript lines are responsible for ...
Unpoly's [up-observe], [up-autosubmit] and [up-validate] as well as their programmatic variants up.observe() and up.autosubmit() are a nightmare for integration tests.
Tests are usually much faster than the configured up.form.config.observeDelay. Therefore, it may happen that you already entered something into the next field before unpoly updates that field with a server response, discarding your changes.
The steps I wait for active ajax requests to complete (if configured) and capybara-lockstep can catch some ...
You have uncommited changes (you can always check by using git status), which you want to discard.
Now there are several options to discard these depending on your exact situation.
The headlines will differentiate the cases whether the files are staged or unstaged.
The robots.txt file and <meta name="robots"> HTML tag can be used to control the behavior of search engine crawlers. Both have different effects.
Marking a URL path as "disallowed" in robots.txt tells crawlers to not access that path.
robots.txt is not a guarantee for exclusion from search engine results.
A "disallowed" URL might be known from an external link, and can still be displayed for a matching search.
Example: even if/adminis disallowed in robots.txt, `/admin/som...
For Rails models where only one of multiple attributes may be filled out at the same time, there is no built-in validation.
I've seen different solutions in the wild, each with different downsides:
validate: works, but is barely portable and clutters the model.Here is a third option: Write a custom validator to ...
Recently we detected a memory leak in one of our applications. Hunting it down, we found that the memory leak was located in Rails' #prepend_view_path. It occurs when the instance method prepend_view_path is called in each request, which is a common thing in a multi-tenant application.
On top of leaking memory, it also causes a performance hit, since templates rendered using the prepended view path will not be cached and compiled anew on each request.
This is not a new memory leak. It was [first reported in in 2014](https://github.com/...
The linked content includes a few design patterns implemented with Ruby on Rails.
What is the card indented to achieve?
Included Design Patterns: Service, Value objec...
You can use the code below to check whether the browser can make connections to the current site:
await isOnline() // resolves to true or false
navigator.onLine
While you can use the built-in function navigator.onLine (sic), it is only a hint for whether the device can access the Internet.
When navigator.onLine === false you know for certain that the user device has no connection to the Internet. This mea...
I recently wanted to add a model for address information but also wanted to add a unique index to those fields that is case-insensitive.
The model looked like this:
create_table :shop_locations do |t|
t.string :street
t.string :house_number
t.string :zip_code
t.string :city
t.belongs_to :shop
end
But how to solve the uniqueness problem?
Another day, another undocumented Rails feature!
This time, it’s that ActiveRecord::Base.connection.add_index supports an undocumented option to pass a string argument as the v...
It might sometimes be useful to check whether your Rails application accesses the file system unnecessarily, for example if your file system access is slow because it goes over the network.
The culprit might be a library like carrierwave that checks file existence or modification times, whereas your application could determine all this from your database.
One option it to use strace for this, which logs all system calls performed by a process.
To do this, start your rails server using something like
DISA...
Testing file download links in an end-to-end test can be painful, especially with Selenium.
The attached download_helpers.rb provides a download_link method for your Capybara tests. It returns a hash describing the download's response:
details = download_link('Download report')
details[:disposition] # => 'attachment' or 'inline'
details[:filename] # => 'report.txt'
details[:text] # => file content as string
details[:content_type] # => 'text/plain'
Compared to [other approaches](...
While verifying doubles in RSpec is a good default, it is limited in the amount of methods it actually is able to verify.
The background is that RSpec can't verify dynamically defined methods, which is a known issue for the usage of helper_method and also the reason why [RSpec >= 3.6](http://rspec.info/blog/2017/05/rspec-3-6-has-been-rel...
tl;dr
You can useattribute?as shorthanded version ofattribute.present?, except for numeric attributes and associations.
attribute? is generated for all attributes and not only for boolean attributes.
These methods are using #query_attribute under the hood. For more details you can see ActiveRecord::AttributeMethods::Query.
In most circumstances query_attribute is working like attribute.present?. If your attribute is responding to :zero? then you have to be aware that `query_attri...
Redis.current will be removed without replacement in redis-rb 5.0.
