From 4c44d5c785fd7beda6a748a845d8355eedd4ce31 Mon Sep 17 00:00:00 2001
From: Niels Henrik Hagen <nhhagen@gmail.com>
Date: Thu, 28 Nov 2024 22:36:51 +0100
Subject: [PATCH] Refactor config resolution

---
 bootstrap2.go   | 28 +++++++++-------------------
 internal/env.go | 13 +++++++++++++
 options.go      | 18 ++++++++++++++----
 3 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/bootstrap2.go b/bootstrap2.go
index 339f2613..98d705c7 100644
--- a/bootstrap2.go
+++ b/bootstrap2.go
@@ -20,7 +20,7 @@ func Start(ctx context.Context, options ...Option) (context.Context, context.Can
 		return ctx, context.CancelFunc(func() {}), nil
 	}
 
-	err := verifyEnvVarsSet(
+	err := internal.VerifyEnvVarsSet(
 		internal.DatadogAPMEndpoint,
 		internal.DatadogDSDEndpoint,
 		internal.DatadogService,
@@ -31,12 +31,9 @@ func Start(ctx context.Context, options ...Option) (context.Context, context.Can
 		return ctx, context.CancelFunc(func() {}), err
 	}
 
-	cfg := defaultConfig()
-
-	options = append([]Option{withConfigFromEnvVars()}, options...)
-
-	for _, option := range options {
-		option(cfg)
+	cfg, err := resolveConfig(options)
+	if err != nil {
+		return ctx, context.CancelFunc(func() {}), err
 	}
 
 	ctx, cancel := context.WithCancel(ctx)
@@ -57,7 +54,11 @@ func Start(ctx context.Context, options ...Option) (context.Context, context.Can
 
 func start(_ context.Context, cfg *config) error {
 	startTracer(cfg)
-	return startProfiler(cfg)
+	err := startProfiler(cfg)
+	if err != nil {
+		return err
+	}
+	return nil
 }
 
 func startTracer(cfg *config) {
@@ -96,17 +97,6 @@ func stop(_ *config) {
 	defer profiler.Stop()
 }
 
-func verifyEnvVarsSet(keys ...string) error {
-	for _, key := range keys {
-		val, ok := os.LookupEnv(key)
-		println(key, val)
-		if !ok || val == "" {
-			return fmt.Errorf("required environmental variable not set: %q", key)
-		}
-	}
-	return nil
-}
-
 func getBoolEnv(key string, fallback bool) bool {
 	valStr, ok := os.LookupEnv(key)
 	if !ok {
diff --git a/internal/env.go b/internal/env.go
index 1964ce6f..5b4d5225 100644
--- a/internal/env.go
+++ b/internal/env.go
@@ -1,6 +1,7 @@
 package internal
 
 import (
+	"fmt"
 	"os"
 	"strconv"
 )
@@ -38,3 +39,15 @@ func IsDatadogDisabled() bool {
 	}
 	return val
 }
+
+// VerifyEnvVarsSet checks if the provided environmental variables are defined
+func VerifyEnvVarsSet(keys ...string) error {
+	for _, key := range keys {
+		val, ok := os.LookupEnv(key)
+		println(key, val)
+		if !ok || val == "" {
+			return fmt.Errorf("required environmental variable not set: %q", key)
+		}
+	}
+	return nil
+}
diff --git a/options.go b/options.go
index df98f4fe..79cf8bdc 100644
--- a/options.go
+++ b/options.go
@@ -15,21 +15,31 @@ type config struct {
 	enableExtraProfiling bool
 }
 
-func defaultConfig() *config {
-	return &config{
+func resolveConfig(options []Option) (*config, error) {
+	cfg := &config{
 		enableTracing:        defaultEnableTracing,
 		enableProfiling:      defaultEnableProfiling,
 		enableExtraProfiling: defaultEnableExtraProfiling,
 	}
+	options = append([]Option{withConfigFromEnvVars()}, options...)
+
+	for _, option := range options {
+		err := option(cfg)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return cfg, nil
 }
 
 // Option is used to configure the behaviour of the Datadog integration.
-type Option func(*config)
+type Option func(*config) error
 
 func withConfigFromEnvVars() Option {
-	return func(cfg *config) {
+	return func(cfg *config) error {
 		cfg.enableTracing = getBoolEnv(internal.DatadogEnableTracing, cfg.enableTracing)
 		cfg.enableProfiling = getBoolEnv(internal.DatadogEnableProfiling, cfg.enableProfiling)
 		cfg.enableExtraProfiling = getBoolEnv(internal.DatadogEnableExtraProfiling, cfg.enableExtraProfiling)
+		return nil
 	}
 }