feat(gnovm, tm2): implement event emission with std.Emit (#1653)

# Description

Succeed in my predecessor's legacy.

I have implemented the output to show the path where the event occurred,
as discussed in #1833. Also made it print the timestamp or block height
together.

## Key Changes

In this change, event emission functionality has been added to the Gno.
The main changes include:

1. Introducing of the `emitEvent` function:
- The `emitEvent` function emits an event based on the given type and
attributes
    - Attributes are passed as an even-length of array key-value pairs
- When emitting an event, the current _package path_, _timestamp_, and
_block height_ information are recorded along with the event(discussed
in #1833). This metadata provides additional context about where the
event occured.

2. Additional of event-related types and functions in the `sdk`
packages:
- `NewEvent` creates a new `Event` object based on the provided
information.
- `ArributedEvent` struct contains informations such as event type,
package path, block height, timestamp and attributes. But I'm not sure
how to utilize the `eventType` yet. So, I've just put it as a
placeholder which will be a disscussion for another time.
- `EventArribute` represents an attribute of an event and consists of a
key-value pair
- `NewEventArribute` creates a new `EventAttribute` object based on the
given key-value pair.

## Example

```go
package ee

import (
	"std"
)

const (
	EventSender = "sender"
	EventReceiver = "receiver"
)

func Sender(){
    SubSender()
    SubReceiver()
}

func SubSender() {
    std.Emit(
        EventSender,
		"key1", "value1",
		"key2", "value2",
		"key3", "value3",
    )  
}

func SubReceiver() {
    std.Emit(
        EventReceiver,
        "bar", "baz",
    )
}

func Receiver() {
    std.Emit(
        EventReceiver,
        "foo", "bar",
    )
}
```

### Result

```json
[
  "{\"type\":\"sender\",\"pkg_path\":\"gno.land/r/demo/ee\",\"identifier\":\"SubSender\",\"timestamp\":1713846501,\"attributes\":[{\"key\":\"key1\",\"value\":\"value1\"},{\"key\":\"key2\",\"value\":\"value2\"},{\"key\":\"key3\",\"value\":\"value3\"}]}",
  "{\"type\":\"receiver\",\"pkg_path\":\"gno.land/r/demo/ee\",\"identifier\":\"SubReceiver\",\"timestamp\":1713846501,\"attributes\":[{\"key\":\"bar\",\"value\":\"baz\"}]}"
]
```

## Related Issue/PR

#575 emit & event built-in functions (@r3v4s)
#853 feat: event & emit in gno (@anarcher) <- previous work.
#975 [META] Gno Wishlist / Feature Request Dump (@zivkovicmilos)

---------

Co-authored-by: n3wbie <r3v4@onbloc.xyz>
Co-authored-by: Manfred Touron <94029+moul@users.noreply.github.com>

gno.land/cmd/gnoland/testdata/addpkg.txtar

@@ -1,37 +1,25 @@
 # test for add package
 
+# load hello.gno package located in $WORK directory as gno.land/r/hello
+loadpkg gno.land/r/hello $WORK
+
 ## start a new node
 gnoland start
 
-## add hello.gno package located in $WORK directory as gno.land/r/hello
-gnokey maketx addpkg -pkgdir $WORK -pkgpath gno.land/r/hello -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
-
-## compare AddPkg
-cmp stdout stdout.addpkg.success
-
-
 ## execute SayHello
-gnokey maketx call -pkgpath gno.land/r/hello -func SayHello -gas-fee 1000000ugnot -gas-wanted 2000000  -broadcast -chainid=tendermint_test test1
-
+gnokey maketx call -pkgpath gno.land/r/hello -func SayHello -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
 
 ## compare SayHello
-cmp stdout stdout.call.success
+stdout '\("hello world!" string\)'
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   \d+'
+stdout 'HEIGHT:     \d+'
+stdout 'EVENTS:     \[\]'
 
