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/ pubspec.yaml pubspec.lock * README.md CHANGELOG.md LICENSE benchmark/ make_lunch.dart packages/ ** bin/ enchilada packages/ ** doc/ getting_started.md example/ lunch.dart packages/ ** lib/ enchilada.dart tortilla.dart guacamole.css src/ beans.dart queso.dart packages/ ** test/ enchilada_test.dart tortilla_test.dart packages/ ** tool/ generate_docs.dart web/ index.html main.dart style.css
pubspec.lock file is only entered into source control if the package
is an application package.
packages directories exists locally after you’ve run
pub get, but won’t be checked 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, this will be checked into source
control. Otherwise, it won’t be.
enchilada/ packages/ ...
Running pub also generates a
packages directory. You will not check
this into source control, and you won’t need to worry too much about its
contents. Consider it pub magic, but not scary magic.
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 it detects that your package contains a changelog file and shows it 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 packages: they
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
lib. Entrypoints—Dart scripts
main() function—cannot go in
lib. If you place a Dart script
lib, you will discover that any
package: imports it contains don’t
resolve. Instead, your entrypoints should go in the appropriate
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
You can, of course, reference a package from within your app. For example, say your source tree looks like this:
myapp/ example/ one/ sub/ index.html
The resulting build directory has the following structure:
build/ example/ one/ packages/ myapp/ style.css sub/ index.html
In this scenario, index.html references the stylesheet using
the relative path
../packages/myapp/style.css. (Note the leading
You can also use a path relative to the root URL, such as
/packages/myapp/style.css, but you must be careful on how you
deploy your app.
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.
Users can reference another package’s assets using URLs that contain
<package> is the name of the package
containing the asset and
<path> is the relative path to the asset within that
For example, let’s say your package wanted to use enchilada’s
styles. In an HTML file in your package, you can add:
<link href="packages/enchilada/guacamole.css" rel="stylesheet">
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. This is perfectly
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
Dart is a web language, so many pub packages will be doing web stuff. That
goes into your package’s
web directory. You’re free to organize the contents
of that to your heart’s content. Go crazy with subdirectories if that makes you
Also, and this is important, any Dart web entrypoints (in other words, Dart
scripts that are referred to in a
<script> tag) go under
web and not
That ensures that a
packages directory is created nearby so that
imports can be resolved correctly.
(You may be asking whether you should put your web-based example programs
web?” Put those in
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.
pub application itself is one example: it’s a simple shell script that
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
using pub global.
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 unittest 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/ 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
doc. We don’t
currently have any guidelines about format or organization within that. Use
whatever markup format that you prefer.
This directory should not just contain docs generated automatically from your source code using dartdocgen. Since that’s pulled directly from the code already in the package, putting those docs in here would be redundant. Instead, this is for tutorials, guides, and other hand-authored documentation in addition to generated API references.
enchilada/ example/ lunch.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.
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