Better error for min_success_ratio<1

[pingsutw]

Tracking issue

NA

Why are the changes needed?

when min_success_ratio < 1, flytekit automatically makes the output interface optional (str => Optional[str])
If the input of the downstream task is not optional, Flytekit will fail to deserialize the output and display a confusing error message

What changes were proposed in this pull request?

check the type at compile time

How was this patch tested?

Setup process

pyflyte run flyte-example/map_optional_list.py wf

import os
import tempfile
from typing import List

from flytekit import map_task, workflow, task
from flytekit.types.directory import FlyteDirectory


@task
def generate_directory(word: str) -> FlyteDirectory:
    temp_dir1 = tempfile.TemporaryDirectory()
    with open(os.path.join(temp_dir1.name, "file.txt"), "w") as tmp:
        tmp.write(f"Hello world {word}!\n")
    return FlyteDirectory(path=temp_dir1.name)


@task
def consume_directories(dirs: List[FlyteDirectory]):
    for d in dirs:
        print(f"Directory: {d.path} {d._remote_source}")
        for path_info, other_info in d.crawl():
            print(path_info)


mt = map_task(generate_directory, min_success_ratio=0.1)


@workflow
def wf():
    dirs = mt(word=["one", "two", "three"])
    consume_directories(dirs=dirs

Screenshots

Before:

After:

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

NA

Docs link

NA

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 15 lines in your changes missing coverage. Please review.

Project coverage is 48.31%. Comparing base (8bad8e6) to head (f18b84d).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
flytekit/core/promise.py	0.00%	14 Missing ⚠️
flytekit/core/type_engine.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2724      +/-   ##
==========================================
- Coverage   49.76%   48.31%   -1.45%     
==========================================
  Files         193      279      +86     
  Lines       19659    24057    +4398     
  Branches     4097     2844    -1253     
==========================================
+ Hits         9783    11624    +1841     
- Misses       9345    12220    +2875     
+ Partials      531      213     -318     

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[wild-endeavor]

nix this

[wild-endeavor]

oh this won't run nm, keep

[wild-endeavor]

i think it's good to have this... i don't want flytekit to fall into the trap of duplicating the compiler, but this is a common and tricky enough case that I think it's okay to explicitly catch this.