 -- hello.gno --
 package hello
 
 func SayHello() string {
  	return "hello world!"
 }
-
-
--- stdout.addpkg.success --
-
-OK!
-GAS WANTED: 2000000
-GAS USED:   119829
--- stdout.call.success --
-("hello world!" string)
-OK!
-GAS WANTED: 2000000
-GAS USED:   52801

gno.land/cmd/gnoland/testdata/event.txtar

@@ -0,0 +1,59 @@
+# load the package from $WORK directory
+loadpkg gno.land/r/demo/ee $WORK
+
+# start a new node
+gnoland start
+
+gnokey maketx call -pkgpath gno.land/r/demo/ee -func Foo -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   \d+'
+stdout 'HEIGHT:     \d+'
+stdout 'EVENTS:     \[{\"type\":\"foo\",\"pkg_path\":\"gno.land\/r\/demo\/ee\",\"func\":\"SubFoo\",\"attrs\":\[{\"key\":\"key1\",\"value\":\"value1\"},{\"key\":\"key2\",\"value\":\"value2\"},{\"key\":\"key3\",\"value\":\"value3\"}\]},{\"type\":\"bar\",\"pkg_path\":\"gno.land\/r\/demo\/ee\",\"func\":\"SubBar\",\"attrs\":\[{\"key\":\"bar\",\"value\":\"baz\"}\]}\]'
+
+gnokey maketx call -pkgpath gno.land/r/demo/ee -func Bar -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   \d+'
+stdout 'HEIGHT:     \d+'
+stdout 'EVENTS:     \[{\"type\":\"bar\",\"pkg_path\":\"gno.land\/r\/demo\/ee\",\"func\":\"Bar\",\"attrs\":\[{\"key\":\"foo\",\"value\":\"bar\"}\]}\]'
+
+-- ee.gno --
+package ee
+
+import (
+	"std"
+)
+
+const (
+	EventFoo = "foo"
+	EventBar = "bar"
+)
+
+func Foo(){
+    SubFoo()
+    SubBar()
+}
+
+func SubFoo() {
+    std.Emit(
+        EventFoo,
+		"key1", "value1",
+		"key2", "value2",
+		"key3", "value3",
+    )  
+}
+
+func SubBar() {
+    std.Emit(
+        EventBar,
+        "bar", "baz",
+    )
+}
+
+func Bar() {
+    std.Emit(
+        EventBar,
+        "foo", "bar",
+    )
+}

gno.land/cmd/gnoland/testdata/event_callback.txtar

@@ -0,0 +1,51 @@
+# load the package from $WORK directory
+loadpkg gno.land/r/demo/cbee $WORK
+
+# start a new node
+gnoland start
+
+gnokey maketx call -pkgpath gno.land/r/demo/cbee -func Foo -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   [0-9]+'
+stdout 'HEIGHT:     [0-9]+'
+stdout 'EVENTS:     \[{\"type\":\"foo\",\"pkg_path\":\"gno\.land\/r\/demo\/cbee\",\"func\":\"subFoo\",\"attrs\":\[{\"key\":\"k1\",\"value\":\"v1\"},{\"key\":\"k2\",\"value\":\"v2\"}\]},{\"type\":\"bar\",\"pkg_path\":\"gno\.land\/r\/demo\/cbee\",\"func\":\"subBar\",\"attrs\":\[{\"key\":\"bar\",\"value\":\"baz\"}\]}\]'
+
+
+-- cbee.gno --
+package cbee
+
+import (
+    "std"
+)
+
+const (
+	foo = "foo"
+	bar = "bar"
+)
+
+type contractA struct{}
+
+func (c *contractA) foo(cb func()) {
+	subFoo()
+	cb()
+}
+
+func subFoo() {
+	std.Emit(foo, "k1", "v1", "k2", "v2")
+}
+
+type contractB struct{}
+
+func (c *contractB) subBar() {
+	std.Emit(bar, "bar", "baz")
+}
+
+func Foo() {
+    a := &contractA{}
+	b := &contractB{}
+
+	a.foo(func() {
+		b.subBar()
+	})
+}

