Switching the currency doesn't work when page_cache or dynamic_page_cache are enabled

We need our own cache context here.

+++ b/commerce_currency_switcher.module
@@ -0,0 +1,16 @@
+  if (array_key_exists('#commerce_product', $build) ||
+      array_key_exists('#commerce_product_variation', $build)) {
+  	// Add our cache context.
...
+    /*if (array_key_exists('variations', $build)) {
...
+    }*/

Why not just !empty($build[''])?

Tab not space.

Commented code.

.

Struggling with my texteditor .. sorry ..

so here we go ..

and finally ..

no more comments

it starts getting scary

But here's the updated patch. Thank you for your suggestions.
As I don't like double negations, I left the array_key_exists.

+1

Side note for another issue: Using the session returned from the request is not as stable as using the normal session service. We experienced a lot of bugs when using this approach.

Join the discussion about the storage here #2914898: Store user's currency in a cookie instead of a session

Last patch doesn't apply cleanly on latest head, so tweaking and committing.

Committed and Thanks @matt, @lukas and @ytsurk.