Fix endcoding/decoding of builtins

[willemneal]

E.g.

ERROR TS2339: Property 'encode' does not exist on type '~lib/string/String'.

               result.encode(encoder, null);
                      ~~~~~~
 in assembly/main.ts(108,21)

[willemneal]

Turns out it does handle strings. The issue was that when I changed the return type of an exported function to string | null then the wrapper no longer saw it as a string since "string" !== "string | null".

This was done because storage.get(key) returns a value or null. So the way I got it to compile was to add do return storage.get(key)! which turns into a runtime check and if the value returned is null it aborts.

The more I think about it the less I like the idea of return null, because internall null is the zero index into the function table, which means that the outside would will just see zero. So I think that it's fair to abort if the return value is null.

@bowenwang1996 @vgrichina Thoughts?

[bowenwang1996]

Which function is this?

[willemneal]

main.ts from near-shell/blank_project:

//@nearfile
import { near, context, storage, logging } from "near-runtime-ts";
import { Greeter } from "./model";

// --- contract code goes below

// It's good to use common constant, but not required.
const LAST_SENDER_KEY = "last_sender";

// This is our change method. It modifies the state of the contract by
// storing the account_id of the sender under the key "last_sender" on the blockchain
export function sayHi(): void {
  // context.sender is the account_id of the user who sent this call to the contract
  // It's provided by the Blockchain runtime. For now we just store it in a local variable.
  let sender = context.sender;
  // `near` class contains some helper functions, e.g. logging.
  // Logs are not persistently stored on the blockchain, but produced by the blockchain runtime.
  // It's helpful to use logs for debugging your functions or when you need to get some info
  // from the change methods (since change methods don't return values to the front-end).
  logging.log(sender + " says \"Hello mate!\"");
  // storage is a helper class that allows contracts to modify the persistent state
  // and read from it. setString allows you to persitently store a string value for a given string key.
  // We'll store the last sender of this contract who called this method.
  storage.setString(LAST_SENDER_KEY, sender);
}

// This is our view method. It returns the last account_id of a sender who called `sayHi`.
// It reads value from the persistent store under the key "last_sender" and returns it.
export function whoSaidHi(): string {
  // getString returns a string value for a given string key.
  return storage.getString(LAST_SENDER_KEY)!;
}

It's the last function, which returns a string and now checks that the string from storage is not null at runtime.

[bowenwang1996]

Yeah I think that's fine. The string should exist and if it does not then the program should abort.

[willemneal]

So should we push this into the storage class or should users have to add the !?

[bowenwang1996]

Users should add !. The storage API is not subject to change at this point

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