gno.land/cmd/gnoland/testdata/event_defer_callback_loop.txtar

@@ -0,0 +1,64 @@
+# load the package from $WORK directory
+loadpkg gno.land/r/demo/edcl $WORK
+
+# start a new node
+gnoland start
+
+gnokey maketx call -pkgpath gno.land/r/demo/edcl -func Main -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   [0-9]+'
+stdout 'HEIGHT:     [0-9]+'
+stdout 'EVENTS:     \[{\"type\":\"ForLoopEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"\",\"attrs\":\[{\"key\":\"iteration\",\"value\":\"0\"},{\"key\":\"key\",\"value\":\"value\"}\]},{\"type\":\"ForLoopEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"\",\"attrs\":\[{\"key\":\"iteration\",\"value\":\"1\"},{\"key\":\"key\",\"value\":\"value\"}\]},{\"type\":\"ForLoopEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"\",\"attrs\":\[{\"key\":\"iteration\",\"value\":\"2\"},{\"key\":\"key\",\"value\":\"value\"}\]},{\"type\":\"ForLoopCompletionEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"forLoopEmitExample\",\"attrs\":\[{\"key\":\"count\",\"value\":\"3\"}\]},{\"type\":\"CallbackEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"\",\"attrs\":\[{\"key\":\"key1\",\"value\":\"value1\"},{\"key\":\"key2\",\"value\":\"value2\"}\]},{\"type\":\"CallbackCompletionEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"callbackEmitExample\",\"attrs\":\[{\"key\":\"key\",\"value\":\"value\"}\]},{\"type\":\"DeferEvent\",\"pkg_path\":\"gno.land\/r\/demo\/edcl\",\"func\":\"deferEmitExample\",\"attrs\":\[{\"key\":\"key1\",\"value\":\"value1\"},{\"key\":\"key2\",\"value\":\"value2\"}\]}\]'
+
+-- edcl.gno --
+
+package edcl
+
+import (
+	"std"
+    "strconv"
+)
+
+func Main() {
+	deferEmitExample()
+}
+
+func deferEmitExample() {
+	defer func() {
+		std.Emit("DeferEvent", "key1", "value1", "key2", "value2")
+		println("Defer emit executed")
+	}()
+
+	forLoopEmitExample(3, func(i int) {
+		std.Emit("ForLoopEvent", "iteration", strconv.Itoa(i), "key", "value")
+	    println("For loop emit executed: iteration ", i)
+	})
+
+	callbackEmitExample(func() {
+		std.Emit("CallbackEvent", "key1", "value1", "key2", "value2")
+		println("Callback emit executed")
+	})
+
+	println("deferEmitExample completed")
+}
+
+func forLoopEmitExample(count int, callback func(int)) {
+	defer func() {
+		std.Emit("ForLoopCompletionEvent", "count", strconv.Itoa(count))
+		println("For loop completion emit executed ", count)
+	}()
+
+	for i := 0; i < count; i++ {
+		callback(i)
+	}
+}
+
+func callbackEmitExample(callback func()) {
+	defer func() {
+		std.Emit("CallbackCompletionEvent", "key", "value")
+		println("Callback completion emit executed")
+	}()
+
+	callback()
+}

gno.land/cmd/gnoland/testdata/event_for_statement.txtar

@@ -0,0 +1,64 @@
+# load the package from $WORK directory
+loadpkg gno.land/r/demo/foree $WORK
+
+# start a new node
+gnoland start
+
+gnokey maketx call -pkgpath gno.land/r/demo/foree -func Foo -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   [0-9]+'
+stdout 'HEIGHT:     [0-9]+'
+stdout 'EVENTS:     \[{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]},{"type":"testing","pkg_path":"gno.land\/r\/demo\/foree","func":"Foo","attrs":\[{"key":"foo","value":"bar"}\]}\]'
+
+gnokey maketx call -pkgpath gno.land/r/demo/foree -func Bar -gas-fee 1000000ugnot -gas-wanted 2000000 -broadcast -chainid=tendermint_test test1
+stdout OK!
+stdout 'GAS WANTED: 2000000'
+stdout 'GAS USED:   [0-9]+'
+stdout 'HEIGHT:     [0-9]+'
+stdout 'EVENTS:     \[{"type":"Foo","pkg_path":"gno.land\/r\/demo\/foree","func":"subFoo","attrs":\[{"key":"k1","value":"v1"},{"key":"k2","value":"v2"}\]},{"type":"Bar","pkg_path":"gno.land\/r\/demo\/foree","func":"subBar","attrs":\[{"key":"bar","value":"baz"}\]},{"type":"Foo","pkg_path":"gno.land\/r\/demo\/foree","func":"subFoo","attrs":\[{"key":"k1","value":"v1"},{"key":"k2","value":"v2"}\]},{"type":"Bar","pkg_path":"gno.land\/r\/demo\/foree","func":"subBar","attrs":\[{"key":"bar","value":"baz"}\]}\]'
+
+
+-- foree.gno --
+
+package foree
+
+import "std"
+
+func Foo() {
+	for i := 0; i < 10; i++ {
+		std.Emit("testing", "foo", "bar")
+	}
+}
+
+const (
+	eventFoo = "Foo"
+	eventBar = "Bar"
+)
+
+type contractA struct{}
+
+func (c *contractA) Foo(cb func()) {
+	subFoo()
+	cb()
+}
+
+func subFoo() {
+	std.Emit(eventFoo, "k1", "v1", "k2", "v2")
+}
+
+type contractB struct{}
+
+func (c *contractB) subBar() {
+	std.Emit(eventBar, "bar", "baz")
+}
+
+func Bar() {
+    a := &contractA{}
+	b := &contractB{}
+	for i := 0; i < 2; i++ {
+		a.Foo(func() {
+			b.subBar()
+		})
+	}
+}

