Preparation for #865, which proposes adding a flag which outputs which
config options are used during formatting.
This PR should not make any difference to functionality. A lot of this
was search-and-replace.
Some areas worthy of review/discussion:
- The method for each config item returns a clone of the underlying
value. We can't simply return an immutable reference, as lots of
places in the code expect to be able to pass the returned value as
`bool` (not `&bool). It would be nice if the `bool` items could
return a copy, but the more complex types a borrowed reference... but
unfortunately, I couldn't get the macro to do this.
- A few places (mostly tests and `src/bin/rustfmt.rs`) were overriding
config items by modifying the fields of the `Config` struct directly.
They now use the existing `override_value()` method, which has been
modified to return a `Result` for use by `src/bin/rustfmt.rs`. This
benefits of this are that the complex `file_lines` and `write_mode`
strings are now parsed in one place (`Config.override_value`) instead
of multiple. The disadvantages are that it moves the compile-time
checks for config names to become run-time checks.
* Add (failing) test for #1397
* Fix for #1397
Specifically, we end up double-adding a trailing comma for single-member
struct patterns that are arranged vertically. One is added by write_list
(since such structs return true for needs_trailing_separator), and
another is added by the if in the old code.
* Add spaces_within_square_brackets config option.
Enabling the config enforces spaces within various array/slice brackets.
* Fixed budget-calculations for [] spacing
This commit adds a `codemap` module, and moves the `CodemapSpanUtils`
added in #857 to it. This is preparation for adding more `Codemap`
specific utilities.
Refs #434
