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android/platform/external/ktfmt/58233e5
commit
58233e59660ff8bf7f6e16aed33512e1fa67fb50
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author
Carmi Grushko <carmi@fb.com>
Wed Feb 12 16:09:08 2020 -0800
committer
Facebook Github Bot <facebook-github-bot@users.noreply.github.com>
Wed Feb 12 16:10:53 2020 -0800
tree
32577067d12badeccbca93dff644ac8fb3c3cae3
parent
853ac5dcb8bbcdd9884aaac90edd8d10a45c50e7 [diff]
Format stdin -> stdout when "-" is passed as a file name argument

Reviewed By: strulovich

Differential Revision: D19864750

fbshipit-source-id: cea1d6c7bee9fb4839bb0b77a1d045f69f75da94
2 files changed
tree: 32577067d12badeccbca93dff644ac8fb3c3cae3
  1. .github/
  2. core/
  3. docs/
  4. vendor/
  5. .gitignore
  6. .gitmodules
  7. CODE_OF_CONDUCT.md
  8. CONTRIBUTING.md
  9. LICENSE
  10. pom.xml
  11. README.md
README.md

ktfmt

ktfmt is a program that pretty-prints (formats) Kotlin code, based on google-java-format.

Note that ktfmt still has some rough edges which we're constantly working on fixing.

Demo

Before FormattingFormatted by ktfmt
Originalktfmt

For comparison, the same code formatted by ktlint and IntelliJ:

Formatted by ktlintFormatted by IntelliJ
ktlintIntelliJ

Using from the command-line

  • Make sure the vendor/google-java/format submodule is populated. Either clone with submodules (git pull --recurse-submodules https://github.com/facebookincubator/ktfmt.git) or populate the submodule after cloning (git submodule update --init)
  • Run mvn install
  • Run java -jar core/target/ktfmt-0.1-SNAPSHOT-jar-with-dependencies.jar

FAQ

ktfmt vs ktlint vs IntelliJ

ktfmt uses google-java-format's underlying engine, and as such, many items on google-java-format's FAQ apply to ktfmt as well.

In particular,

  1. ktfmt ignores most existing formatting. It respects existing newlines in some places, but in general, its output is determinstic and is independent of the input code.
  2. ktfmt exposes no configuration options that govern formatting behavior. See https://github.com/google/google-java-format/wiki/FAQ#i-just-need-to-configure-it-a-bit-differently-how for the rationale.

These two properties make ktfmt a good fit in large Kotlin code bases, where consistency is very important.

We created ktfmt because ktlint and IntelliJ sometime fail to produce nice-looking code that fits in 100 columns, as can be seen in the Demo section.

ktfmt uses a 2-space indent; why not 4?

Two reasons -

  1. Many of our projects use a mixture of Kotlin and Java, and we found the back-and-forth in styles to be distracting.
  2. From a pragmatic standpoint, the formatting engine behind google-java-format uses more whitespace and newlines than other formatters. Using an indentation of 4 spaces quickly reaches the maximal column width.

Developer's Guide

Setup

  • Make sure the vendor/google-java/format submodule is populated. Either clone with submodules (git pull --recurse-submodules https://github.com/facebookincubator/ktfmt.git) or populate the submodule after cloning (git submodule update --init)
  • Open pom.xml in IntelliJ. Choose “Open as a Project”
  • The IntelliJ project will unfortunately be broken on import. To fix,
    • Turn off ErrorProne by removing the compiler parameters in IntelliJ at the bottom of “Settings -> Build, Execution, Deployment -> Compiler -> Java Compiler” (see https://github.com/google/google-java-format/issues/417)
    • Right click on “vendor/google-java-format/pom.xml” and choose “Add maven project”

Development

  • Currently, we mainly develop by adding tests to FormatterKtTest.kt.

License

Apache License 2.0