What's Changed

• Add --expt-relaxed-constexpr to nvcc. by @eyal0 in #1975
• Add --expt-extended-lambda to nvcc. by @eyal0 in #2055
• Remove stray character by @dpassen in #2056
• Fix a bunch of "reference to free variable" warnings by @Hi-Angel in #2058
• Adapt to new AUCTeX mode names in #2059
• Add actionlint support to yaml-ts-mode by @Gavinok in #2064
• docstrings should not exceed 80 characters in width by @gutron in #2060
• fix(stylelint): remove support for deprecated command line arguments by @justinbarclay in #2066
• Add FlyC:0 and updated the mode menu by @JohnC32 in #2035
• option to control whether to display error at point after checking by @taquangtrung in #1987
• Fix(Haskell): Correctly Handle GHC 9.6 Error Output Format by @ayanamists in #2067
• Add a new checker 'r' for R in #2070
• ci: Exclude macos tests below 28.x by @jcs090218 in #2074
• New checker, perl-perlimports by @mavit in #2071
• Add salt-lint as new flycheck checker by @santifa in #2073
• Update vhdl-ghdl error-patterns by @cyrilarnould in #2077
• Support buffers without backing files in Ruff by @cpitclaudel in #2065
• Use project working-directory for python-ruff (#2068) by @corecode in #2076
• Fix ruff error-patterns and error-filter by @wyuenho in #2079
• Refine flycheck-display-errors lifecycle by @wyuenho in #1972
• ruff: --output-format=text replaced with --output-format=concise by @berquist in #2078
• Add flycheck-chktex-extra-flags by @slotThe in #2075
• Update haskell-hlint checker to HLint-3.0 by @jdnavarro in #1809
• Escape single quote in flycheck-chktex-extra-flags docstring. by @bodea in #2081
• yaml-actionlint: only allow inside GitHub workflows dir by @berquist in #2083
• Fix markdown for XML and YAML docs by @dunmaksim in #2088
• Support new puppet-ts-mode by @smoeding in #2095
• feat: Drop support for Emacs 26.x by @jcs090218 in #2104
• ci(test/run.el): Point to .eask by @jcs090218 in #2103
• Fix detection of cuda warnings. by @eyal0 in #2100
• feat: add options for configuring jsonnet by @DinoChiesa in #2105
• Add -Xcompiler option for cuda-nvcc. by @eyal0 in #2107
• c/c++-cppcheck: add flycheck-cppcheck-args variable by @fwinkl in #2110
• Ruby 3.4 compatibility by @aaronjensen in #2111
• ci: Test Emacs 30.1 by @jcs090218 in #2115
• Update flycheck-add-overlay/right-position-in-narrowed-buffer output by @manphiz in #2114

New Contributors

• @Hi-Angel made their first contribution in #2058
• @Gavinok made their first contribution in #2064
• @gutron made their first contribution in #2060
• @justinbarclay made their first contribution in #2066
• @JohnC32 made their first contribution in #2035
• @taquangtrung made their first contribution in #1987
• @ayanamists made their first contribution in #2067
• @santifa made their first contribution in #2073
• @cyrilarnould made their first contribution in #2077
• @corecode made their first contribution in #2076
• @slotThe made their first contribution in #2075
• @jdnavarro made their first contribution in #1809
• @bodea made their first contribution in #2081
• @dunmaksim made their first contribution in #2088
• @smoeding made their first contribution in #2095
• @DinoChiesa made their first contribution in #2105
• @fwinkl made their first contribution in #2110
• @manphiz made their first contribution in #2114

Full Changelog: 34.1...v35.0

New Features

• New syntax checkers
  • [#2015]: PHP with phpcs-changed
  • [#2017]: HAML with haml-lint
  • [#2030]: Add yaml-actionlint checker for GitHub yaml action
    workflows.
  • [#2052]: Sass with Stylelint
  • [#2013]: Nix with statix
  • [#1935]: Chef (Ruby) with cookstyle
  • [#1915]: Markdown with pymarkdown
• [#1873]: Add error explainer to perl-perlcritic.
• [#1875]: Add error-explainer to css-stylelint.
• [#1876]: Add error-explainer for markdownlint checker.
• [#2019]: Add support for RELAX NG schema in xmllint.

Bugs Fixed

• [#1793]: Fix flycheck-ruby-rubocop on buffers with no backing file.

Changes

• [#2026]:Update the possible locations for yamllint's
  configuration file.
• (Breaking) [#1697]: Remove the coq checker.
• (Breaking) [#1935]: Remove the chef-foodcritic checker.
  (it's now replaced by ruby-chef-cookstyle)
• (Breaking) [#2018]: Remove the golint checker.
• (Breaking) Remove the ruby-rubylint checker.
• [#1704]: The tslint checker is deprecated; it will go away in a
  future release.

Note: The changelog for this release is incomplete.

New features and improvements

• The flycheck-verify-setup UI now includes buttons to re-enable manually
  disabled checkers and to try to re-enable automatically disabled checkers
  (command checkers are automatically disabled when their executable cannot be
  found). [GH-1755]
• Error explainers can now return URLs (to show a webpage) or functions (to
  use custom formatting). For example, the Rust checker now renders
  explanations using markdown-view-mode. [GH-1753]
• Enable checkers in many newer TreeSitter-based major modes (think *-ts-mode).

