[dart-misc] Recommendations for when to use import prefixes, esp wi/ lower-case constants

['Samuel Rawlins' via Dart Misc]

Hey Dartisans (+Bob for Effective Dart comments),

It is common to import packages with many top-level constants and functions
with a prefix, e.g.

import 'dart:math' as math;
import 'package:path/path.dart' as p;

void main() {
print(math.sqrt(2));
print(p.join('foo', 'bar'));
}

And I didn't use to import dart:convert with a prefix, because I use
classes (like JsonDecoder). However, with all constants now lower-case in
Dart 2, I think I want to start importing libraries such as dart:convert
with a prefix, maybe even with show directives.

Another reason is that these lower-case constants clutter up the scope with
things that look like local variables I never declared.

WDUT?

import 'dart:convert';
void main() {
print(ascii.decode([97, 98, 99])); // Wait, where did I declare an
`ascii` variable?
var manyJsonDocuments = getDocs();
for (json in manyJsonDocuments) { // I accidentally forgot `var`, but
now get a weird error about reassigning a constant?
...
}
}

import 'dart:convert' as convert;
void main() {
print(convert.ascii.decode(...));
}

import 'dart:convert' show ascii;
void main() {
print(ascii.decode(...)); // still not super obvious where ascii came
from but... you can scroll up to imports and its in your face.
}

// or both prefixed and show?

['Bob Nystrom' via Dart Misc]

This is an interesting one.

Post by 'Samuel Rawlins' via Dart Misc
Hey Dartisans (+Bob for Effective Dart comments),
It is common to import packages with many top-level constants and
functions with a prefix, e.g.
import 'dart:math' as math;
import 'package:path/path.dart' as p;
void main() {
print(math.sqrt(2));
print(p.join('foo', 'bar'));
}

Right. The way I think of it is any given library is usually either
designed to be imported with a prefix or not. If it's top-level names are
fairly unique, it's usually intended to be unprefixed. If they are very
short, the author usually intends you to prefix. The path package is a good
example of the latter.

Post by 'Samuel Rawlins' via Dart Misc
And I didn't use to import dart:convert with a prefix, because I use
classes (like JsonDecoder). However, with all constants now lower-case in
Dart 2, I think I want to start importing libraries such as dart:convert
with a prefix, maybe even with show directives.
Another reason is that these lower-case constants clutter up the scope
with things that look like local variables I never declared.

Yeah, "dart:convert" is in a weird limbo. I think with the initial all caps
constants, it made sense to use it without a prefix since those names are
less likely to collide. But it feels a little weird to import unprefixed
top-level names like "json".

There was some concern about this, which is why there are top-level
function jsonDecode() and jsonEncode().

But, yeah, it's a little weird. Personally, I still import it unprefixed
and it seems to work out OK.

– bob