Add metadata information to generated .abi.json file (master-2.x)

[devhawk]

Fixes #144

This PR adds a new "metadata" property to the .abi.json file generated by NEON (2.x branch). It contains the metadata needed by Neo.Contract.Create to deploy contracts that can't be obtained from the AVM or existing .abi.json file.

Having this information included in the abi.json file enables tools like neo-express and neo-visual-devtracker to deploy contracts w/o collecting this information from the developer at contract deployment time. Additionally, by specifying these values in source (as per below), we also reduce the potential for errors at contract deployment time.

The contract metadata can be included in the contract C# source code via a set of new custom attributes that this PR adds to the Neo.SmartContract.Framework package.

using Neo.SmartContract.Framework;

[assembly: ContractTitle("MyTestContract")]
[assembly: ContractDescription("This is the description of my contract")]
[assembly: ContractVersion("2.0")]
[assembly: ContractAuthor("DevHawk")]
[assembly: ContractEmail("devhawk@outlook.com")]
[assembly: ContractHasStorage]

// can also specify a contract can be dynamically invoked or is payable
// [assembly: ContractHasDynamicInvoke]
// [assembly: ContractIsPayable]

The resulting metadata node looks in the contract.abi.json file looks like this:

"metadata":
{
    "title":"MyTestContract",
    "description":"This is a description of my contract",
    "version":"2.0",
    "author":"DevHawk",
    "email":"devhawk@outlook.com",
    "has-storage":true,
    "has-dynamic-invoke":false,
    "is-payable":false
},

NEON uses the following defaults if metadata is not specified via custom attributes:

• Contract title defaults to the AssemblyDef.Name.Name field defined in metadata.
• Contract version defaults to the AssemblyDef.Name.Version field defined in metadata
• Remaining string properties default to empty string
• Boolean properties default to false

The .NET library already has AssemblyTitleAttribute and AssemblyDescriptionAttribute custom attributes. If these attributes are specified, NEON will use them for contract title and description respectively. However, if both standard and Neo contract attributes are used to specify the same metadata, NEON will use the value from the Neo contract attribute.

[lock9]

Changes are fine and you add UT.
Let's wait for the testing team before approving it.

[devhawk]

@superboyiii Can you take a quick look at this PR from a testing perspective?

[lightszero]

agree

[superboyiii]

@superboyiii Can you take a quick look at this PR from a testing perspective?

Sure, @nicolegys will give a quick response of test result.

[nicolegys]

Test:

I added the attributes in my contract and the metadata infomation could be seen in the generated .abi.json file.

Contract code:

.abi.json file:

Now I could not make further test, because this part in neo-cli hasn't been changed.

In addtion, could you also add paramTypes and returnTypeHexString? Or they can be calculated automaticly from the smart contract code.

[devhawk]

Thanks for verifying my PR @nicolegys!

I didn't include the hex string for parameter/return types because it's trivial to parse that information from existing data in the in the .abi.json file.

[shargon]

What's happend if there the value it's null? maybe we should avoid the entry

[devhawk]

The metadata properties being inserted into .abi.json file here all have default values if not specified via custom attributes.