gno.land/pkg/sdk/vm/keeper.go

@@ -186,6 +186,7 @@ func (vm *VMKeeper) AddPackage(ctx sdk.Context, msg MsgAddPackage) (err error) {
 		OrigSendSpent: new(std.Coins),
 		OrigPkgAddr:   pkgAddr.Bech32(),
 		Banker:        NewSDKBanker(vm, ctx),
+		EventLogger:   ctx.EventLogger(),
 	}
 	// Parse and run the files, construct *PV.
 	m2 := gno.NewMachineWithOptions(
@@ -275,6 +276,7 @@ func (vm *VMKeeper) Call(ctx sdk.Context, msg MsgCall) (res string, err error) {
 		OrigSendSpent: new(std.Coins),
 		OrigPkgAddr:   pkgAddr.Bech32(),
 		Banker:        NewSDKBanker(vm, ctx),
+		EventLogger:   ctx.EventLogger(),
 	}
 	// Construct machine and evaluate.
 	m := gno.NewMachineWithOptions(
@@ -351,6 +353,7 @@ func (vm *VMKeeper) Run(ctx sdk.Context, msg MsgRun) (res string, err error) {
 		OrigSendSpent: new(std.Coins),
 		OrigPkgAddr:   pkgAddr.Bech32(),
 		Banker:        NewSDKBanker(vm, ctx),
+		EventLogger:   ctx.EventLogger(),
 	}
 	// Parse and run the files, construct *PV.
 	buf := new(bytes.Buffer)
@@ -500,6 +503,7 @@ func (vm *VMKeeper) QueryEval(ctx sdk.Context, pkgPath string, expr string) (res
 		// OrigSendSpent: nil,
 		OrigPkgAddr: pkgAddr.Bech32(),
 		Banker:      NewSDKBanker(vm, ctx), // safe as long as ctx is a fork to be discarded.
+		EventLogger: ctx.EventLogger(),
 	}
 	m := gno.NewMachineWithOptions(
 		gno.MachineOptions{
@@ -566,6 +570,7 @@ func (vm *VMKeeper) QueryEvalString(ctx sdk.Context, pkgPath string, expr string
 		// OrigSendSpent: nil,
 		OrigPkgAddr: pkgAddr.Bech32(),
 		Banker:      NewSDKBanker(vm, ctx), // safe as long as ctx is a fork to be discarded.
+		EventLogger: ctx.EventLogger(),
 	}
 	m := gno.NewMachineWithOptions(
 		gno.MachineOptions{

gnovm/stdlibs/std/context.go

@@ -17,4 +17,5 @@ type ExecContext struct {
 	OrigSend      std.Coins
 	OrigSendSpent *std.Coins // mutable
 	Banker        BankerInterface
+	EventLogger   *sdk.EventLogger
 }

gnovm/stdlibs/std/emit_event.gno

@@ -0,0 +1,19 @@
+package std
+
+// Emit is a function that constructs a gnoEvent with a specified type and attributes.
+// It then forwards this event to the event logger. Each emitted event carries metadata
+// such as the event type, the initializing realm, and the provided attributes.
+//
+// The function takes type and attribute strings. typ (or type) is an arbitrary string that represents
+// the type of the event. It plays a role of indexing what kind of event occurred. For example,
+// a name like "Foo" or "Bar" can be used to indicating the purpose (nature) of the event.
+//
+// And the attrs (attributes) accepts an even number of strings and sets them as key-value pairs
+// according to the order they are passed. For example, if the attr strings "key1", "value1" are
+// passed in, the key is set to "key1" and the value is set to "value1".
+//
+// The event is dispatched to the EventLogger, which resides in the tm2/pkg/sdk/events.go file.
+//
+// For more details about the GnoEvent data structure, refer to its definition in the emit_event.go file.
+func Emit(typ string, attrs ...string) { emit(typ, attrs) }
+func emit(typ string, attrs []string)