Support inline # comments on TypedDict and dataclass fields

[Hemanth Dhanasekaran (hemanth1999k)]

Fixes#242.

Currently the only way to document a field is the verbose Annotated[int, Doc("...")] syntax. This adds support for native Python inline comments:

classPoint(TypedDict):
x: int# X-coordinatey: int# Y-coordinate

which produces the same TypeScript as before:

interfacePoint{// X-coordinatex: number;// Y-coordinatey: number;}

Uses inspect.getsourcelines + ast to pull # comments off field definitions at schema-generation time. Annotated/Doc still takes priority when both are present. Fails silently for dynamically-defined types (REPL, exec, etc.) so nothing breaks.

Adds three snapshot tests covering TypedDict inline comments, Doc-takes-priority, and dataclass inline comments.

[Hemanth Dhanasekaran (hemanth1999k)]

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[Hemanth Dhanasekaran (hemanth1999k)]

@microsoft-github-policy-service agree

[robgruen]

I really like the idea of this PR. Having inline comments would be fantastic. However, I noted a few different schemas that could break the implementation as provided. Instead of doing a find string, use the Python tokenizer to get each raw AST token and then grab the contents of the comment token.

Here's a suggestion from copilot (requires importing io & tokenize):

def_extract_inline_field_comments(py_type: type) ->dict[str, str]:
"""Return a mapping of field name -> trailing '#' comment for a TypedDict/dataclass."""try:
source_lines, _=inspect.getsourcelines(py_type)
except (OSError, TypeError):
# Source unavailable (e.g. dynamically created types) -> no comments.return {}
source=textwrap.dedent("".join(source_lines))
# Only real COMMENT tokens count. A '#' inside "..." is a STRING token, so it's ignored.comment_by_line: dict[int, str] = {}
try:
fortokenintokenize.generate_tokens(io.StringIO(source).readline):
iftoken.type==tokenize.COMMENT:
comment_by_line[token.start[0]] =token.string[1:].strip()
except (tokenize.TokenError, IndentationError):
pass# keep whatever we gathered before an incomplete-source errorifnotcomment_by_line:
return {}
try:
tree=ast.parse(source)
exceptSyntaxError:
return {}
comments: dict[str, str] = {}
fornodeinast.walk(tree):
ifisinstance(node, ast.ClassDef):
forstmtinnode.body:
if (
isinstance(stmt, ast.AnnAssign)
andisinstance(stmt.target, ast.Name)
andstmt.end_linenoisnotNone
):
comment=comment_by_line.get(stmt.end_lineno)
ifcomment:
comments[stmt.target.id] =commentreturncomments

[robgruen]

This will cause problems....see these schemas that break:

# BREAK 1 — hex colors, NO comment intendedclassTheme(TypedDict):
background: Literal["#FFFFFF", "#000000"]
accent: Literal["#FF0000"]
# BREAK 2 — real comment gets corrupted (string '#' comes first)classSwatch(TypedDict):
color: Literal["#00FF00"] # the accent color as a hex triplet# BREAK 3 — dataclass default@dataclassclassGitConfig:
comment_marker: str="value # not a comment"# BREAK 4 — URL fragment in a default leaks out@dataclassclassApiEndpoint:
url: str="https://api.example.com/v1/items#latest"# BREAK 5 — multi-line annotation whose last line has '#' in a stringclassButtonSpec(TypedDict):
variant: Literal[
"primary",
"hash-#-danger"] # pick one variant