misc: Add a guide to update grammars (#1079)

README.md

@@ -80,6 +80,11 @@ cargo insta test --review
 
 Will run the tests, generate the new snapshot references and let you review them.
 
+### Updating grammars
+Have a look at
+<a href="https://mozilla.github.io/rust-code-analysis/developers/update-grammars.html" target="_blank">Update grammars guide</a>
+to learn how to update languages grammars.
+
 # Contributing
 
 If you want to contribute to the development of this software, have a look at the

rust-code-analysis-book/src/SUMMARY.md

@@ -10,3 +10,4 @@
 - [Developers Guide](developers/README.md)
     - [How-to: Add a new language](developers/new-language.md)
     - [How-to: Implement LoC](developers/loc.md)
+    - [How-to: Update grammars](developers/update-grammars.md)

rust-code-analysis-book/src/developers/update-grammars.md

@@ -0,0 +1,60 @@
+# Update grammars
+
+Each programming language needs to be parsed in order to extract its syntax and semantic: the so-called grammar of a language.
+In `rust-code-analysis`, we use [tree-sitter](https://github.com/tree-sitter) as parsing library since it provides a set of distinct grammars for each of our
+supported programming languages. But a grammar is not a static monolith, it changes over time, and it can also be affected by bugs,
+hence it is necessary to update it every now and then.
+
+As now, since we have used `bash` scripts to automate the operations, grammars can be updated natively **only** on `Linux` and `MacOS` systems, but these scripts can also run on `Windows` using `WSL`.
+
+In `rust-code-analysis` we use both **third-party** and **internal** grammars.
+The first ones are published on `crates.io` and maintained by external developers,
+while the second ones have been thought and defined inside the project to manage variant of some languages
+used in `Firefox`.
+We are going to explain how to update both of them in the following sections.
+
+## Third-party grammars
+
+Update the grammar version in `Cargo.toml` and `enums/Cargo.toml`. Below an example for the `tree-sitter-java` grammar
+
+```toml
+tree-sitter-java = "x.xx.x"
+```
+where `x` represents a digit.
+
+Run `./recreate-grammars` to recreate and refresh all grammars structures and data
+
+```bash
+./recreate-grammars
+```
+
+Once the script above has finished its execution, you need to fix, if there are any, all failed tests and problems
+introduced by changes in the grammars.
+
+Commit your changes and create a new pull request
+
+## Internal grammars
+
+Update dependency `version` field in `Cargo.toml` and `enums/Cargo.toml`. Below an example for the `tree-sitter-ccomment` grammar
+
+```toml
+tree-sitter-ccomment = { path = "./tree-sitter-ccomment", version = "=x.xx.x" }
+```
+where `x` represents a digit.
+
+Open the `Cargo.toml` file of the chosen grammar and:
+ - Set its version to the **same** value present in the main `Cargo.toml` file
+ - Increase the `tree-sitter` version to the most recent one
+
+Run `./generate-grammars/generate-grammar.sh` which updates the grammar recreating and refreshing every file and script.
+This script requires the name of the grammar as mandatory argument.
+Below an example always using the `tree-sitter-ccomment` grammar
+
+```bash
+./generate-grammars/generate-grammar.sh tree-sitter-ccomment
+```
+
+Once the script above has finished its execution, you need to fix, if there are any, all failed tests and problems
+introduced by changes in the grammars.
+
+Commit your changes and create a new pull request