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Here is how you could set up hot reloading with webpack-encore in a Symfony project.

1. Step one:

Different containers need to be on the same Compose network to communicate. If a service doesn't have a networks: block, Compose automatically attaches it to a default network. So in your example, the server-a container is only on the backend network, but the mongo_db container is only on the default network, and that's why they can't communicate.

The easiest way to resolve this is to delete all of the networks: blocks in the file. Then Compose will attach all of the containers to the default network. Removing other unnecessary options, you could reduce this Compose file to just

These lines should be outside of the structs (Person, Company):

In Solidity doesn't exist the concept of 'NULL' like in C++,C#,Java,... The documentation say this:

The concept of “undefined” or “null” values does not exist in Solidity, but newly declared variables always have a default value dependent on its type. To handle any unexpected values, you should use the revert function to revert the whole transaction, or return a tuple with a second bool value denoting success.

I recommend you to read documentation's section about declarations:

A variable which is declared will have an initial default value whose byte-representation is all zeros. The “default values” of variables are the typical “zero-state” of whatever the type is. For example, the default value for a bool is false. The default value for the uint or int types is 0. For statically-sized arrays and bytes1 to bytes32, each individual element will be initialized to the default value corresponding to its type. For dynamically-sized arrays, bytes and string, the default value is an empty array or string. For the enum type, the default value is its first member.

More information here.

Visibility (public / internal) is not needed for constructors anymore: To prevent a contract from being created, it can be marked abstract. This makes the visibility concept for constructors obsolete.

Source: https://docs.soliditylang.org/en/v0.8.13/070-breaking-changes.html#functions-and-events

So, if you're compiling your contract with Solidity version 0.7 or newer, the constructor visibility (in your case public) is ignored, and you can safely remove it.

For my version of this error, the issue seemed to be that I was importing a file with an alias in webpack from within the same directory.

To give an example, I had this directory setup:

You need to make sure these points:

1. Your Metamask extension is connecting to your hardhat localhost network.
   When you run your React app in a browser with the Metamask extension installed, make sure that your Metamask is connecting to your hardhat localhost network (by default, it is localhost:8545). If Metamask is connecting to a different network, you will get that error.
   (Note: Because the Metamask extension hides test networks by default, you will need to make it show test networks so that you can see your hardhat localhost network listed.)

2. Use the correct contract address.
   When you start a hardhat local network, hardhat will return a list of accounts like this:

I have not enough reputation to just comment so it will be an anwer. Your code is correct but there are may be some tricky issues.

1. The first "false" is the default value as bool is "value type". Read the first paragraph from here.
2. I would reccomend you use remix ide itself (online version for example). I guess different ide extensions can not be fully trusted.
3. You may merely had not waited for transaction to be confirmed so you read old value.

You missed adding this in your eslint.json file.