Store default source in the Function struct

Read the default source envvar as part of initialization in `main` and store it
in the `Function` struct rather than using a global variable. This is tidier and
lets us run our tests in parallel.

Signed-off-by: Adam Wolfe Gordon <[email protected]>

Author: adamwg

fn.go

@@ -26,8 +26,6 @@ import (
 	"github.com/crossplane/function-sdk-go/response"
 )
 
-var defaultSource = os.Getenv("FUNCTION_GO_TEMPLATING_DEFAULT_SOURCE")
-
 // osFS is a dead-simple implementation of [io/fs.FS] that just wraps around
 // [os.Open].
 type osFS struct{}
@@ -40,8 +38,9 @@ func (*osFS) Open(name string) (fs.File, error) {
 type Function struct {
 	fnv1.UnimplementedFunctionRunnerServiceServer
 
-	log  logging.Logger
-	fsys fs.FS
+	log           logging.Logger
+	fsys          fs.FS
+	defaultSource string
 }
 
 const (
@@ -62,10 +61,10 @@ func (f *Function) RunFunction(_ context.Context, req *fnv1.RunFunctionRequest)
 		response.Fatal(rsp, errors.Wrapf(err, "cannot get Function input from %T", req))
 		return rsp, nil
 	}
-	if in.Source == "" && defaultSource != "" {
+	if in.Source == "" && f.defaultSource != "" {
 		in.Source = v1beta1.FileSystemSource
 		in.FileSystem = &v1beta1.TemplateSourceFileSystem{
-			DirPath: defaultSource,
+			DirPath: f.defaultSource,
 		}
 	}
 

fn_test.go

@@ -973,12 +973,10 @@ func TestRunFunction(t *testing.T) {
 
 	for name, tc := range cases {
 		t.Run(name, func(t *testing.T) {
-			// NOTE: This means we can't run tests in parallel.
-			defaultSource = tc.args.defaultSource
-
 			f := &Function{
-				log:  logging.NewNopLogger(),
-				fsys: testdataFS,
+				log:           logging.NewNopLogger(),
+				fsys:          testdataFS,
+				defaultSource: tc.args.defaultSource,
 			}
 			rsp, err := f.RunFunction(tc.args.ctx, tc.args.req)
 

main.go

@@ -2,6 +2,8 @@
 package main
 
 import (
+	"os"
+
 	"github.com/alecthomas/kong"
 
 	"github.com/crossplane/function-sdk-go"
@@ -26,8 +28,9 @@ func (c *CLI) Run() error {
 
 	return function.Serve(
 		&Function{
-			log:  log,
-			fsys: &osFS{},
+			log:           log,
+			fsys:          &osFS{},
+			defaultSource: os.Getenv("FUNCTION_GO_TEMPLATING_DEFAULT_SOURCE"),
 		},
 		function.Listen(c.Network, c.Address),
 		function.MTLSCertificates(c.TLSCertsDir),