From 16cd1a7561155a264b1a1a2a5850b11c47dc18d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Fri, 15 Sep 2023 15:52:53 +0300
Subject: [PATCH] cmd/geth, internal/flags: print envvar config source and bad
 names (#28119)

---
 cmd/geth/main.go          |  6 +++++-
 internal/flags/helpers.go | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index a1d148d805..f6fa47ad2e 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -249,7 +249,11 @@ func init() {
 	app.Before = func(ctx *cli.Context) error {
 		maxprocs.Set() // Automatically set GOMAXPROCS to match Linux container CPU quota.
 		flags.MigrateGlobalFlags(ctx)
-		return debug.Setup(ctx)
+		if err := debug.Setup(ctx); err != nil {
+			return err
+		}
+		flags.CheckEnvVars(ctx, app.Flags, "GETH")
+		return nil
 	}
 	app.After = func(ctx *cli.Context) error {
 		debug.Exit()
diff --git a/internal/flags/helpers.go b/internal/flags/helpers.go
index bdeb7e38e0..b97f96d59e 100644
--- a/internal/flags/helpers.go
+++ b/internal/flags/helpers.go
@@ -20,9 +20,11 @@ import (
 	"fmt"
 	"os"
 	"regexp"
+	"sort"
 	"strings"
 
 	"github.com/ethereum/go-ethereum/internal/version"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/mattn/go-isatty"
 	"github.com/urfave/cli/v2"
@@ -263,3 +265,37 @@ func AutoEnvVars(flags []cli.Flag, prefix string) {
 		}
 	}
 }
+
+// CheckEnvVars iterates over all the environment variables and checks if any of
+// them look like a CLI flag but is not consumed. This can be used to detect old
+// or mistyped names.
+func CheckEnvVars(ctx *cli.Context, flags []cli.Flag, prefix string) {
+	known := make(map[string]string)
+	for _, flag := range flags {
+		docflag, ok := flag.(cli.DocGenerationFlag)
+		if !ok {
+			continue
+		}
+		for _, envvar := range docflag.GetEnvVars() {
+			known[envvar] = flag.Names()[0]
+		}
+	}
+	keyvals := os.Environ()
+	sort.Strings(keyvals)
+
+	for _, keyval := range keyvals {
+		key := strings.Split(keyval, "=")[0]
+		if !strings.HasPrefix(key, prefix) {
+			continue
+		}
+		if flag, ok := known[key]; ok {
+			if ctx.Count(flag) > 0 {
+				log.Info("Config environment variable found", "envvar", key, "shadowedby", "--"+flag)
+			} else {
+				log.Info("Config environment variable found", "envvar", key)
+			}
+		} else {
+			log.Warn("Unknown config environment variable", "envvar", key)
+		}
+	}
+}