New syntax checkers

• Python with ruff. [GH-2033]

Breaking changes

• Drop support for Emacs 25.
• The variable flycheck-current-errors now contains errors in the order in
  which they were returned by checkers. In previous versions of Flycheck,
  this list was sorted by error position and severity. [GH-1749]

See the full changelog for more information. The flycheck-32 branch was originally frozen in May 2020.

Highlights

• Many checkers and compiler, such as ocaml, rust, eslint, and
  others, include end-line and end-column information. Flycheck can now
  highlight the exact region that they report. Authors of checker definitions
  can use the new :end-line and :end-column arguments in
  flycheck-error-new, or the new end-line and end-column fields in
  error patterns. [GH-1400]

• Errors that checkers return for other files will now be displayed on the
  first line of the current buffer instead of begin discarded. The error list
  indicates which file each error came from, and navigation moves
  automatically moves between files. This change helps with compiled
  languages, where an error in another file may cause the current file to be
  considered invalid. Variables flycheck-relevant-error-other-file-show
  and flycheck-relevant-error-other-file-minimum-level control this
  behavior. [GH-1427]

• Flycheck can now draw error indicators in margins in addition to fringes.
  Margins can contain arbitrary characters and images, not just monochrome
  bitmaps, allowing for a better experience on high-DPI screens.
  flycheck-indication-mode controls this behavior, and
  flycheck-set-indication-mode can be used to automatically adjust the
  fringes and margins. Additionally, Flycheck's will now use high-resolution
  fringe bitmaps if the fringe is wide enough [GH-1742, GH-1744]

• Error highlighting is now configurable, using the new
  flycheck-highlighting-style variable: instead of applying
  level-dependent faces (typically with wavy underlines), Flycheck can now
  insert delimiters around errors, or mix styles depending on how many lines
  an error covers. Additionally, stipples are added in the fringes to
  indicate errors that span multiple lines. [GH-1743]

New features and improvements

• Flycheck can now trigger a syntax check automatically after switching
  buffers, using the idle-buffer-switch option in
  flycheck-check-syntax-automatically. This is useful when errors in a
  file are due to problems in a separate file. Variables
  flycheck-idle-buffer-switch-delay and
  flycheck-buffer-switch-check-intermediate-buffers control the
  functionality. [GH-1297]
• Flycheck will now use Emacs' native XML parsing when libXML fails. This
  behavior can be changed by customizing flycheck-xml-parser. [GH-1349]
• flycheck-verify-setup now shows more clearly which checkers
  will run in the buffer, and which are misconfigured. [GH-1478]
• Flycheck now locates checker executables using a customizable function,
  flycheck-executable-find. The default value of this function allows
  relative paths (set e.g. in file or dir-local variables) in addition to
  absolute paths and executable names. [GH-1485]
• Checkers that report error positions as a single offset from the start of
  the file can use the new flycheck-error-new-at-pos constructor instead
  of converting that position to a line and a column. [GH-1400]
• Config-file variables can now be set to a list of file names. This is
  useful for checkers like mypy which don't run correctly when called from a
  subdirectory without passing an explicit config file. [GH-1711]
• Thanks to algorithmic improvements in error reporting, Flycheck is now much
  faster in large buffers. [GH-1750]

New syntax checkers:

• Awk with gawk [GH-1708]
• Bazel with bazel-buildifier [GH-1613]
• CUDA with cuda-nvcc [GH-1508]
• CWL with schema-salad-tool [GH-1361]
• Elixir with credo [GH-1062]
• JSON with json-jq [GH-1568]
• Jsonnet with jsonnet [GH-1345]
• MarkdownLint CLI with markdownlint [GH-1366]
• mypy with python-mypy [GH-1354]
• Nix with nix-linter [GH-1530]
• Opam with opam lint [GH-1532]
• protobuf-prototool with prototool [GH-1591]
• Rust with rust-clippy [GH-1385]
• Ruumba with eruby-ruumba [GH-1616]
• Staticcheck with go-staticheck [GH-1541]
• terraform with terraform fmt, tflint [GH-1586]
• Tcl with nagelfar [GH-1365]
• Text prose with textlint [GH-1534]
• VHDL with ghdl [GH-1160]

Checker improvements:

