Dockerignore

Dockerignore

wslc build sends the build context as-is, with no .dockerignore support of its own. wip build fills that gap: it reads .dockerignore from the build context, stages only the files that survive it, and hands wslc the filtered copy.

For a large project this is the difference between shipping a few megabytes and shipping node_modules/ plus .git/.

Where the file is read from

The .dockerignore at the root of the build context — that is, next to whatever context: resolves to, not necessarily next to wip.yml:

interaction:
  build:
    type: build
    context: .          # relative to wip.yml's directory
    tag: myapp:dev

Under Compose Native Mode, each service's build.context gets its own .dockerignore treatment when wip up builds it. See Compose Build.

Pattern rules

The same gitignore-style rules the Docker CLI uses:

Pattern	Matches
node_modules	any path component named node_modules, at any depth
/node_modules	only at the context root (leading / anchors)
tmp/	same as tmp — a trailing slash is stripped
*.log	any .log file at any depth
build/**/*.o	globs with / are matched against the full relative path
!keep.log	negation — re-includes something an earlier rule excluded
# …, blank lines	ignored

Details that matter in practice:

• Later rules win. Rules are applied in order; the last one that matches decides.
• A pattern with no / is implicitly **/pattern — it matches at any depth.
• Matching a directory excludes everything under it. Every prefix of a path is tested, so node_modules excludes node_modules/pkg/index.js without needing a /** suffix.
• Dotfiles are matched. * matches .env.

Staging behavior

$ wip build
wip: staging build context (/home/me/my-project)
wip: copying build context files: 1240/1240

• If .dockerignore is missing or has no effective rules, the context is passed through in place — no copy at all.
• Otherwise wip copies the included files into a temporary directory, runs the build from there, and removes it afterward.
• The walk prunes ignored directories instead of descending into them. A 3 GB node_modules/ is never walked, let alone copied — unless a later negated rule (!node_modules/pkg) could match something beneath it, in which case pruning is skipped for correctness.
• Symlinks are copied as symlinks, never dereferenced. Following them could pull arbitrary host files (~/.ssh/id_rsa) into the context.

Progress is reported on its own thread, so one very large file doesn't make the copy look hung.

Interaction with the shadow context

If shadow_context: is configured and applicable, the same .dockerignore filtering feeds the persistent Windows-side shadow directory instead of a throwaway temp dir — so only added/changed files are copied on later builds. See Shadow Build Context.

Why the build runs from inside the context

wslc build crashes with ERROR_UNHANDLED_EXCEPTION when handed an absolute context path, so wip changes into the staged directory and passes . instead. You'll see this reflected in --debug output:

wip: [debug] running: wslc.exe build -t myapp:dev .

A good starting .dockerignore

.git
.dockerignore
node_modules
tmp
log
coverage
*.log
.env

Note this is separate from sync.exclude, which controls the rsync mirror rather than the build context — they often overlap but serve different steps. See Source Sync.

Related

• wip build
• Shadow Build Context
• Compose Build