Once you have compiled the dynamic library for your custom language, you need to register it in the `sgconfig.yml` file.

You need to add a new entry under the `customLanguages` key with the name of your custom language and some properties:

For example, to search for all occurrences of `print` in mojo files, you can run:

Or you can write a rule in yaml like this:

ast-grep has builtin support to search JavaScript and CSS inside HTML files.

Suppose we have an HTML file like below:

Running this ast-grep command will extract the matching CSS style code out of the HTML file!

ast-grep outputs this beautiful CLI report.

ast-grep works well even if just providing the pattern without specifying the pattern language!

You can also use ast-grep's [rule file](https://ast-grep.github.io/guide/rule-config.html) to search injected languages.

message: Prefer use appropriate custom UI instead of obtrusive alert call.

You can search the CSS inside JavaScript in the project configuration folder using this command:

It will produce the match result:

ast-grep has two ways to configure pattern strictness.

2. Using `strictness` in Pattern Object

Compared to the other two tools, ast-grep is lesser-known. In short it can do search and replace based on [abstract syntax trees](https://www.wikiwand.com/en/Abstract_syntax_tree). You can install it via [`cargo`](https://crates.io/crates/ast-grep) or [`brew`](https://formulae.brew.sh/formula/ast-grep).

cargo install ast-grep

brew install ast-grep

We need to provide a pattern, `-p`, for it to search as well as a rewrite string, `-r` to replace the old API with the new one. The command should be quite self-explanatory.

We suggest to add `-i` flag for `--interactive` editing. ast-grep will display the changed code diff and ask your decision to accept or not.

The command:

3. `SystemStage`

Let's write a command for this code migration.

-p '$APP.add_stage_after($STAGE, $OWN_STAGE, SystemStage::parallel())' \

-r '$APP.configure_set($OWN_STAGE.after($STAGE))' -i

However, I found some `add_stage_after`s are not replaced. Nah, ast-grep is [quite dumb](https://github.com/ast-grep/ast-grep/issues/374) that it cannot handle the optional comma after the last argument. So I used another query with a trailing comma.

-p 'app.add_stage_after($STAGE, $OWN_STAGE, SystemStage::parallel(),)' \

-r 'app.configure_set($OWN_STAGE.after($STAGE))' -i

Let's also write a pattern for it.

-p '$APP.add_system_to_stage($STAGE, $SYS)' \

-r '$APP.add_system($SYS.in_base_set($STAGE))' -i

Another change is to use `add_systems` instead of `add_system_set`. This is a simple pattern!

-p '$APP.add_system_set_to_stage($STAGE, $SYS,)' \

-r '$APP.add_systems($SYS.in_set($STAGE))' -i

* ast-grep’s YAML rule now has a new `transform` rule: `conversion`, which can change matches to different cases, such as upper, lower, or camelcase.

* ast-grep’s diff/rewriting now can fix multiple rules at once. See [commit](https://github.com/ast-grep/ast-grep/commit/2b301116996b7b010ed271672d35a3529fb36e56)

* ast-grep now prints matches with context like `grep -A -B -C`. See [issue](https://github.com/ast-grep/ast-grep/issues/464)

* JSON schema is added for better YAML rule editing. See [folder](https://github.com/ast-grep/ast-grep/tree/main/schemas)

* ast-grep now has official github action setup! See [action](https://github.com/ast-grep/action)

* Add python api support to allow users to write custom scripts using ast-grep. See [issue](https://github.com/ast-grep/ast-grep/issues/389)

* Support global language config to let users specify default options for each language. See [issue](https://github.com/ast-grep/ast-grep/issues/658)

* Improve napi documentation to help users understand how to use the native node module of ast-grep. See [issue](https://github.com/ast-grep/ast-grep/issues/682)

* Add ast-grep’s pattern/rule tutorial to teach users how to write effective and efficient patterns and rules for ast-grep. See [issue](https://github.com/ast-grep/ast-grep.github.io/issues/154)

* Add examples to ast-grep’s reference page to illustrate the usage and functionality of each option and feature. See [issue](https://github.com/ast-grep/ast-grep.github.io/issues/266)

* You can now use [`--inline-rules`](https://ast-grep.github.io/reference/cli/scan.html#inline-rules-rule-text) to run rules without creating any files on your disk! You can pass everything, pattern/rule/input, as a string. This is great for scripting!

* [`--stdin`](https://ast-grep.github.io/reference/cli/run.html#stdin) will always wait for your input so you can match some code written in your terminal.

* We have added support for three new languages: bash, php and elixir.

- **Tree-Sitter Version Bump**: We've upgraded to the latest tree-sitter version, enhancing parsing accuracy and speed. In future releases, we plan to leverage tree-sitter's [new Web Assembly grammar](https://zed.dev/blog/language-extensions-part-1) to support even more languages.

- **Scan and Diff Merge**: The [refactor](https://github.com/ast-grep/ast-grep/commit/c78299d2902662cd98bda44f3faf3fbc88439078) combines `CombinedScan::scan` and `CombinedScan::diff` for a more streamlined process.

language: JavaScript # please fully spell the language

playgroundLink: '[TODO]'

hasFix: true

ruleType: 'pattern' # 'pattern' or 'yaml'

-r '$A.char_indices()' \

-l rs