Support for tags about test HOT 6 CLOSED

I did some thinking about this, and here's how I envision it working:

Tags are defined in roughly the same manner as other metadata. For example,

@Tag("awesome")

void main() {
  group("a neat group", () {
    test("a fun test", () {
      // ...
    }, tag: ["fun", "cool"]);
  }, tag: "neat");
}

Alternately, we could say that tag: always takes a string and that the string is comma-separated for multiple tags. Tags can be arbitrary strings, but to catch typos, they must be declared in the config file (#46):

tags:
  awesome:
  fun:
  cool:
  neat:

Tags can be used from the command-line with the --exclude and --include (--only?) flags, which specify which tags not to run or to run exclusively, respectively.

Tags can also have metadata associated with them in the configuration file. This metadata applies to all tests with that tag. For example:

tags:
  slow: {timeout: 2x}
  ie: {test_on: windows}
  git:
    on_platform:
      windows: {timeout: 2x}

Tags can also be configured differently for different presets (#83). For example:

presets:
  travis:
    tags: {ie: {skip: true}}

from test.

Looks great. I would use --tags and --exclude-tags.

from test.

That sounds fine.

from test.

Tags can be arbitrary strings, but to catch typos, they must be declared in the config file

Failing to do this should produce a warning. We should also allow tags that are specified on the command-line even if they're not in the config file, to support short-term tags like "solo".

from test.

Another thought: the --tags parameter should support the full platform-selector syntax so that users can express complex constraints like "run all fast isolate tests that don't use IO" (as --tags "fast && browser && !io"). This has the side effect of requiring that all tags be representable as Dart identifiers, but I don't think that's onerous.

--tags a,b,c would still work—it would be equivalent to --tags "(a) && (b) && (c)". Similarly, --exclude-tags a,b,c would be equivalent to !(a) && !(b) && !(c).

from test.

Initial configuration file support has landed, so this is no longer blocked.

from test.