Found when parsing `Lib/test/test_coroutines.py` using the new parser.
For whatever reason, having `await` be an `expression` (with an argument
of the same kind) resulted in a bad parse. Consulting the official
grammar, we see that `await` should actually be a `primary_expression`
instead. This is also more in line with the other unary operators, whose
precedence is shared by the `await` syntax.
Quoting the Python documentation (last paragraph of
https://docs.python.org/3/reference/lexical_analysis.html#escape-sequences):
"Even in a raw literal, quotes can be escaped with a backslash, but the
backslash remains in the result; for example, r"\"" is a valid string
literal consisting of two characters: a backslash and a double quote;
r"\" is not a valid string literal (even a raw string cannot end in an
odd number of backslashes)."
We did not handle this correctly in the scanner, as we only consumed the
backslash but not the following single or double quote, resulting in
that character getting interpreted as the end of the string.
To fix this, we do a second lookahead after consuming the backslash, and
if the next character is the end character for the string, we advance
the lexer across it as well.
Similarly, backslashes in raw strings can escape other backslashes.
Thus, for a string like '\\' we must consume the second backslash,
otherwise we'll interpret it as escaping the end quote.
A somewhat complicated solution that necessitated adding a new custom
function to `tsg-python`. See the comments in `python.tsg` for why this
was necessary.
Surprisingly, the new parser did not support these constructs (and the
relevant test was missing this case), so on files that required the new
parser we were unable to parse this construct.
To fix it, we add `list_pattern` (not to be confused with
`pattern_list`) as a `tree-sitter-python` node that results in a `List`
node in the AST.
Turns out, `except*` is actually not a token on its own according to the
Python grammar. This means it's legal to write `except *foo: ...`, which
we previously would consider a syntax error.
To fix it, we simply break up the `except*` into two separate tokens.
That is, the `*T` in `def foo(*args : *T): ...`.
This is apparently a piece of syntax we did not support correctly until
now.
In terms of the grammar, we simply add `list_splat` as a possible
alternative for `type` (which could previously only be an `expression`).
We also update `python.tsg` to not specify `expression` those places (as
the relevant stanzas will then not work for `list_splat`s).
This syntax is not supported by the old parser, hence we only add a new
parser test for it.
This is primarily useful for ensuring that errors where a node does not
have an appropriate context set in `python.tsg` actually have an effect
on the pass/fail status of the parser tests. Previously, these would
just be logged to stdout, but test could still succeed when there were
errors present.
Also fixes one of the logging lines in `tsg_parser.py` to be more
consistent with the others.
On Windows, make's path resolution algorithm is incorrect.
It picks up a bazel.exe in PATH that's _after_ a bazel binary.
In particular, on actions, the non-exe binary is a bazelisk
instance, whereas bazel.exe is a bazel (at the current time 7.3.2)
installation.
This means we pick up the wrong bazel version, and
if the differences between the bazel we want and that we actually
get are too big, the build fails.
