template: speedup lexer (#1335)

* template: add parse benchmarks

Taken from the yagpdb-cc repository. To avoid licensing issues, I only used
programs written by me.

Baseline performance:

name                 time/op
Parse/lorem_ipsum-4  2.01µs ± 7%
Parse/short-4        70.2µs ± 1%
Parse/medium-4        165µs ± 1%
Parse/long-4          517µs ± 1%
Parse/very-long-4    1.79ms ± 1%

name                 alloc/op
Parse/lorem_ipsum-4  1.23kB ± 0%
Parse/short-4        5.48kB ± 0%
Parse/medium-4       12.7kB ± 0%
Parse/long-4         35.3kB ± 0%
Parse/very-long-4     113kB ± 0%

name                 allocs/op
Parse/lorem_ipsum-4    12.0 ± 0%
Parse/short-4           109 ± 0%
Parse/medium-4          298 ± 0%
Parse/long-4            779 ± 0%
Parse/very-long-4     2.61k ± 0%

* template: port upstream changes

Notably, this includes https://go-review.googlesource.com/c/go/+/421883,
which changes the lexer to not spawn a new goroutine.

name                 old time/op    new time/op    delta
Parse/lorem_ipsum-4    2.01µs ± 7%    0.73µs ± 2%  -63.56%  (p=0.000 n=7+8)
Parse/short-4          70.2µs ± 1%    16.6µs ± 1%  -76.32%  (p=0.000 n=7+8)
Parse/medium-4          165µs ± 1%      40µs ± 1%  -75.74%  (p=0.000 n=8+8)
Parse/long-4            517µs ± 1%     123µs ± 1%  -76.28%  (p=0.000 n=8+7)
Parse/very-long-4      1.79ms ± 1%    0.42ms ± 1%  -76.81%  (p=0.000 n=8+8)

name                 old alloc/op   new alloc/op   delta
Parse/lorem_ipsum-4    1.23kB ± 0%    1.16kB ± 0%   -5.56%  (p=0.000 n=8+8)
Parse/short-4          5.48kB ± 0%    5.42kB ± 0%   -1.17%  (p=0.000 n=8+8)
Parse/medium-4         12.7kB ± 0%    12.6kB ± 0%   -0.51%  (p=0.000 n=8+8)
Parse/long-4           35.3kB ± 0%    35.3kB ± 0%   -0.17%  (p=0.000 n=8+8)
Parse/very-long-4       113kB ± 0%     113kB ± 0%   -0.05%  (p=0.000 n=8+8)

name                 old allocs/op  new allocs/op  delta
Parse/lorem_ipsum-4      12.0 ± 0%      10.0 ± 0%  -16.67%  (p=0.000 n=8+8)
Parse/short-4             109 ± 0%       107 ± 0%   -1.83%  (p=0.000 n=8+8)
Parse/medium-4            298 ± 0%       296 ± 0%   -0.67%  (p=0.000 n=8+8)
Parse/long-4              779 ± 0%       777 ± 0%   -0.26%  (p=0.000 n=8+8)
Parse/very-long-4       2.61k ± 0%     2.61k ± 0%   -0.08%  (p=0.000 n=8+8)

* template: add ASCII fast path for lexer.next

lexer.next is a hot function, as demonstrated by profiling. Most programs
will consist of ASCII characters only, which we can optimize for. Ideally
DecodeRuneInString would be inlined here and this wouldn't be a problem at all,
but that won't be the case until golang/go#31666
is resolved.

name                 old time/op    new time/op    delta
Parse/lorem_ipsum-4     733ns ± 2%     733ns ± 2%    ~     (p=0.933 n=8+8)
Parse/short-4          16.6µs ± 1%    15.5µs ± 2%  -6.75%  (p=0.000 n=8+8)
Parse/medium-4         40.1µs ± 1%    38.7µs ± 1%  -3.51%  (p=0.000 n=8+8)
Parse/long-4            123µs ± 1%     115µs ± 1%  -5.86%  (p=0.001 n=7+7)
Parse/very-long-4       416µs ± 1%     396µs ± 1%  -4.70%  (p=0.000 n=8+8)

name                 old alloc/op   new alloc/op   delta
Parse/lorem_ipsum-4    1.16kB ± 0%    1.16kB ± 0%    ~     (all equal)
Parse/short-4          5.42kB ± 0%    5.42kB ± 0%    ~     (all equal)
Parse/medium-4         12.6kB ± 0%    12.6kB ± 0%    ~     (all equal)
Parse/long-4           35.3kB ± 0%    35.3kB ± 0%    ~     (all equal)
Parse/very-long-4       113kB ± 0%     113kB ± 0%    ~     (all equal)

