From f950dc99426014f3973b2c9193ee5eecf515e39b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olivier=20Mengu=C3=A9?= <dolmen@cpan.org>
Date: Tue, 28 Oct 2025 09:13:35 +0100
Subject: [PATCH] feat(makefile): simplify validate-go-version (#3147)

Since Go 1.21 the go toolchain validates strictly the "go" version
directive in go.mod, and downloads and uses the requested toolchain if
necessary. See https://go.dev/doc/toolchain

So we can just run "go list" to tell the Go toolchain to validate our
build environment according to go.mod.

To extract the "go" directive version from go.mod (used to select the
Docker build image) we also use "go list".
---
 Makefile | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index 20ed88c9..06471100 100644
--- a/Makefile
+++ b/Makefile
@@ -36,13 +36,12 @@ REPOSITORY ?= oauth2-proxy
 DATE := $(shell date +"%Y%m%d")
 .NOTPARALLEL:
 
-GO_MAJOR_VERSION = $(shell $(GO) version | cut -c 14- | cut -d' ' -f1 | cut -d'.' -f1)
-GO_MINOR_VERSION = $(shell $(GO) version | cut -c 14- | cut -d' ' -f1 | cut -d'.' -f2)
+# The go version in go.mod used for the Docker build toolchain, without the patch
+GO_MOD_VERSION_MINOR := $(shell $(GO) list -f '{{printf "%.4s" .Module.GoVersion}}' )
 
-GO_MOD_VERSION = $(shell sed -En 's/^go ([[:digit:]]\.[[:digit:]]+)\.[[:digit:]]+/\1/p' go.mod)
-MINIMUM_SUPPORTED_GO_MAJOR_VERSION = $(shell echo ${GO_MOD_VERSION} | cut -d' ' -f1 | cut -d'.' -f1)
-MINIMUM_SUPPORTED_GO_MINOR_VERSION = $(shell echo ${GO_MOD_VERSION} | cut -d' ' -f1 | cut -d'.' -f2)
-GO_VERSION_VALIDATION_ERR_MSG = Golang version is not supported, please update to at least $(MINIMUM_SUPPORTED_GO_MAJOR_VERSION).$(MINIMUM_SUPPORTED_GO_MINOR_VERSION)
+# From go1.21 go will transparently download the toolchain declared in go.mod. https://go.dev/doc/toolchain
+# We don't need to keep this message updated: the important info is in go.mod.
+GO_VERSION_VALIDATION_ERR_MSG = Golang version is not supported, please update to at least go1.21
 
 ifeq ($(COVER),true)
 TESTCOVER ?= -coverprofile c.out
@@ -56,7 +55,7 @@ build: validate-go-version clean $(BINARY) ## Build and create oauth2-proxy bina
 $(BINARY):
 	CGO_ENABLED=0 $(GO) build -a -installsuffix cgo -ldflags="-X github.com/oauth2-proxy/oauth2-proxy/v7/pkg/version.VERSION=${VERSION}" -o $@ github.com/oauth2-proxy/oauth2-proxy/v7
 
-DOCKER_BUILDX_COMMON_ARGS     ?= --build-arg BUILD_IMAGE=docker.io/library/golang:${GO_MOD_VERSION}-bookworm --build-arg VERSION=${VERSION}
+DOCKER_BUILDX_COMMON_ARGS     ?= --build-arg BUILD_IMAGE=docker.io/library/golang:$(GO_MOD_VERSION_MINOR)-bookworm --build-arg VERSION=$(VERSION)
 
 DOCKER_BUILD_PLATFORM         ?= linux/amd64,linux/arm64,linux/ppc64le,linux/arm/v7,linux/s390x
 DOCKER_BUILD_RUNTIME_IMAGE    ?= gcr.io/distroless/static:nonroot
@@ -158,15 +157,7 @@ lint: validate-go-version ## Lint all files using golangci-lint
 
 .PHONY: validate-go-version
 validate-go-version: ## Validate Go environment requirements
-	@if [ $(GO_MAJOR_VERSION) -gt $(MINIMUM_SUPPORTED_GO_MAJOR_VERSION) ]; then \
-		exit 0 ;\
-	elif [ $(GO_MAJOR_VERSION) -lt $(MINIMUM_SUPPORTED_GO_MAJOR_VERSION) ]; then \
-		echo '$(GO_VERSION_VALIDATION_ERR_MSG)';\
-		exit 1; \
-	elif [ $(GO_MINOR_VERSION) -lt $(MINIMUM_SUPPORTED_GO_MINOR_VERSION) ] ; then \
-		echo '$(GO_VERSION_VALIDATION_ERR_MSG)';\
-		exit 1; \
-	fi
+	@$(GO) list . >/dev/null || { echo '$(GO_VERSION_VALIDATION_ERR_MSG)'; exit 1; }
 
 # local-env can be used to interact with the local development environment
 # eg: