feat(examples): refactor grc20 (#2529)

Main changes:
- rename `AdminToken` -> `Banker`
- rename `GRC20` -> `Token`
- remove unused helpers
- remove vault (temporarily, will be reimplemented)
- remove the returner ˋerror` when unnecessary
- use `std.Emit`
- use uassert for testing
- better file naming and organization for improved readability

Fixes #2294
Replaces #2314 (h/t @leohhhn)
~Depends on #2534~
BREAKING CHANGE

---------

Signed-off-by: moul <[email protected]>
Co-authored-by: Leon Hudak <[email protected]>

docs/assets/how-to-guides/creating-grc20/mytoken-1.gno

@@ -1,3 +1,5 @@
+package mytoken
+
 import (
 	"std"
 	"strings"
@@ -7,7 +9,8 @@ import (
 )
 
 var (
-	mytoken *grc20.AdminToken
+	banker  *grc20.Banker
+	mytoken grc20.Token
 	admin   std.Address
 )
 
@@ -17,9 +20,11 @@ func init() {
 	admin = std.PrevRealm().Addr()
 
 	// Set token name, symbol and number of decimals
-	mytoken = grc20.NewAdminToken("My Token", "TKN", 4)
+	banker = grc20.NewBanker("My Token", "TKN", 4)
 
 	// Mint 1 million tokens to admin
-	mytoken.Mint(admin, 1000000*10000)
-}
+	banker.Mint(admin, 1_000_000*10_000) // 1M
 
+	// Get the GRC20 compatible safe object
+	mytoken = banker.Token()
+}

docs/assets/how-to-guides/creating-grc20/mytoken-2.gno

@@ -1,3 +1,12 @@
+package mytoken
+
+import (
+	"std"
+	"strings"
+
+	"gno.land/p/demo/ufmt"
+)
+
 // TotalSupply returns the total supply of mytoken
 func TotalSupply() uint64 {
 	return mytoken.TotalSupply()
@@ -10,84 +19,39 @@ func Decimals() uint {
 
 // BalanceOf returns the balance mytoken for `account`
 func BalanceOf(account std.Address) uint64 {
-	balance, err := mytoken.BalanceOf(account)
-	if err != nil {
-		panic(err)
-	}
-
-	return balance
+	return mytoken.BalanceOf(account)
 }
 
 // Allowance returns the allowance of spender on owner's balance
 func Allowance(owner, spender std.Address) uint64 {
-	allowance, err := mytoken.Allowance(owner, spender)
-	if err != nil {
-		panic(err)
-	}
-
-	return allowance
+	return mytoken.Allowance(owner, spender)
 }
 
 // Transfer transfers amount from caller to recipient
 func Transfer(recipient std.Address, amount uint64) {
-	caller := std.PrevRealm().Addr()
-	if err := mytoken.Transfer(caller, recipient, amount); err != nil {
-		panic(err)
-	}
+	checkErr(mytoken.Transfer(recipient, amount))
 }
 
 // Approve approves amount of caller's tokens to be spent by spender
 func Approve(spender std.Address, amount uint64) {
-	caller := std.PrevRealm().Addr()
-	if err := mytoken.Approve(caller, spender, amount); err != nil {
-		panic(err)
-	}
+	checkErr(mytoken.Approve(spender, amount))
 }
 
 // TransferFrom transfers `amount` of tokens from `from` to `to`
 func TransferFrom(from, to std.Address, amount uint64) {
-	caller := std.PrevRealm().Addr()
-
-	if amount <= 0 {
-		panic("transfer amount must be greater than zero")
-	}
-
-	if err := mytoken.TransferFrom(caller, from, to, amount); err != nil {
-		panic(err)
-	}
+	checkErr(mytoken.TransferFrom(from, to, amount))
 }
 
 // Mint mints amount of tokens to address. Callable only by admin of token
 func Mint(address std.Address, amount uint64) {
 	assertIsAdmin(std.PrevRealm().Addr())
-
-	if amount <= 0 {
-		panic("mint amount must be greater than zero")
-	}
-
-	if err := mytoken.Mint(address, amount); err != nil {
-		panic(err)
-	}
+	checkErr(banker.Mint(address, amount))
 }
 
 // Burn burns amount of tokens from address. Callable only by admin of token
 func Burn(address std.Address, amount uint64) {
 	assertIsAdmin(std.PrevRealm().Addr())
-
-	if amount <= 0 {
-		panic("burn amount must be greater than zero")
-	}
-
-	if err := mytoken.Burn(address, amount); err != nil {
-		panic(err)
-	}
-}
-
-// assertIsAdmin asserts the address is the admin of token
-func assertIsAdmin(address std.Address) {
-	if address != admin {
-		panic("restricted access")
-	}
+	checkErr(banker.Burn(address, amount))
 }
 
 // Render renders the state of the realm
@@ -108,3 +72,17 @@ func Render(path string) string {
 		return "404\n"
 	}
 }
+
+// assertIsAdmin asserts the address is the admin of token
+func assertIsAdmin(address std.Address) {
+	if address != admin {
+		panic("restricted access")
+	}
+}
+
+// checkErr asserts the function didn't returned an error
+func checkErr(err error) {
+	if err != nil {
+		panic(err)
+	}
+}

docs/concepts/effective-gno.md

@@ -701,12 +701,11 @@ best of both worlds, you can wrap a Coins into a GRC20 compatible token.
 ```go
 import "gno.land/p/demo/grc/grc20"
 
-var fooToken grc20.AdminToken = grc20.NewAdminToken("Foo Token", "FOO", 4)
+var fooToken = grc20.NewBanker("Foo Token", "FOO", 4)
 
 func MyBalance() uint64 {
 	caller := std.PrevRealm().Addr()
-	balance, _ := fooToken.BalanceOf(caller)
-	return balance
+	return fooToken.BalanceOf(caller)
 }
 ```
 

docs/concepts/packages.md

@@ -41,12 +41,12 @@ The role of each function is as follows:
 
 Two types of contracts exist in`grc20`:
 
-1. `AdminToken`
+1. `Banker`
    - Implements the token factory with `Helper` functions.
-   - The underlying struct should not be exposed to users. However, it can be typecasted as UserToken using the `GRC20()` method.
-2. `UserToken`
-   - Implements the `IGRC20` interface.
-   - The underlying struct can be exposed to users. Created with the `GRC20()` method of `adminToken`.
+   - The underlying struct should not be exposed to users. However, it can return a typecasted `Token` object using the `Token()` method.
+2. `Token`
+   - Implements the `GRC20` interface.
+   - The underlying struct can be exposed to users. Created with the `Token()` method of `Banker`.
 
 ## `grc721`