RewriteCond exception only single path - apache

Question

I'm setting up htaccess. How to configure it to work like this:
example.com/dir/* → example.com/dir/index.php
example.com/dir/subdir/* → example.com/dir/index.php
example.com/dir/index.html → example.com/dir/ (I want to replace index.php to index.html only in this directory)
example.com/dir/ → example.com/dir/ (I want to see the index.html as content)
There are two different files in dir:
index.php
index.html
I am trying to ensure that these conditions work as before, with the exception of the one directory (example.com/dir/) only:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^ - [L]
RewriteRule ^index\.php$ - [L]
That's how I tried:
DirectoryIndex index.html index.php ## trying to make index.html first
RewriteCond %{REQUEST_URI} ^/dir/
RewriteRule ^index\.html$ - [L]
#
RewriteCond %{REQUEST_FILENAME} -f
RewriteCond %{REQUEST_URI} !^/dir/?$ ## trying to make an exception
RewriteRule ^ - [L]
RewriteRule ^index\.php$ - [L]

Answer 1

I think your approach is much too complicated, unless there are additional restriction you failed to name in the question.
RewriteEngine on
RewriteRule ^/?dir/index\.html$ /dir/ [END]
RewriteRule ^/?dir/ /dir/index.php [END]
One could also understand the remark about the index.html file different:
RewriteEngine on
RewriteRule ^/?dir/(index\.php)?$ /dir/index.html [END]
RewriteRule ^/?dir/ /dir/index.php [END]
In case you receive an internal server error (http status 500) using the rule above then chances are that you operate a very old version of the apache http server. You will see a definite hint to an unsupported [END] flag in your http servers error log file in that case. You can either try to upgrade or use the older [L] flag, but things get more complicated then:
RewriteEngine on
RewriteRule ^/?dir/(index\.php)?$ /dir/index.html [END]
RequestCond %{REQUEST_URI} ^!/dir/index\.html$
RewriteRule ^/?dir/ /dir/index.php [END]
These rules will work likewise in the http servers host configuration or inside a dynamic configuration file (".htaccess" file). Obviously the rewriting module needs to be loaded inside the http server and enabled in the http host. In case you use a dynamic configuration file you need to take care that it's interpretation is enabled at all in the host configuration and that it is located in the host's DOCUMENT_ROOT folder.
And a general remark: you should always prefer to place such rules in the http servers host configuration instead of using dynamic configuration files (".htaccess"). Those dynamic configuration files add complexity, are often a cause of unexpected behavior, hard to debug and they really slow down the http server. They are only provided as a last option for situations where you do not have access to the real http servers host configuration (read: really cheap service providers) or for applications insisting on writing their own rules (which is an obvious security nightmare).