commit | 7d5dcfca4f53f8409be59410c1b696c3dd887ecd | [log] [tgz] |
---|---|---|
author | Bob Nystrom <rnystrom@google.com> | Mon Feb 05 15:30:28 2024 -0800 |
committer | GitHub <noreply@github.com> | Mon Feb 05 15:30:28 2024 -0800 |
tree | d3838bc810c37cf1fcd53374298611a811268790 | |
parent | cd0f2ab42761c0b22486e3441c32c6d570e7c524 [diff] |
Fix bug in subtree merging cost calculation. (#1377) An important optimization during solving is hoisting out a separable Piece subtree, formatting in its own isolated Solver, and then merging the resulting Solution back into the parent Solution. When we merge, we add in all of the data from the subtree to the main one. It's important that doing so yields the exact same result that we would get if we had solved that subtree directly inline in the parent Solution. Unfortunately, the previous code didn't do that. In some cases, pieces that are bound by the subtree Solution would already be bound in the parent one too. In that case, merging would double-count the cost of those pieces. This fixes that by only counting the cost of pieces that weren't already bound in the parent. I ran into this bug while running the large benchmark and it was surprisingly hard to hoist out a small separable test case. The issue wasn't really specific to any particular Piece or syntax. It's really a regression test. The regression tests aren't migrated for the new formatter yet, so I made a new directory "regression_tall" and put it there. I'm not sure if that's ultimately the naming convention we'll want. Also, while I was investigating this, I noticed that ListPiece could theoretically try to format a child Piece separately when doing so wasn't valid because there might be code from a sibling or parent piece on its line. (In practice, that can't happen because the only SequencePiece that doesn't have surrounding brackets is the one top-level sequence for the compilation unit. So there definitely won't be anything before or after that. But if we ever use SequencePiece in other places without brackets, this avoids that becoming a bug.)
The dart_style package defines an automatic, opinionated formatter for Dart code. It replaces the whitespace in your program with what it deems to be the best formatting for it. Resulting code should follow the Dart style guide but, moreso, should look nice to most human readers, most of the time.
The formatter handles indentation, inline whitespace, and (by far the most difficult) intelligent line wrapping. It has no problems with nested collections, function expressions, long argument lists, or otherwise tricky code.
The formatter turns code like this:
// BEFORE formatting if (tag=='style'||tag=='script'&&(type==null||type == TYPE_JS ||type==TYPE_DART)|| tag=='link'&&(rel=='stylesheet'||rel=='import')) {}
into:
// AFTER formatting if (tag == 'style' || tag == 'script' && (type == null || type == TYPE_JS || type == TYPE_DART) || tag == 'link' && (rel == 'stylesheet' || rel == 'import')) {}
The formatter will never break your code—you can safely invoke it automatically from build and presubmit scripts.
The formatter can also apply non-whitespace changes to make your code consistently idiomatic. You must opt into these by passing either --fix
which applies all style fixes, or any of the --fix-
-prefixed flags to apply specific fixes.
For example, running with --fix-named-default-separator
changes this:
greet(String name, {String title: "Captain"}) { print("Greetings, $title $name!"); }
into:
greet(String name, {String title = "Captain"}) { print("Greetings, $title $name!"); }
The formatter is part of the unified dart
developer tool included in the Dart SDK, so most users get it directly from there. That has the latest version of the formatter that was available when the SDK was released.
IDEs and editors that support Dart usually provide easy ways to run the formatter. For example, in WebStorm you can right-click a .dart file and then choose Reformat with Dart Style.
Here's a simple example of using the formatter on the command line:
$ dart format test.dart
This command formats the test.dart
file and writes the result to the file.
dart format
takes a list of paths, which can point to directories or files. If the path is a directory, it processes every .dart
file in that directory or any of its subdirectories.
By default, it formats each file and write the formatting changes to the files. If you pass --output show
, it prints the formatted code to stdout.
You may pass a -l
option to control the width of the page that it wraps lines to fit within, but you're strongly encouraged to keep the default line length of 80 columns.
If you want to use the formatter in something like a presubmit script or commit hook, you can pass flags to omit writing formatting changes to disk and to update the exit code to indicate success/failure:
$ dart format --output=none --set-exit-if-changed .
If you need to run a different version of the formatter, you can globally activate the package from the dart_style package on pub.dev:
$ pub global activate dart_style $ pub global run dart_style:format ...
The package also exposes a single dart_style library containing a programmatic API for formatting code. Simple usage looks like this:
import 'package:dart_style/dart_style.dart'; main() { final formatter = DartFormatter(); try { print(formatter.format(""" library an_entire_compilation_unit; class SomeClass {} """)); print(formatter.formatStatement("aSingle(statement);")); } on FormatterException catch (ex) { print(ex); } }
Before sending an email, see if you are asking a frequently asked question.
Before filing a bug, or if you want to understand how work on the formatter is managed, see how we track issues.