name                 old allocs/op  new allocs/op  delta
Parse/lorem_ipsum-4      10.0 ± 0%      10.0 ± 0%    ~     (all equal)
Parse/short-4             107 ± 0%       107 ± 0%    ~     (all equal)
Parse/medium-4            296 ± 0%       296 ± 0%    ~     (all equal)
Parse/long-4              777 ± 0%       777 ± 0%    ~     (all equal)
Parse/very-long-4       2.61k ± 0%     2.61k ± 0%    ~     (all equal)

* template: preallocate for 4 args in CommandNode

CommandNode.append and by extension runtime.growslice was showing up
more than expected during profiling. Allocate enough space for four
arguments up front so we don't need to reallocate as much. Although
this doesn't benefit performance much, it does have a clear positive effect on
memory usage.

name                 old time/op    new time/op    delta
Parse/lorem_ipsum-4     733ns ± 2%     728ns ± 2%     ~     (p=0.315 n=8+8)
Parse/short-4          15.5µs ± 2%    15.2µs ± 1%   -2.12%  (p=0.001 n=8+8)
Parse/medium-4         38.7µs ± 1%    38.0µs ± 1%   -1.99%  (p=0.000 n=8+8)
Parse/long-4            115µs ± 1%     117µs ± 5%     ~     (p=0.281 n=7+8)
Parse/very-long-4       396µs ± 1%     400µs ± 1%   +1.02%  (p=0.002 n=8+8)

name                 old alloc/op   new alloc/op   delta
Parse/lorem_ipsum-4    1.16kB ± 0%    1.16kB ± 0%     ~     (all equal)
Parse/short-4          5.42kB ± 0%    5.08kB ± 0%   -6.20%  (p=0.000 n=8+8)
Parse/medium-4         12.6kB ± 0%    12.7kB ± 0%   +0.51%  (p=0.000 n=8+8)
Parse/long-4           35.3kB ± 0%    34.4kB ± 0%   -2.58%  (p=0.000 n=8+8)
Parse/very-long-4       113kB ± 0%     110kB ± 0%   -2.37%  (p=0.000 n=8+8)

name                 old allocs/op  new allocs/op  delta
Parse/lorem_ipsum-4      10.0 ± 0%      10.0 ± 0%     ~     (all equal)
Parse/short-4             107 ± 0%        93 ± 0%  -13.08%  (p=0.000 n=8+8)
Parse/medium-4            296 ± 0%       276 ± 0%   -6.76%  (p=0.000 n=8+8)
Parse/long-4              777 ± 0%       705 ± 0%   -9.27%  (p=0.000 n=8+8)
Parse/very-long-4       2.61k ± 0%     2.35k ± 0%   -9.77%  (p=0.000 n=8+8)

lib/template/parse/lex_test.go

@@ -372,7 +372,6 @@ var lexTests = []lexTest{
 	{"extra right paren", "{{3)}}", []item{
 		tLeft,
 		mkItem(itemNumber, "3"),
-		tRpar,
 		mkItem(itemError, `unexpected right paren U+0029 ')'`),
 	}},
 
@@ -543,22 +542,6 @@ func TestPos(t *testing.T) {
 	}
 }
 
-// Test that an error shuts down the lexing goroutine.
-func TestShutdown(t *testing.T) {
-	// We need to duplicate template.Parse here to hold on to the lexer.
-	const text = "erroneous{{define}}{{else}}1234"
-	lexer := lex("foo", text, "{{", "}}")
-	_, err := New("root").parseLexer(lexer)
-	if err == nil {
-		t.Fatalf("expected error")
-	}
-	// The error should have drained the input. Therefore, the lexer should be shut down.
-	token, ok := <-lexer.items
-	if ok {
-		t.Fatalf("input was not drained; got %v", token)
-	}
-}
-
 // parseLexer is a local version of parse that lets us pass in the lexer instead of building it.
 // We expect an error, so the tree set and funcs list are explicitly nil.
 func (t *Tree) parseLexer(lex *lexer) (tree *Tree, err error) {

