usage: count parsed files including TS files

This both allows us to figure out if users are using k6 with a lot of
files and if ts support is actually used.

js/bundle.go

@@ -285,6 +285,7 @@ func (bi *BundleInstance) manipulateOptions(options lib.Options) error {
 
 func (b *Bundle) newCompiler(logger logrus.FieldLogger) *compiler.Compiler {
 	c := compiler.New(logger)
+	c.WithUsage(b.preInitState.Usage)
 	c.Options = compiler.Options{
 		CompatibilityMode: b.CompatibilityMode,
 		SourceMapLoader:   generateSourceMapLoader(logger, b.filesystems),

js/compiler/compiler.go

@@ -16,17 +16,30 @@ import (
 	"github.com/sirupsen/logrus"
 
 	"go.k6.io/k6/lib"
+	"go.k6.io/k6/usage"
 )
 
 // A Compiler compiles JavaScript or TypeScript source code into a sobek.Program
 type Compiler struct {
 	logger  logrus.FieldLogger
 	Options Options
+	usage   *usage.Usage
 }
 
 // New returns a new Compiler
 func New(logger logrus.FieldLogger) *Compiler {
-	return &Compiler{logger: logger}
+	return &Compiler{
+		logger: logger,
+		// TODO(@mstoykov): unfortunately otherwise we need to do much bigger rewrite around experimental extensions
+		// and likely more extensions tests. This way tests don't need to care about this and the compiler code
+		// doesn't need to check if it has usage set or not.
+		usage: usage.New(),
+	}
+}
+
+// WithUsage allows the compiler to be given [usage.Usage] to use
+func (c *Compiler) WithUsage(u *usage.Usage) {
+	c.usage = u
 }
 
 // Options are options to the compiler
@@ -64,7 +77,15 @@ func (c *Compiler) Parse(
 	return state.parseImpl(src, filename, commonJSWrap)
 }
 
+const (
+	usageParsedFilesKey   = "usage/parsedFiles"
+	usageParsedTSFilesKey = "usage/parsedTSFiles"
+)
+
 func (ps *parsingState) parseImpl(src, filename string, commonJSWrap bool) (*ast.Program, string, error) {
+	if err := ps.compiler.usage.Uint64(usageParsedFilesKey, 1); err != nil {
+		ps.compiler.logger.WithError(err).Warn("couldn't report usage for " + usageParsedFilesKey)
+	}
 	code := src
 	if commonJSWrap { // the lines in the sourcemap (if available) will be fixed by increaseMappingsByOne
 		code = ps.wrap(code, filename)
@@ -97,6 +118,9 @@ func (ps *parsingState) parseImpl(src, filename string, commonJSWrap bool) (*ast
 	}
 
 	if ps.compatibilityMode == lib.CompatibilityModeExperimentalEnhanced {
+		if err := ps.compiler.usage.Uint64(usageParsedTSFilesKey, 1); err != nil {
+			ps.compiler.logger.WithError(err).Warn("couldn't report usage for " + usageParsedTSFilesKey)
+		}
 		code, ps.srcMap, err = esbuildTransform(src, filename)
 		if err != nil {
 			return nil, "", err