docker-build

Copy package.json and the lockfile first, run the install command, then copy the full source so dependency layers are reused. Add a .dockerignore excluding node_modules, dist, and .git to keep the build context small and cache stable.

The file is usually outside the build context, excluded by .dockerignore, or referenced before it is copied. Check the build context path in docker-compose.yml and run docker build with --progress=plain to see the exact failing instruction.

Prefer docker compose build when the project defines the service in Compose, since it includes build args, targets, and context paths. Running docker build directly may miss those settings and produce a different image.

Use a multi-stage build: copy go.mod and go.sum, run go mod download, then compile in a builder stage. For runtime, choose distroless, scratch, or Debian slim depending on TLS certificates, shell access, and CGO requirements.

Use a pinned image like python:3.12-slim and install dependencies from a lockfile with uv, Poetry, or pip. Keep build tools in a builder stage and copy only runtime files such as migrations, templates, and static assets into the final image.

Use --no-cache when diagnosing suspected cache corruption or stale dependency layers. For ordinary build failures, first locate the failing stage and dependency layer from the logs before discarding the cache.