lib/template/parse/node.go

@@ -247,7 +247,7 @@ type CommandNode struct {
 }
 
 func (t *Tree) newCommand(pos Pos) *CommandNode {
-	return &CommandNode{tr: t, NodeType: NodeCommand, Pos: pos}
+	return &CommandNode{tr: t, NodeType: NodeCommand, Pos: pos, Args: make([]Node, 0, 4)}
 }
 
 func (c *CommandNode) append(arg Node) {

lib/template/parse/parse.go

@@ -195,7 +195,6 @@ func (t *Tree) recover(errp *error) {
 			panic(e)
 		}
 		if t != nil {
-			t.lex.drain()
 			t.stopParse()
 		}
 		*errp = e.(error)

lib/template/parse/parse_test.go

@@ -7,6 +7,8 @@ package parse
 import (
 	"flag"
 	"fmt"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 )
@@ -461,7 +463,7 @@ var errorTests = []parseTest{
 		hasError, `unclosed left paren`},
 	{"rparen",
 		"{{.X 1 2 3)}}",
-		hasError, `unexpected ")"`},
+		hasError, `unexpected right paren`},
 	{"space",
 		"{{`x`3}}",
 		hasError, `in operand`},
@@ -589,12 +591,211 @@ func TestLineNum(t *testing.T) {
 	}
 }
 
-func BenchmarkParseLarge(b *testing.B) {
-	text := strings.Repeat("{{1234}}\n", 10000)
-	for i := 0; i < b.N; i++ {
-		_, err := New("bench").Parse(text, "", "", make(map[string]*Tree), builtins)
+func BenchmarkParse(b *testing.B) {
+	benchmarks := []struct {
+		name, file string
+	}{
+		{"lorem ipsum", "lorem.tmpl"},
+		{"short", "short.tmpl"},
+		{"medium", "medium.tmpl"},
+		{"long", "long.tmpl"},
+		{"very-long", "very_long.tmpl"},
+	}
+	for _, bm := range benchmarks {
+		f, err := os.ReadFile(filepath.Join("..", "testdata", bm.file))
 		if err != nil {
 			b.Fatal(err)
 		}
+
+		in := string(f)
+		b.Run(bm.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				_, err := Parse(bm.name, in, "{{", "}}", funcs)
+				if err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
 	}
 }
+
+var funcs = map[string]interface{}{
+	"add":                       func() interface{} { return nil },
+	"addMessageReactions":       func() interface{} { return nil },
+	"addReactions":              func() interface{} { return nil },
+	"addResponseReactions":      func() interface{} { return nil },
+	"addRoleID":                 func() interface{} { return nil },
+	"addRoleName":               func() interface{} { return nil },
+	"adjective":                 func() interface{} { return nil },
+	"and":                       func() interface{} { return nil },
+	"bitwiseAnd":                func() interface{} { return nil },
+	"bitwiseAndNot":             func() interface{} { return nil },
+	"bitwiseLeftShift":          func() interface{} { return nil },
+	"bitwiseNot":                func() interface{} { return nil },
+	"bitwiseOr":                 func() interface{} { return nil },
+	"bitwiseRightShift":         func() interface{} { return nil },
+	"bitwiseXor":                func() interface{} { return nil },
+	"call":                      func() interface{} { return nil },
+	"cancelScheduledUniqueCC":   func() interface{} { return nil },
+	"carg":                      func() interface{} { return nil },
+	"cbrt":                      func() interface{} { return nil },
+	"cembed":                    func() interface{} { return nil },
+	"complexMessage":            func() interface{} { return nil },
+	"complexMessageEdit":        func() interface{} { return nil },
+	"createTicket":              func() interface{} { return nil },
+	"cslice":                    func() interface{} { return nil },
+	"currentTime":               func() interface{} { return nil },
+	"currentUserAgeHuman":       func() interface{} { return nil },
+	"currentUserAgeMinutes":     func() interface{} { return nil },
+	"currentUserCreated":        func() interface{} { return nil },
+	"dbBottomEntries":           func() interface{} { return nil },
+	"dbCount":                   func() interface{} { return nil },
+	"dbDel":                     func() interface{} { return nil },
+	"dbDelByID":                 func() interface{} { return nil },
+	"dbDelById":                 func() interface{} { return nil },
+	"dbDelMultiple":             func() interface{} { return nil },
+	"dbGet":                     func() interface{} { return nil },
+	"dbGetPattern":              func() interface{} { return nil },
+	"dbGetPatternReverse":       func() interface{} { return nil },
+	"dbIncr":                    func() interface{} { return nil },
+	"dbRank":                    func() interface{} { return nil },
+	"dbSet":                     func() interface{} { return nil },
+	"dbSetExpire":               func() interface{} { return nil },
+	"dbTopEntries":              func() interface{} { return nil },
+	"deleteAllMessageReactions": func() interface{} { return nil },
+	"deleteMessage":             func() interface{} { return nil },
+	"deleteMessageReaction":     func() interface{} { return nil },
+	"deleteResponse":            func() interface{} { return nil },
+	"deleteTrigger":             func() interface{} { return nil },
+	"dict":                      func() interface{} { return nil },
+	"div":                       func() interface{} { return nil },
+	"editChannelName":           func() interface{} { return nil },
+	"editChannelTopic":          func() interface{} { return nil },
+	"editMessage":               func() interface{} { return nil },
+	"editMessageNoEscape":       func() interface{} { return nil },
+	"editNickname":              func() interface{} { return nil },
+	"eq":                        func() interface{} { return nil },
+	"exec":                      func() interface{} { return nil },
+	"execAdmin":                 func() interface{} { return nil },
+	"execCC":                    func() interface{} { return nil },
+	"execTemplate":              func() interface{} { return nil },
+	"fdiv":                      func() interface{} { return nil },
+	"formatTime":                func() interface{} { return nil },
+	"ge":                        func() interface{} { return nil },
+	"getChannel":                func() interface{} { return nil },
+	"getChannelOrThread":        func() interface{} { return nil },
+	"getMember":                 func() interface{} { return nil },
+	"getMessage":                func() interface{} { return nil },
+	"getPinCount":               func() interface{} { return nil },
+	"getRole":                   func() interface{} { return nil },
+	"getTargetPermissionsIn":    func() interface{} { return nil },
+	"getThread":                 func() interface{} { return nil },
+	"giveRoleID":                func() interface{} { return nil },
+	"giveRoleName":              func() interface{} { return nil },
+	"gt":                        func() interface{} { return nil },
+	"hasPermissions":            func() interface{} { return nil },
+	"hasPrefix":                 func() interface{} { return nil },
+	"hasRoleID":                 func() interface{} { return nil },
+	"hasRoleName":               func() interface{} { return nil },
+	"hasSuffix":                 func() interface{} { return nil },
+	"html":                      func() interface{} { return nil },
+	"humanizeDurationHours":     func() interface{} { return nil },
+	"humanizeDurationMinutes":   func() interface{} { return nil },
+	"humanizeDurationSeconds":   func() interface{} { return nil },
+	"humanizeThousands":         func() interface{} { return nil },
