Pub Package Layout Conventions
Part of a healthy code ecosystem is consistent conventions. When we all do the same thing the same way, it makes it easier for us to learn our way around each other’s work. It also makes it easier to write tools that can automatically do things for us.
When you build a pub package,
we have a set of conventions we encourage you to follow.
They describe how you organize the files and directories within your
package, and how to name things. You don’t have to have every single thing
these guidelines specify. If your package doesn’t have binaries, it doesn’t
need a directory for them. But if it does, you’ll make everyone’s life easier
if you call it
To give you a picture of the whole enchilada, here’s what a complete package
enchilada) that uses every corner of these guidelines
would look like:
enchilada/ .packages * pubspec.yaml pubspec.lock ** README.md CHANGELOG.md LICENSE benchmark/ make_lunch.dart bin/ enchilada doc/ api/ *** getting_started.md example/ main.dart lib/ enchilada.dart tortilla.dart guacamole.css src/ beans.dart queso.dart test/ enchilada_test.dart tortilla_test.dart tool/ generate_docs.dart web/ index.html main.dart style.css
.packages file exists after you’ve run
Don’t check it into source control.
pubspec.lock file exists after you’ve run
Leave it out of source control unless your package is an
doc/api directory exists locally after you’ve run
Don’t check the
api directory into source control.
enchilada/ pubspec.yaml pubspec.lock
Every package has a pubspec, a file named
pubspec.yaml, in the root directory of the package. That’s what makes it a
Once you’ve run
pub upgrade, or
pub downgrade on the package, you will also have a
pubspec.lock. If your package is an application
package, check the lockfile into source
control. Otherwise, don’t.
Running pub also generates a
Don’t check this into source control.
The open source community has a few other files that commonly appear at
the top level of a project:
AUTHORS, etc. If you use any
of those, they can go in the top level of the package too.
For more information, see Pubspec Format.
One file that’s very common in open source is a README file that describes the project. This is especially important in pub. When you upload to pub.dartlang.org, your README is shown on the page for your package. This is the perfect place to introduce people to your code.
If your README ends in
.mdown, it is parsed as
To show users the latest changes to your package, you can include a changelog file where you can write a short note about the changes in your latest release. When you upload your package to pub.dartlang.org, your package’s changelog file (if any) appears in the changelog tab.
If your CHANGELOG ends in
.mdown, it is parsed as
The following directory structure shows the
lib portion of enchilada:
enchilada/ lib/ enchilada.dart tortilla.dart
Many packages are library
define Dart libraries that other packages can import and use.
These public Dart library files go inside a directory called
Most packages define a single library that users can import. In that case,
its name should usually be the same as the name of the package, like
enchilada.dart in the example here. But you can also define other
libraries with whatever names make sense for your package.
When you do, users can import these libraries using the name of the package and the library file, like so:
import 'package:enchilada/enchilada.dart'; import 'package:enchilada/tortilla.dart';
If you want to organize your public libraries, you can also create
lib. If you do that, users will specify that path
when they import it. Say you have the following file hierarchy:
enchilada/ lib/ some/ path/ olives.dart
olives.dart as follows:
Note that only libraries should be in
Entrypoints—Dart scripts with a
lib. If you place a Dart script inside
you will discover that any
package: imports it contains don’t
resolve. Instead, your entrypoints should go in the appropriate
For more information on library packages, see Create Library Packages.
Dart scripts placed inside of the
bin directory are public. Any package
that depends on your package can run scripts from your package’s
pub run. Any package
can run scripts from your package’s bin directory using
If you intend for your package to be depended on,
and you want your scripts to be private to your package, place them
in the top-level
If you do not intend for your package to be depended on, you can leave your
enchilada/ lib/ guacamole.css
While most library packages exist to let you reuse Dart code, you can also reuse other kinds of content. For example, a package for Bootstrap might include a number of CSS files for consumers of the package to use.
These go in the top-level
lib directory. You can put any kind of file
in there and organize it with subdirectories however you like.
You can reference another package’s assets using the resource package.
For more information about using assets, see Pub Assets and Transformers.
enchilada/ lib/ src/ beans.dart queso.dart
The libraries inside
lib are publicly visible: other packages are free to
import them. But much of a package’s code is internal implementation libraries
that should only be imported and used by the package itself. Those go inside a
src. You can create subdirectories in there if
it helps you organize things.
You are free to import libraries that live in
lib/src from within other Dart
code in the same package (like other libraries in
lib, scripts in
tests) but you should never import from another package’s
Those files are not part of the package’s public API, and they might change in
ways that could break your code.
When you use libraries from within your own package, even code in
can (and should) still use
package: to import them. For example:
The name you use here (in this case
enchilada) is the name you specify for
your package in its pubspec.
enchilada/ web/ index.html main.dart style.css
For web packages, place entrypoint code—Dart scripts that include
main() and supporting files, such as CSS or HTML—under
You can organize the
web directory into subdirectories if you like.
Put library code under
If the library isn’t imported directly by code under
web, or by
another package, put it under
Put web-based examples under
Public assets for tips on where to put assets,
such as images.
enchilada/ bin/ enchilada
Some packages define programs that can be run directly from the command
line. These can be shell scripts or any other scripting language,
including Dart. The
pub application itself is one example: it’s
a simple shell script that invokes
If your package defines code like this, put it in a directory named
You can run that script from anywhere on the command line, if you set it up
Tests and benchmarks
enchilada/ test/ enchilada_test.dart tortilla_test.dart
Every package should have tests. With pub, the convention is
that these go in a
test directory (or some directory inside it if you like)
_test at the end of their file names.
Typically, these use the test package.
enchilada/ benchmark/ make_lunch.dart
Packages that have performance critical code may also include benchmarks. These test the API not for correctness but for speed (or memory use, or maybe other empirical metrics).
enchilada/ doc/ api/ getting_started.md
If you’ve got code and tests, the next piece you might want
is good documentation. That goes inside a directory named
When you run the dartdoc
tool, it places the API documentation, by default, under
Since the API documentation is generated from the source code,
you should not place it under source control.
Other than the generated
api, we don’t
have any guidelines about format or organization of the documentation
that you author. Use whatever markup format that you prefer.
enchilada/ example/ main.dart
Code, tests, docs, what else
could your users want? Standalone example programs that use your package, of
course! Those go inside the
example directory. If the examples are complex
and use multiple files, consider making a directory for each example. Otherwise,
you can place each one right inside
This is an important place to consider using
package: to import files from
your own package. That ensures the example code in your package looks exactly
like code outside of your package would look.
Internal tools and scripts
enchilada/ tool/ generate_docs.dart
Mature packages often have little helper scripts and programs that people run while developing the package itself. Think things like test runners, documentation generators, or other bits of automation.
Unlike the scripts in
bin, these are not for external users of the package.
If you have any of these, place them in a directory called