Bug in lib/time: time.parse_time can't support format like Python

[fanconnie]

Errors for format=RFC3339 or %Y-%m-%dT%H:%M:%S.%f

>>> print("time.parse_time():", time.parse_time("2021-03-22T23:20:50.52Z"))
time.parse_time(): 2021-03-22 23:20:50.52 +0000 UTC
>>> print("time.parse_time():", time.parse_time("2023-08-22T23:20:50.52Z"))
time.parse_time(): 2023-08-22 23:20:50.52 +0000 UTC
>>> print("time.parse_time():", time.parse_time("2023-08-22T23:20:50.52Z", format="RFC3339"))
Traceback (most recent call last):
  <stdin>:1:44: in <expr>
Error in parse_time: parsing time "2023-08-22T23:20:50.52Z" as "RFC3339": cannot parse "2023-08-22T23:20:50.52Z" as "RFC"
>>> print("time.parse_time():", time.parse_time("2023-08-22T23:20:50.52Z", format='%Y-%m-%dT%H:%M:%S.%f'))
Traceback (most recent call last):
  <stdin>:1:44: in <expr>
Error in parse_time: parsing time "2023-08-22T23:20:50.52Z" as "%Y-%m-%dT%H:%M:%S.%f": cannot parse "2023-08-22T23:20:50.52Z" as "%Y-%m-%dT%H:%M:%S.%f"
>>>

[SamWheating]

I don't think that this qualifies as a bug, as this is by design. The comments in the implementation specify that parse_time expects a golang-style timestamp format:

starlark-go/lib/time/time.go

Lines 32 to 36 in dded032

	// parse_time(x, format, location) - Parses the given time string using a specific time format and location.
	// The expected arguments are a time string (mandatory), a time format
	// (optional, set to RFC3339 by default, e.g. "2021-03-22T23:20:50.52Z")
	// and a name of location (optional, set to UTC by default). For more details,
	// refer to https://pkg.go.dev/time#Parse and https://pkg.go.dev/time#ParseInLocation.

So the literal string "RFC3339" isn't going to work either, but fortunately the default format to parse_time is the golang-style format string for an RFC3339 timestamp ("2006-01-02T15:04:05Z07:00")

[adonovan]

This package exists only in the Go implementation. In hindsight exposing this very Go-centric API for time formatting was perhaps a mistake, and if other implementations (Java, Rust) were to want a time package we should probably revisit it.

[fanconnie]

This package exists only in the Go implementation. In hindsight exposing this very Go-centric API for time formatting was perhaps a mistake, and if other implementations (Java, Rust) were to want a time package we should probably revisit it.

OK:

bazelbuild/bazel#19477

facebook/starlark-rust#95