+	"humanizeTimeSinceDays":     func() interface{} { return nil },
+	"in":                        func() interface{} { return nil },
+	"inFold":                    func() interface{} { return nil },
+	"index":                     func() interface{} { return nil },
+	"joinStr":                   func() interface{} { return nil },
+	"js":                        func() interface{} { return nil },
+	"json":                      func() interface{} { return nil },
+	"kindOf":                    func() interface{} { return nil },
+	"le":                        func() interface{} { return nil },
+	"len":                       func() interface{} { return nil },
+	"loadLocation":              func() interface{} { return nil },
+	"log":                       func() interface{} { return nil },
+	"lower":                     func() interface{} { return nil },
+	"lt":                        func() interface{} { return nil },
+	"mathConst":                 func() interface{} { return nil },
+	"max":                       func() interface{} { return nil },
+	"mentionEveryone":           func() interface{} { return nil },
+	"mentionHere":               func() interface{} { return nil },
+	"mentionRoleID":             func() interface{} { return nil },
+	"mentionRoleName":           func() interface{} { return nil },
+	"min":                       func() interface{} { return nil },
+	"mod":                       func() interface{} { return nil },
+	"mult":                      func() interface{} { return nil },
+	"ne":                        func() interface{} { return nil },
+	"newDate":                   func() interface{} { return nil },
+	"not":                       func() interface{} { return nil },
+	"noun":                      func() interface{} { return nil },
+	"onlineCount":               func() interface{} { return nil },
+	"onlineCountBots":           func() interface{} { return nil },
+	"or":                        func() interface{} { return nil },
+	"parseArgs":                 func() interface{} { return nil },
+	"pastNicknames":             func() interface{} { return nil },
+	"pastUsernames":             func() interface{} { return nil },
+	"pinMessage":                func() interface{} { return nil },
+	"pow":                       func() interface{} { return nil },
+	"print":                     func() interface{} { return nil },
+	"printf":                    func() interface{} { return nil },
+	"println":                   func() interface{} { return nil },
+	"randInt":                   func() interface{} { return nil },
+	"reFind":                    func() interface{} { return nil },
+	"reFindAll":                 func() interface{} { return nil },
+	"reFindAllSubmatches":       func() interface{} { return nil },
+	"reQuoteMeta":               func() interface{} { return nil },
+	"reReplace":                 func() interface{} { return nil },
+	"reSplit":                   func() interface{} { return nil },
+	"removeRoleID":              func() interface{} { return nil },
+	"removeRoleName":            func() interface{} { return nil },
+	"roleAbove":                 func() interface{} { return nil },
+	"round":                     func() interface{} { return nil },
+	"roundCeil":                 func() interface{} { return nil },
+	"roundEven":                 func() interface{} { return nil },
+	"roundFloor":                func() interface{} { return nil },
+	"scheduleUniqueCC":          func() interface{} { return nil },
+	"sdict":                     func() interface{} { return nil },
+	"sendDM":                    func() interface{} { return nil },
+	"sendMessage":               func() interface{} { return nil },
+	"sendMessageNoEscape":       func() interface{} { return nil },
+	"sendMessageNoEscapeRetID":  func() interface{} { return nil },
+	"sendMessageRetID":          func() interface{} { return nil },
+	"sendTemplate":              func() interface{} { return nil },
+	"sendTemplateDM":            func() interface{} { return nil },
+	"seq":                       func() interface{} { return nil },
+	"setRoles":                  func() interface{} { return nil },
+	"shuffle":                   func() interface{} { return nil },
+	"sleep":                     func() interface{} { return nil },
+	"slice":                     func() interface{} { return nil },
+	"snowflakeToTime":           func() interface{} { return nil },
+	"sort":                      func() interface{} { return nil },
+	"split":                     func() interface{} { return nil },
+	"sqrt":                      func() interface{} { return nil },
+	"str":                       func() interface{} { return nil },
+	"structToSdict":             func() interface{} { return nil },
+	"sub":                       func() interface{} { return nil },
+	"takeRoleID":                func() interface{} { return nil },
+	"takeRoleName":              func() interface{} { return nil },
+	"targetHasPermissions":      func() interface{} { return nil },
+	"targetHasRoleID":           func() interface{} { return nil },
+	"targetHasRoleName":         func() interface{} { return nil },
+	"title":                     func() interface{} { return nil },
+	"toByte":                    func() interface{} { return nil },
+	"toDuration":                func() interface{} { return nil },
+	"toFloat":                   func() interface{} { return nil },
+	"toInt":                     func() interface{} { return nil },
+	"toInt64":                   func() interface{} { return nil },
+	"toRune":                    func() interface{} { return nil },
+	"toString":                  func() interface{} { return nil },
+	"trimSpace":                 func() interface{} { return nil },
+	"unpinMessage":              func() interface{} { return nil },
+	"upper":                     func() interface{} { return nil },
+	"urlescape":                 func() interface{} { return nil },
+	"urlquery":                  func() interface{} { return nil },
+	"urlunescape":               func() interface{} { return nil },
+	"userArg":                   func() interface{} { return nil },
+	"verb":                      func() interface{} { return nil },
+	"weekNumber":                func() interface{} { return nil },
+}

lib/template/testdata/long.tmpl

@@ -0,0 +1,66 @@
+{{/*
+	Views information about the server.
+	See <https://yagpdb-cc.github.io/info/server> for more information.
+
+	Author: jo3-l <https://github.com/jo3-l>
+*/}}
+
+{{ $icon := "" }}
+{{ $name := printf "%s (%d)" .Guild.Name .Guild.ID }}
+{{ if .Guild.Icon }}
+	{{ $ext := "webp" }}
+	{{ if eq (slice .Guild.Icon 0 2) "a_" }} {{ $ext = "gif" }} {{ end }}
+	{{ $icon = printf "https://cdn.discordapp.com/icons/%d/%s.%s" .Guild.ID .Guild.Icon $ext }}
+{{ end }}
+
+{{ $owner := userArg .Guild.OwnerID }}
+{{ $levels := cslice
+	"None: Unrestricted"
+	"Low: Must have a verified email on their Discord account."
+	"Medium: Must also be registered on Discord for longer than 5 minutes."
+	"(╯°□°）╯︵ ┻━┻: Must also be a member of this server for longer than 10 minutes."
+	"┻━┻ ﾐヽ(ಠ益ಠ)ノ彡┻━┻: Must have a verified phone on their Discord account."
+}}
+{{ $afk := "n/a" }}
+{{ if .Guild.AfkChannelID }}
+	{{ $afk = printf "**Channel:** <#%d> (%d)\n**Timeout:** %s"
+		.Guild.AfkChannelID
+		.Guild.AfkChannelID
+		(humanizeDurationSeconds (toDuration (mult .Guild.AfkTimeout .TimeSecond)))
+	}}
+{{ end }}
+{{ $embedsEnabled := "No" }}
+{{ if .Guild.WidgetEnabled }} {{ $embedsEnabled = "Yes" }} {{ end }}
+{{ $createdAt := div .Guild.ID 4194304 | add 1420070400000 | mult 1000000 | toDuration | (newDate 1970 1 1 0 0 0).Add }}
+
+{{ $infoEmbed := cembed
+	"author" (sdict "name" $name "icon_url" $icon)
+	"color" 14232643
+	"thumbnail" (sdict "url" $icon)
+	"fields" (cslice
+		(sdict "name" "Verification Level" "value" (index $levels .Guild.VerificationLevel))
+		(sdict "name" "Region" "value" .Guild.Region)
+		(sdict "name" "Members" "value" (printf "**• Total:** %d Members\n**• Online:** %d Members" .Guild.MemberCount onlineCount))
+		(sdict "name" "Roles" "value" (printf "**• Total:** %d\nUse `-listroles` to list all roles." (len .Guild.Roles)))
+		(sdict "name" "Owner" "value" (printf "%s (%d)" $owner.String $owner.ID))
+		(sdict "name" "AFK" "value" $afk)
+		(sdict "name" "Embeds Enabled" "value" $embedsEnabled)
+	)
+	"footer" (sdict "text" "Created at")
+	"timestamp" $createdAt
+}}
+
+{{ if .CmdArgs }}
+	{{ if eq (index .CmdArgs 0) "icon" }}
+		{{ sendMessage nil (cembed
+			"author" (sdict "name" $name "icon_url" $icon)
+			"title" "Server Icon"
+			"color" 14232643
+			"image" (sdict "url" $icon)
+		) }}
+	{{ else }}
+		{{ sendMessage nil $infoEmbed }}
+	{{ end }}
+{{ else }}
+	{{ sendMessage nil $infoEmbed }}
+{{ end }}

lib/template/testdata/lorem.tmpl

@@ -0,0 +1,3 @@
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.

lib/template/testdata/medium.tmpl

@@ -0,0 +1,30 @@
+{{/*
+	Separates predefined flags from positional arguments within input.
+	See <https://yagpdb-cc.github.io/code-snippets/parse-flags> for more information.
+
+	Licensed under the terms of the Unlicense.
+	Author: jo3-l <https://github.com/jo3-l>
+*/}}
+
+{{define "parseFlags"}}
+	{{.Set "Out" (sdict
+		"Positional" (cslice)
+		"Flags" (dict)
+		"Switches" (dict)
+	)}}
+
+	{{$curFlag := ""}}
+	{{$lastIdx := sub (len .Args) 1}}
+	{{range $i, $arg := .Args}}
+		{{- if $curFlag}}
+			{{- $.Out.Flags.Set $curFlag $arg}}
+			{{- $curFlag = ""}}
+		{{- else if and ($id := $.Flags.Get $arg) (ne $i $lastIdx)}}
+			{{- $curFlag = $id}}
+		{{- else if $id := $.Switches.Get $arg}}
+			{{- $.Out.Switches.Set $id true}}
+		{{- else}}
+			{{- $.Out.Set "Positional" ($.Out.Positional.Append $arg)}}
+		{{- end -}}
+	{{end}}
+{{end}}

lib/template/testdata/short.tmpl

@@ -0,0 +1,15 @@
+{{/*
+	Displays a random color.
+	See <https://yagpdb-cc.github.io/utilities/random-color> for more information.
+
+	Author: jo3-l <https://github.com/jo3-l>
+*/}}
+
+{{ $dec := randInt 0 16777216 }}
+{{ $hex := printf "%06x" $dec }}
+{{ sendMessage nil (cembed
+	"title" "Random Color"
+	"color" $dec
+	"description" (printf "**Decimal:** %d\n**Hex:** #%s" $dec $hex)
+	"thumbnail" (sdict "url" (printf "https://dummyimage.com/400x400/%s/%s" $hex $hex))
+) }}