Api for registering custom languages (#43)

* Api for registering custom languages

May not be the best, but it works :}

Allows registering a custom wasm with a custom language id
Can overwrite the built in languages
Can register a custom language id with one of the built in wasms


#34 (comment)

* Reload documents corresponding to the language id

* Revert `let languages = { }` back to `const`

* const => let

Co-authored-by: Pokey Rule <[email protected]>

* find => some

Co-authored-by: Pokey Rule <[email protected]>

* Parsing a Custom language

* Remove `const` on ` absolute`

* Remove ability to overwrite languages

* `wasm` => `wasmPath`

* Update README.md

* I assume this is what you mean by exception

* Improve documentation

* More tweaks

Co-authored-by: Pokey Rule <[email protected]>

Author: RedCMD

README.md

@@ -1,7 +1,10 @@
 # Parse tree
 
-Exposes an api function that can be used to get a parse tree node for a given
-file location. Can be used as follows:
+Exposes an api function that can be used to get a parse tree node for a given file location.
+
+## Usage
+
+Can be used as follows:
 
 ```ts
 const parseTreeExtension = vscode.extensions.getExtension("pokey.parse-tree");
@@ -13,10 +16,22 @@ if (parseTreeExtension == null) {
 const { getNodeAtLocation } = await parseTreeExtension.activate();
 ```
 
-Don't forget to add add an `extensionDependencies`-entry to `package.json` as
+Don't forget to add an `extensionDependencies`-entry to `package.json` as
 described in
 https://code.visualstudio.com/api/references/vscode-api#extensions.
 
+### Parsing a custom language
+
+If you'd like to add support for a new language, see the [Adding a new language](#adding-a-new-language) section below. Alternatively, your extension can register a custom language with this extension. Although this is not the preferred way to add a new language, it can be convenient when you have a parser that you don't believe belongs in the main extension.
+
+Parsing your own language is as simple as registering your `languageId` with an absolute path to your `.wasm` file:
+
+```ts
+const { registerLanguage } = await parseTreeExtension.activate();
+
+registerLanguage(languageId, wasmPath);
+```
+
 ## Contributing
 
 ### Setup
@@ -49,9 +64,9 @@ When working with WSL, the host vscode instance connects to a vscode server on t
 We build a custom version of `web-tree-sitter` to ensure that we can always use the latest version and fix any problems as they come up.
 To update `web-tree-sitter`:
 
-  1. Update the variable `TREE_SITTER_VERSION` in the [`Makefile`](Makefile#L8);
-  2. Update the path to `web-tree-sitter` in [`package.json`](package.json#103);
-  3. (Optional) Create a new patch in `patches/tree-sitter+$TREE_SITTER_VERSION.patch`.
+1. Update the variable `TREE_SITTER_VERSION` in the [`Makefile`](Makefile#L8);
+2. Update the path to `web-tree-sitter` in [`package.json`](package.json#103);
+3. (Optional) Create a new patch in `patches/tree-sitter+$TREE_SITTER_VERSION.patch`.
 
 The script which builds our custom version is in the [`Makefile`](Makefile#L37-63).
 

src/extension.ts

@@ -70,11 +70,17 @@ export async function activate(context: vscode.ExtensionContext) {
       return true;
     }
 
-    const absolute = path.join(
-      context.extensionPath,
-      "parsers",
-      language.module + ".wasm"
-    );
+    let absolute;
+    if (path.isAbsolute(language.module)) {
+      absolute = language.module;
+    } else {
+      absolute = path.join(
+        context.extensionPath,
+        "parsers",
+        language.module + ".wasm"
+      );
+    }
+
     const wasm = path.relative(process.cwd(), absolute);
     const lang = await Parser.Language.load(wasm);
     const parser = new Parser();
@@ -226,6 +232,23 @@ export async function activate(context: vscode.ExtensionContext) {
   return {
     loadLanguage,
 
+    /**
+     * Register a parser wasm file for a language not supported by this
+     * extension. Note that {@link wasmPath} must be an absolute path, and
+     * {@link languageId} must not already have a registered parser.
+     * @param languageId The VSCode language id that you'd like to register a
+     * parser for
+     * @param wasmPath The absolute path to the wasm file for your parser
+     */
+    registerLanguage(languageId: string, wasmPath: string) {
+      if (languages[languageId] != null) {
+        throw new Error(`Language id '${languageId}' is already registered`);
+      }
+
+      languages[languageId] = { module: wasmPath };
+      colorAllOpen();
+    },
+
     getTree(document: vscode.TextDocument) {
       return getTreeForUri(document.uri);
     },