f90-ts-mode is a major mode for editing Fortran 90/2003 (and newer) source
files, based on Emacs's built-in tree-sitter support (requires Emacs 29+)

Changelog (recent):
[10-2026]
  - Transient menu restructured and decomposed.
  - Support for hideshow and outline added.

[09-2026]
  - `f90-ts-mode.el' decomposed into several smaller packages.  Experimental
    `f90-ts-nav' (tree in fortran menu and tree view in side panel) has been
    made optional and requires a separate use-package to load it,
    see `README.md'.
  - `f90-ts-indent-delete-trailing-whitespace' added to automatically delete
    trailing whitespace after indentation operation.
  - Font locking of interface name in deferred procedure declaration fixed.
  - Trimming of trailing whitespace characters in thing-end-of-X navigation
    added.
  - Support for Emacs 29 + tree-sitter 0.20.x added (tested with 29.1, 29.3
    and tree-sitter 0.20.8).
  - Fontification of error nodes fixed if line limitting is enabled.
  - Some issues in comment-region operations fixed (preserve indentation,
    preserve trailing whitespace where possible, keep existing alignment
    with keep options, do not operate outside of region boundaries, add
    missing function `f90-ts-indent-region').
  - Indentation after uncommenting lines in comment-region operation on
    commented lines of code containing leading ampersand or statement label
    fixed.
  - Missing option `keep-or-continued-line' added to
    `f90-ts--indent-options-alist' for indentation selection options.
  - Syntax highlighting, indentation and break/join/fill for string literals
    improved.  This requires a proposed (but not yet merged) tree-sitter
    language grammar extension.  See README.md for more details.
  - Testing with Emacs 31.1 and tree-sitter 0.26 added.

[08-2026]
  - `f90-ts-shift-line-break' as combined break/join function added.
  - Defcustom `f90-ts-font-lock-error` replaced by
    `f90-ts-font-lock-error-show'.  Errors are now always fontified by
    `f90-ts-font-lock-error-face'.  The new defcustom
    `f90-ts-font-lock-error-show' can be used to turn ERROR node
    highlighting on and off, or the number of lines to be highlighted for
    each ERROR node.
  - Jump-to-rightmost-position (within fill-column) to the interactive fill
    operation added.
  - Mark region operations fixed: always consider trimmed region of nodes.
    Some nodes like a whole "subroutine..end subroutine" block contains a
    trailing newline, which should not be considered.  Not consequently
    trimming all spans broke some mark region operations.
  - About, README and MANUAL entries in the fortran and transient popup menu
    to view information about the mode added.
  - Additional font-locking for error regions added.  This can be customized
    by `f90-ts-font-lock-error' and `f90-ts-font-lock-error-face'.
  - Smart end completion of coarray "change team ... end team" blocks fixed.
    It was wrongly assumed that the end statement is "end change team".

Features:
  - Almost all statements up to F2023
  - Syntax highlighting, including syntactically incorrect code
  - Indentation of lines, regions, multiline statements and structure blocks
  - Alignment for multiline statements with rotation and other options
  - Smart end completion
  - Configurable leading ampersand and statement label positions
  - Breaking and joining of continued lines
  - Fill and rebalance operations for lines or regions (with rightmost
    breakpoint selection or interactive break and join session)
  - Region selection based on tree-sitter nodes
  - (Un)commenting regions with configurable prefixes and indentation rules
  - Special comments like doc strings and separators
    (syntax highlighting and indentation options)
  - Keyword highlighting in comments (like TODO, Remark etc.)
  - OpenMP and preprocessor directives
  - Coarray keywords and statements
  - Imenu and a Fortran menu in the menu bar
  - Navigation (defun, things, Xref, side panel tree)
  - Hideshow and outline support (support for external treesit-fold is pending)

Features can be found by the fortran menu or a transient popup bound
to the key C-c C-f.

Installation requires the tree-sitter Fortran grammar, which can be found at
  https://github.com/stadelmanma/tree-sitter-fortran

Basic setup with use-package:

  (use-package f90-ts-mode
    :mode ("\\.f90\\'" . f90-ts-mode))

See the README and MANUAL at https://github.com/mscfd/emacs-f90-ts-mode
for full documentation on options, keybindings, etc.

Bugs and features:
  https://github.com/mscfd/emacs-f90-ts-mode/issues

Notes:
- Emacs 31 supports 0.26, and the mode runs in both configurations.
- Emacs 30.x must be linked against tree-sitter 0.25.x at runtime.
- Emacs 29 support has been tested with treesitter 0.20.8.
For details see MANUAL at https://github.com/mscfd/emacs-f90-ts-mode