Version 4.6.0 adds deprecation warnings for Redis.current and Redis.current=:
`Redis.current=` is deprecated and will be removed in 5.0.
If your application still uses Redis.current, you can only fix it by no longer using it. Here is how.
You can easily instantiate a Redis client when you need it.
There is probably already a constant like REDIS_URL that you use to configure Sidekiq or similar. So just use that one.
``...
We use foreman to start all necessary processes for an application, which are declared in a Procfile. This is very convenient, but the outputs of all processes get merged together. Especially while debugging you might not want other processes to flood your screen with their log messages.
The following setup allows you to start Terminator in a split view with the Rails server running in the left pane and all remaining processes running via foreman in the right pane. It was heavily inspired by [this card](https://makandracards.com/makandr...
Building application assets with esbuild is the new way to do it, and it's great, especially in combination with Sprockets (or Propshaft on Rails 7).
You might be missing some convenience features, though.
Here we cover one specific issue:
Once you have started your development Rails server and esbuild with the --watch option (if you used jsbundling-rails to set up, you probably use bin/dev), esbuild will recompile your assets upon change, but build errors will only be printed to the terminal. Your application won't complain about them ...
Attaching files to a field that is handled by Carrierwave uploaders (or maybe any other attachment solution for Rails) in tests allows different approaches. Here is a short summary of the most common methods.
You might also be interested in this card if you see the following error in your test environment:
CarrierWave::FormNotMultipart:
You tried to assign a String or a Pathname to an uploader, for security reasons, this is not allowed.
If this is a file upload, please check that your upload form is multipart encoded.
When Capybara locates elements in the DOM, by default it allows only accessing visible elements -- when you are using a driver that supports it (e.g. Selenium, not the default Rack::Test driver).
Consider the following HTML:
<div class="test1">One<div>
<div class="test2">Two</div>
With some CSS:
.test1 { display: block }
.test2 { display: none }
We will be using Capybara's find below, but this applies to any Capybara finder methods.
visible: :visible or visible: true
As described above, by defa...
Proxy caching is a good feature to serve your publicly visible application content faster and reduce load on your servers. It is e.g. available in nginx, but also affects proxies delivered by ISPs.
Unfortunately, there is a little problem in Rails < 6.1 when delivering responses for different MIME-types. Say you have an arbitrary route in your Rails application that is able to respond with regular HTML and JSON. By sending the specific MIME type in the Accept header, you tell the application to either return HTML (text/html) or JSON (`t...
Rack::SteadyETag is a Rack middleware that generates the same default ETag for responses that only differ in CSRF tokens or CSP nonces.
By default Rails uses Rack::ETag to generate ETag headers by hashing the response body. In theory this would enable caching for multiple requests to the same resourc...
The Interactive Advertising Bureau (IAB) is a European marketing association which has introduced a standard how advertising can be served to users in line with the General Data Protection Regulation (GDPR). This standard is called the TCF 2.0 (Transparency and Consent Framework). If you want to integrate any kind of advertising into a website, chances are the advertising network will require your website to implement that standard. This is a very brief overview of what this means:
The basic idea in the TCF 2.0 ...
Modern versions of Capybara include a finder method #ancestor which allows you to find a parental element using CSS or XPath.
If you previously did something like this:
field.find(:xpath, './ancestor::div[contains(@class, "form-group")]')
..and prefer CSS, you may rewrite it:
field.ancestor('div.form-group')
Both versions will return the outermost matching element. Use the #order option find the closest parent:
field.ancestor('div.form-group', order: :reverse)
A flaky test is a test that is often green, but sometimes red. It may only fail on some PCs, or only when the entire test suite is run.
There are many causes for flaky tests. This card focuses on a specific class of feature with heavy side effects, mostly on on the UI. Features like the following can amplify your flakiness issues by unexpectedly changing elements, causing excessive requests or other timing issues:
Besides their default styling properties, HTML elements have a semantic meaning. For example, an h1 tag is usually styled with a larger font and bold, while it denotes "the single most important headline in its context".
While CSS enables us to style almost any HTML element like anything that is needed, choosing HTML elements corresponding to the meaning of their content has a few advantages: