This blog post details how to implement custom syntax highlighting in Emacs using tree-sitter. The author demonstrates creating a minor mode for highlighting TODO items and FIXMEs in comments within C++ code. This involves defining specific queries that target the comment nodes in the tree-sitter parse tree and then associating faces (colors and styles) with the captured nodes. The example provides a practical illustration of leveraging tree-sitter's structured code understanding to achieve more precise and context-aware highlighting than traditional regular expression-based approaches. The post also briefly covers how to incorporate these queries into a theme for broader application and includes a troubleshooting tip for ensuring tree-sitter highlighting is active.
Amit Patel's blog post, "Emacs Tree-sitter Custom Highlighting," explores leveraging the power of tree-sitter, a parsing library, for granular and context-aware syntax highlighting within Emacs. He begins by highlighting the limitations of traditional regular expression-based highlighting, noting its struggles with complex language constructs and the potential for slowdowns due to backtracking. Tree-sitter, in contrast, parses the code into an abstract syntax tree, allowing for more precise and efficient highlighting based on the actual structure of the code.
Patel meticulously details the process of setting up tree-sitter in Emacs, including the installation of necessary packages and configuration steps. He then delves into the core of the post: customizing highlighting rules. He explains how to define custom "queries" using tree-sitter's query language. These queries effectively target specific nodes in the parsed syntax tree, enabling the application of distinct highlighting styles. He provides concrete examples demonstrating how to highlight function calls, variable declarations, and even specific keywords within different contexts.
He emphasizes the flexibility and expressiveness of tree-sitter queries, showcasing how they can match patterns based not just on node types but also on their relationships within the tree, enabling highly specific highlighting scenarios. He illustrates this with an example of highlighting the self parameter in Python methods. Patel also covers handling language-specific configurations and ensuring smooth integration with existing Emacs themes.
Furthermore, Patel explores more advanced usage, such as highlighting based on capture groups within queries and dynamically updating the highlighting as the code is modified. He acknowledges the initial complexity of learning the tree-sitter query language but argues that its power and precision justify the effort. He concludes by expressing his enthusiasm for the potential of tree-sitter to significantly enhance the code editing experience in Emacs. He encourages readers to explore the possibilities and contribute to the growing ecosystem of tree-sitter grammars and highlighting configurations.
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https://news.ycombinator.com/item?id=43217195
HN commenters largely praised the integration of tree-sitter into Emacs, highlighting the significant improvements in syntax highlighting accuracy and performance. Some expressed excitement over the potential for more advanced features like semantic highlighting and code navigation enabled by tree-sitter's deeper understanding of code structure. A few users shared their personal experiences with setting up and using tree-sitter in Emacs, offering tips and workarounds for common issues. One commenter noted the wider adoption of tree-sitter across various editors and its positive impact on the developer experience. Others discussed the technical details of tree-sitter's implementation, comparing it to traditional regular expression-based highlighting. A couple of comments touched on the potential for future improvements, such as asynchronous parsing and better support for more obscure languages.
The Hacker News post "Emacs Tree-sitter custom highlighting" discussing Amit Patel's blog post about the same topic has generated several comments. Many users express excitement and appreciation for the advancements in syntax highlighting offered by tree-sitter integration within Emacs.
Several commenters discuss the performance improvements and accuracy of tree-sitter parsing compared to traditional regular expression-based highlighting. One user points out that tree-sitter is particularly beneficial for languages with complex grammars, where regex-based highlighting often struggles. They specifically mention JavaScript as an example.
Another commenter praises the ability to highlight based on semantic understanding, enabling features like highlighting all variables of a specific type within a scope. This is highlighted as a significant improvement over purely syntactic highlighting.
Some discussion revolves around the installation and configuration of tree-sitter in Emacs. One user asks for clarification on the setup process, and another provides helpful links and tips for getting started.
A few comments mention other text editors and IDEs that have already adopted tree-sitter, highlighting its growing popularity and effectiveness. One user mentions its use in Neovim, and another points to its origins within Atom.
The overall sentiment in the comments is positive, with many users excited about the potential of tree-sitter to enhance the Emacs editing experience. Several express their intent to try out the new features and contribute to its development. The improvements to accuracy, performance, and the ability for semantic highlighting are repeatedly lauded.