From e2050f8ec87f0cc21a2633feece43a04fa0b5c53 Mon Sep 17 00:00:00 2001
From: Kpa-clawbot <kpaclawbot@outlook.com>
Date: Tue, 5 May 2026 01:12:40 -0700
Subject: [PATCH] fix(docker): default BUILDPLATFORM so plain docker build
 works (fixes #884) (#1069)
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## Summary

Plain `docker build .` (no buildx) fails immediately:

```
Step 1/45 : FROM --platform=$BUILDPLATFORM golang:1.22-alpine AS builder
failed to parse platform : "" is an invalid component of "": platform specifier
component must match "^[A-Za-z0-9_-]+$"
```

`$BUILDPLATFORM` is only auto-populated by buildx; under plain
BuildKit/`docker build` it's empty.

## Fix

Add `ARG BUILDPLATFORM=linux/amd64` before the `FROM` so the variable
always resolves.

## Multi-arch preserved

`docker buildx build --platform=linux/arm64,linux/amd64 .` still
overrides `BUILDPLATFORM` at invocation time — the ARG default only
applies when the caller doesn't set one. The existing CI multi-arch
workflow is unaffected.

Fixes #884

Co-authored-by: meshcore-bot <bot@meshcore.local>
---
 Dockerfile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Dockerfile b/Dockerfile
index 0a8694fc..6b5ca155 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,8 @@
 # Build stage always runs natively on the builder's arch ($BUILDPLATFORM)
 # and cross-compiles to $TARGETOS/$TARGETARCH via Go toolchain. No QEMU.
+# BUILDPLATFORM is auto-set by buildx; default to linux/amd64 so plain
+# `docker build` (without buildx) doesn't fail on an empty platform string.
+ARG BUILDPLATFORM=linux/amd64
 FROM --platform=$BUILDPLATFORM golang:1.22-alpine AS builder
 
 ARG APP_VERSION=unknown