There are many ways to contribute to Rustfmt. This document lays out what they
are and has information for how to get started. If you have any questions about
-contributing or need help with anything, please ping nrc on irc, #rust-tools is
-probably the best channel. Feel free to also ask questions on issues, or file
-new issues specifically to get help.
+contributing or need help with anything, please ping nrc on irc, #rust-dev-tools
+on irc.mozilla.org is probably the best channel. Feel free to also ask questions
+on issues, or file new issues specifically to get help.
+All contributors are expected to follow our [Code of
+Conduct](CODE_OF_CONDUCT.md).
## Test and file issues
identified.
Without explicit settings, the tests will be run using rustfmt's default
-configuration. It is possible to run a test using non-default settings by
-including configuration parameters in comments at the top of the file. For
-example: to use 3 spaces per tab, start your test with
+configuration. It is possible to run a test using non-default settings in several
+ways. Firstly, you can include configuration parameters in comments at the top
+of the file. For example: to use 3 spaces per tab, start your test with
`// rustfmt-tab_spaces: 3`. Just remember that the comment is part of the input,
so include in both the source and target files! It is also possible to
explicitly specify the name of the expected output file in the target directory.
-Use `// rustfmt-target: filename.rs` for this. Finally, you can use a custom
+Use `// rustfmt-target: filename.rs` for this. You can also specify a custom
configuration by using the `rustfmt-config` directive. Rustfmt will then use
that toml file located in `./tests/config/` for its configuration. Including
`// rustfmt-config: small_tabs.toml` will run your test with the configuration
-file found at `./tests/config/small_tabs.toml`.
+file found at `./tests/config/small_tabs.toml`. The final option is used when the
+test source file contains no configuration parameter comments. In this case, the
+test harness looks for a configuration file with the same filename as the test
+file in the `./tests/config/` directory, so a test source file named `test-indent.rs`
+would need a configuration file named `test-indent.toml` in that directory. As an
+example, the `issue-1111.rs` test file is configured by the file
+`./tests/config/issue-1111.toml`.
+## Debugging
+
+Some `rewrite_*` methods use the `debug!` macro for printing useful information. These messages can be printed by using the environment variable `RUST_LOG=rustfmt=DEBUG`. These traces can be helpful in understanding which part of the code was used and get a better grasp on the execution flow.
## Hack!
-Here are some [good starting issues](https://github.com/nrc/rustfmt/issues?q=is%3Aopen+is%3Aissue+label%3Aeasy).
+Here are some [good starting issues](https://github.com/rust-lang-nursery/rustfmt/issues?q=is%3Aopen+is%3Aissue+label%3Agood-first-issue).
If you've found areas which need polish and don't have issues, please submit a
PR, don't feel there needs to be an issue.
There are different nodes for every kind of item and expression in Rust. For
more details see the source code in the compiler -
[ast.rs](https://dxr.mozilla.org/rust/source/src/libsyntax/ast.rs) - and/or the
-[docs](http://manishearth.github.io/rust-internals-docs/syntax/ast/index.html).
+[docs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/ast/index.html).
Many nodes in the AST (but not all, annoyingly) have a `Span`. A `Span` is a
range in the source code, it can easily be converted to a snippet of source
take a context which contains information used for parsing, the current block
indent, and a configuration (see below).
+##### Rewrite and Indent
+
To understand the indents, consider
```
more width, then call the function again with more space.
Since it is common for callers to bail out when a callee fails, we often use a
-`try_opt!` macro to make this pattern more succinct.
+`?` operator to make this pattern more succinct.
One way we might find out that we don't have enough space is when computing how much
space we have. Something like `available_space = budget - overhead`. Since
widths are unsized integers, this would cause underflow. Therefore we use
-checked subtraction: `available_space = try_opt!(budget.checked_sub(overhead))`.
-`checked_sub` returns an `Option`, and if we would underflow `try_opt!` returns
+checked subtraction: `available_space = budget.checked_sub(overhead)?`.
+`checked_sub` returns an `Option`, and if we would underflow `?` returns
`None`, otherwise we proceed with the computed space.
+##### Rewrite of list-like expressions
+
Much syntax in Rust is lists: lists of arguments, lists of fields, lists of
array elements, etc. We have some generic code to handle lists, including how to
space them in horizontal and vertical space, indentation, comments between
and `ListFormatting` the key structure for configuration. You'll need to make a
`ListItems` for input, this is usually done using `itemize_list`.
+##### Configuration
+
Rustfmt strives to be highly configurable. Often the first part of a patch is
creating a configuration option for the feature you are implementing. All
-handling of configuration options is done in [src/config.rs](src/config.rs). Look for the
+handling of configuration options is done in [src/config/mod.rs](src/config/mod.rs). Look for the
`create_config!` macro at the end of the file for all the options. The rest of
the file defines a bunch of enums used for options, and the machinery to produce
the config struct and parse a config file, etc. Checking an option is done by
-accessing the correct field on the config struct, e.g., `config.max_width`. Most
+accessing the correct field on the config struct, e.g., `config.max_width()`. Most
functions have a `Config`, or one can be accessed via a visitor or context of
some kind.
projects / rust.git / blobdiff