Package layout conventions
When you build a pub package, we encourage you to follow the conventions that this page describes. They describe how you organize the files and directories within your package, and how to name things.
Here’s what a complete package (named
that uses every corner of these guidelines
might look like:
enchilada/ .dart_tool/ * pubspec.yaml pubspec.lock ** LICENSE README.md CHANGELOG.md 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
.dart_tool/ directory exists after you’ve run
dart pub get.
Don’t check it into source control.
To learn more, see
Project specific caching for tools.
pubspec.lock file exists after you’ve run
dart pub get.
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
dart pub get,
dart pub upgrade, or
dart pub downgrade on the package
creates a lockfile, named
If your package is an
check the lockfile into source control. Otherwise, don’t.
For more information, see the pubspec page.
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 the pub.dev site, your
is shown—rendered as Markdown—on the page for your package.
This is the perfect place to introduce people to your code.
For guidance on how to write a great README, see Writing package pages.
CHANGELOG.md file that has a section for
each release of your package,
with notes to help users of your package upgrade.
Users of your package often review the changelog
to discover bug fixes and new features,
or to determine how much effort it will take to upgrade
to the latest version of your package.
To support tools that parse
use the following format:
- Each version has its own section with a heading.
- The version headings are either all level 1 or all level 2.
- The version heading text contains a package version number, optionally prefixed with “v”.
Here’s an example of a
As the example shows, you can add subsections.
# 1.0.1 * Fixed missing exclamation mark in `sayHi()` method. # 1.0.0 * **Breaking change:** Removed deprecated `sayHello()` method. * Initial stable release. ## Upgrading from 0.1.x Change all calls to `sayHello()` to instead be to `sayHi()`. # 0.1.1 * Deprecated the `sayHello()` method; use `sayHi()` instead. # 0.1.0 * Initial development release.
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 Creating packages.
Dart scripts placed inside of the
bin directory are public. If you’re
inside the directory of a package, you can use
dart run to run scripts from the
directories of any other package the package depends on. From any
directory, you can run scripts
from packages that you have activated using
dart pub global activate.
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 don’t 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.
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.
How you import libraries from within your own package depends on the locations of the libraries:
- When reaching inside or outside
lib/(lint: avoid_relative_lib_imports), use
- Otherwise, prefer relative imports.
// When importing from lib/beans.dart import 'src/beans.dart'; // When importing from test/beans_test.dart import 'package:enchilada/src/beans.dart';
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.
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
dart pub global.
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
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
In your examples, use
package: to import files from your own package.
That ensures that the example code in your package looks exactly
like code outside of your package would look.
If you might publish your package, consider creating an example file with one of the following names (case insensitive):
When you publish a package that contains one or more of the above files,
the pub.dev site creates an Example tab to display the first file it finds
(searching in the order shown in the list above).
For example, if your package has many files under its
including a file named
then your package’s Example tab displays the contents of
(parsed as Markdown.)
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
Project-specific caching for tools
.dart_tool/ directory is created when you run
dart pub get
and might be deleted at any time. Various tools use this directory
for caching files specific to your project and/or local machine.
.dart_tool/ directory should never be checked into
source control, or copied between machines.
It is also generally safe to delete the
though some tools might need recompute the cached information.
Example: The dart pub get tool
will dowload and extract dependencies to a global
and then write a
.dart_tool/package_config.json file mapping package names
to directories in the global
.dart_tool/package_config.json file is used by other tools,
such as analyzer, compiler, etc, when they need to resolve statments
When developing a tool that needs project-specific caching,
you might consider using the
because most users already ignore it with
When caching files for your tool in a user’s
you should use a unique subdirectory. To avoid collisions,
subdirectories of the form
are reserved for the package named
If your tool isn’t distributed through the pub.dev site,
you might consider publishing a placeholder package in order to
reserve the unique name.
package:build provides a
framework for writing code generation steps.
When running these build steps, files are cached in
This helps speed-up future re-runs of the build steps.