tree-sitter-fortran

tree-sitter-fortran is the Fortran grammar for Tree-sitter, the incremental parsing library that underpins syntax highlighting and code intelligence in modern editors. It compiles Fortran source into a concrete syntax tree that can be re-parsed efficiently as the document changes, providing the structural foundation for highlighting, folding, navigation, and analysis. It covers fixed- and free-form Fortran source and is maintained by the Fortran tooling community.

The grammar ships with prebuilt bindings for Rust, C, Node.js, Python, Go, and Swift, so the same parser can be embedded in editors, language servers, and static-analysis pipelines regardless of host language.

What You Get

• A complete Fortran grammar (grammar.js) plus the generated C parser (src/parser.c) ready to compile
• Rust bindings exposing the parser through the tree-sitter-language interface
• Additional bindings for C, Node.js, Python, Go, and Swift from a single grammar source
• Highlight and query files (queries/) for syntax highlighting and code navigation
• A corpus test suite exercising the grammar’s constructs and error recovery

Common Use Cases

• Powering syntax highlighting for Fortran in code editors and terminal viewers
• Building language servers and linters that need a structured view of Fortran code
• Enabling code folding, structural selection, and outline views for Fortran files
• Extracting or transforming Fortran content programmatically via the syntax tree

Under The Hood

Architecture - The grammar is declared in grammar.js using Tree-sitter’s JavaScript DSL, defining Fortran’s syntactic constructs with extras for whitespace and comments and, where needed, externals for context-sensitive tokens resolved by a custom scanner. The Tree-sitter CLI compiles this into a deterministic C parser (src/parser.c) that host bindings load at runtime. Tech Stack - The source of truth is the JavaScript grammar DSL; the generated parser is C. The Rust binding depends on tree-sitter-language and compiles the generated parser via a cc-based build script, exposing a LANGUAGE constant. Parallel bindings for C, Node.js, Python, Go, and Swift are generated from the same grammar. Code Quality - Correctness is anchored by Tree-sitter’s corpus test format (input snippets paired with expected S-expression trees) plus highlight fixtures, and CI runs on GitHub Actions. The generated parser is machine-produced and never hand-edited, so quality tracks the grammar definition and its tests. API Design - Integration is minimal: consumers pass the language’s exported LANGUAGE entry point to a Tree-sitter parser instance in their host language, so adding Fortran parsing to an editor or tool takes only a few lines once the Tree-sitter runtime is present.