• python-pylint and python-flake8 are now invoked with python -c,
  to make it easier to change between Python 2 and Python 3. [GH-1113]
• Add flycheck-perl-module-list to use specified modules when
  syntax checking code with the perl checker. [GH-1207]
• rust-cargo now uses cargo check and cargo test. [GH-1289]
• Add flycheck-ghc-stack-project-file for the
  haskell-stack-ghc checker. [GH-1316]
• Add flycheck-cppcheck-suppressions-file to pass a suppressions
  file to cppcheck. [GH-1329]
• Add --force-exclusion flag to rubocop command. [GH-1348]
• Flycheck now uses ESLint's JSON output instead of checkstyle XML. [GH-1350]
• Add flychjeck-eslint-args to pass arguments to javascript-eslint.
  [GH-1360]
• Flycheck will now execute rubocop from the directory where a Gemfile
  is located. If a Gemfile does not exist, the old behaviour of running
  the command from the directory where .rubocop.yml is found will be
  used. [GH-1368]
• Add flycheck-sh-bash-args to pass arguments to sh-bash. [GH-1439]
• haskell-stack-ghc will not try to install GHC anymore. [GH-1443]
• Add flycheck-ghdl-ieee-library to select which standard IEEE
  library to use for ghdl. [GH-1547]
• The javascript-eslint checker now supports typescript-mode by
  default.
• Add flycheck-erlang-rebar3-profile to select which profile to
  use when compiling erlang with rebar3. [GH-1560]
• Add flycheck-relevant-error-other-file-show to avoid showing errors
  from other files. [GH-1579]
• The nix-linter checker now has an error explainer. [GH-1586]
• The Emacs Lisp checker can now run in buffers not backed by files. [GH-1695]

Breaking changes

• Remove the javascript-jscs checker. [GH-1024]
• Remove the elixir-dogma checker. [GH-1450]
• rust-cargo now requires Rust 1.17 or newer. [GH-1289]
• rust now requires 1.18 or newer. [GH-1501]
• Rename flycheck-cargo-rustc-args to flycheck-cargo-check-args.
  [GH-1289]
• rust-cargo does not use the variable flycheck-rust-args anymore.
  [GH-1289]
• Improve detection of default directory for haskell-ghc to consider
  hpack project files. [GH-1435]
• Replace go tool vet with go vet. [GH-1548]
• Remove the deprecated go-megacheck checker, which is replaced by
  go-staticcheck. [GH-1583]

Many thanks to all the people who contributed for this release 🎉

See the full changelog for more information.

Breaking changes

The rust-cargo checker now requires Rust 1.15 or newer. On the other hand, the checker is now capable to test integration tests, examples and benchmarks.

We have removed the javascript-gjslint checker following the deprecation of the Closure Linter.

Notable changes

We have added 10 new checkers: protobuf-protoc, systemd-analyze, nix-instantiate, dockerfile-hadolint, asciidoctor, less-stylelint, ruby-reek, go-megacheck, llvm-llc, and proselint.

Many thanks to all the people who contributed for this release 🎉

Notable changes:

• Flycheck now checks Elixir with dogma and Sass/SCSS with sass-lint. Jade support is gone in favour of Pug support, following the renaming of the language.
• Flycheck can now show explanations for the error under point with C-c ! e—currently support for Rust is included, more to come. The command previously bound to C-c ! e is not bound anymore, use M-x flycheck-set-checker-executable.
• Flycheck now automatically disables syntax checker which are not available in exec-path, and does not longer attempt to find executables before each syntax check. As such you explicitly need to re-enable a syntax checker with C-u C-c ! x if you install the tool after visiting a file.
• Using the same infrastructure Flycheck now automatically disables eslint if there is no eslint configuration for the current buffer. This introduces a slight delay when visiting Javascript buffers, but prevents errors from invoking eslint with no configuration. As part of this change support for explicit eslint configuration was removed—eslint's own configuration search is far superior.
• Likewise the explicit configuration for luacheck was removed as well, in favour of luacheck's own configuration file search, for the same reasons.
• Syntax checker definitions require :modes now; syntax checkers without :modes signal an error.

Further information

• Detailed list of changes

This release adds a new :working-directory property to syntax checkers which lets syntax checkers control the directory they are invoked from. The Haskell syntax checkers use this feature to run from the project directory if possible.

Javascript

This release replaces the option flycheck-eslint-rulesdir with flycheck-eslint-rules-directories which is now a list of rules directories for eslint.

Rust

The Rust syntax checkers now require Rust 1.7 or newer, and support the error format of Rust 1.12 and newer.

Miscellaneous

For more information please read the changelog.

This release adds new options for cppcheck and Rust, adds support for Geiser Mode and fixes two bugs.

Take a look at the changelog for more information.

This release brings new syntax checkers for Go, Markdown and TypeScript, and makes the Emacs Lisp Checkdoc syntax checker use any Checkdoc options from your Emacs session.

The PHP Code Sniffer syntax checker now requires PHP Code Sniffer 2.6 or newer, which is the latest release at the time of writing.

See the Changelog for more information.

After a longer hiatus it's time for another release which not only brings new languages, features and bug fixes but also is a major step forward for Flycheck as a community project. We now have a Code of Conduct, a new and much improved Contributor's Guide and a Gitter channel for you to ask question and discuss further development of Flycheck.

From now on we'll release more frequently. The version number will just monotonically increase; we'll still not make any guarantees about backwards compatibility.

In another major development we're going back to a Sphinx-based website and manual, because Texinfo is too much effort to maintain and write, and to arcane a format to force it upon our contributors. Unfortunately this means that we'll no longer include an Info manual in Flycheck's packages, so you can't read Flycheck's manual in Emacs' Info viewer anymore.

Please take a look at the Changelog for information about new features and bug fixes.