Add command for source formatting

README.md

@@ -2,11 +2,12 @@
 Stack-based language, like forth.
 
 ### Contents
-The following tools for the Aaa language can be found is this repo
+The following tools for the Aaa language can be found is this repository:
 * A [tokenizer](./aaa/tokenizer/) and [parser](./aaa/parser/) for Aaa.
 * A [type checker](./aaa/type_checker/)
 * A [transpiler to Rust](./aaa/transpiler/)
 * A [VS Code extension](./aaa-vscode-extension/README.md) for the Aaa language.
+* A [formatter](./aaa/formatter.py) for Aaa source files.
 * A lot of tests, written both in python and Aaa
 
 ### Examples
@@ -85,6 +86,26 @@ Now you can start running code in Aaa or develop the language!
 
 To enable syntax highlighting for VS Code, enable the [Aaa language extension](./aaa-vscode-extension/README.md)
 
+### Setup format on save
+For VS Code follow these steps:
+* Install the [Run on Save](https://marketplace.visualstudio.com/items?itemName=pucelle.run-on-save) extension.
+* Merge the JSON configuration below into your `*.code-workspace` JSON file.
+
+```json
+{
+    "settings": {
+        "runOnSave.commands": [
+			{
+				"match": ".*\\.aaa$",
+				"command": "cd ${workspaceFolder} && pdm run ./manage.py format --stdlib-path ./stdlib ${file} --fix",
+				"runIn": "backend",
+				"runningStatusMessage": "Formatting ${fileBasename}",
+				"finishStatusMessage": "${fileBasename} was formatted"
+			},
+		]
+    }
+}
+```
 
 ### Aaa and porth
 After watching part of the [Youtube series](https://www.youtube.com/playlist?list=PLpM-Dvs8t0VbMZA7wW9aR3EtBqe2kinu4) on [porth](https://gitlab.com/tsoding/porth), I wanted to make my own stack-based language. Aaa and porth have some similarities, but obviously are not compatible with each other. No code was copied over from the porth repo.

aaa/__init__.py

@@ -1,3 +1,4 @@
+import os
 import secrets
 from pathlib import Path
 from tempfile import gettempdir
@@ -64,6 +65,22 @@ class AaaException(Exception):
     ...
 
 
+class AaaEnvironmentError(AaaException):
+    ...
+
+
+def get_stdlib_path() -> Path:
+    try:
+        stdlib_folder = os.environ["AAA_STDLIB_PATH"]
+    except KeyError as e:
+        raise AaaEnvironmentError(
+            "Environment variable AAA_STDLIB_PATH is not set.\n"
+            + "Cannot find standard library!"
+        ) from e
+
+    return Path(stdlib_folder) / "builtins.aaa"
+
+
 AAA_DEFAULT_OUTPUT_FOLDER_ROOT = Path(gettempdir()) / "aaa/transpiled"
 AAA_TEST_OUTPUT_FOLDER_ROOT = Path(gettempdir()) / "aaa/transpiled/tests"
 

aaa/cross_referencer/cross_referencer.py

@@ -744,7 +744,9 @@ def run(self) -> FunctionBody:
     def _resolve_function_body(self, parsed_body: parser.FunctionBody) -> FunctionBody:
         return FunctionBody(
             items=[
-                self._resolve_function_body_item(item) for item in parsed_body.items
+                self._resolve_function_body_item(item)
+                for item in parsed_body.items
+                if type(item) != parser.Comment
             ],
             parsed=parsed_body,
         )
@@ -856,7 +858,7 @@ def _resolve_function_body_item(
             parser.WhileLoop: self._resolve_while_loop,
         }
 
-        assert set(resolve_functions.keys()) == set(parser.FunctionBodyItem.__args__)  # type: ignore
+        assert set(resolve_functions.keys()) == set(parser.FunctionBodyItem.__args__) - {parser.Comment}  # type: ignore
         return resolve_functions[type(parsed_item)](parsed_item)
 
     def _resolve_function_pointer_literal(