assert: ensure message is always displayed & fix under bazel

[cstrahan]

Note that I still need to run the tests, but I wanted to get this PR open ASAP.

This PR fixes #274.

Now, when running under bazel test we'll see the following sort of error message when the target test source file can't be found:

--- FAIL: TestAssertShouldWorkUnderBazel (0.00s)
    your_test.go:40: the test source file does not exist: /private/var/tmp/_bazel_charles/99cf13450b07a7c7594bbbe785fbd4ef/sandbox/darwin-sandbox/20/execroot/__main__/bazel-out/darwin_arm64-fastbuild/bin/some_package/your_package_test_/your_package_test.runfiles/__main__/some_package/your_test.go
        it appears that you are running this test under Bazel (target: //some_package:your_package_test);
        check that your test source files are added as test data in your go_test targets.
        example:
            go_test(
                name = "your_package_test",
                     srcs = ["your_test.go"],
                     deps = ["@tools_gotest_v3//assert"],
                     data = glob(["*_test.go"] # <====== test source files added as test data here!
            )
    your_test.go:40: assertion failed: but assert failed to find the expression to print: a should equal b
FAIL

If the user adds the test source file to their test data in the respective go_test target, they'll now see something like:

--- FAIL: TestAssertShouldWorkUnderBazel (0.00s)
    your_test.go:40: assertion failed: a is not b: a should equal b
FAIL

[CLAassistant]

All committers have signed the CLA.

[cstrahan]

All tests run via go test ./... pass, with the exception of these two (which I believe are due to an issue with the tests when run under macOS, as they were failing before my changes):

--- FAIL: TestChangeWorkingDir (0.00s)
    --- FAIL: TestChangeWorkingDir/changed_to_dir (0.00s)
        env_test.go:138: assertion failed: /private/var/folders/vc/8x3823591cz2_gpk94zpjfv00000gq/T/TestChangeWorkingDir-1487778779 (string) != /var/folders/vc/8x3823591cz2_gpk94zpjfv00000gq/T/TestChangeWorkingDir-1487778779 (string)
--- FAIL: TestChangeWorkingDir_IntegrationWithCleanup (0.00s)
    --- FAIL: TestChangeWorkingDir_IntegrationWithCleanup/cleanup_in_subtest (0.00s)
        env_test.go:157: assertion failed: /private/var/folders/vc/8x3823591cz2_gpk94zpjfv00000gq/T/TestChangeWorkingDir_IntegrationWithCleanup-2603325723 (string) != /var/folders/vc/8x3823591cz2_gpk94zpjfv00000gq/T/TestChangeWorkingDir_IntegrationWithCleanup-2603325723 (string)

I'll see if I can fix the lint issue.

[cstrahan]

Hmm. The ci/circleci: test-golang-1.20 check is failing:

∅  .
✓  assert (689ms)
∅  icmd/internal/stub
∅  internal/assert
∅  internal/cleanup
∅  internal/difflib
∅  internal/maint
∅  x
✓  internal/format (71ms)
✓  assert/opt (72ms)
✓  skip (75ms)
✓  env (75ms)
✓  assert/cmp (75ms)
✓  golden (75ms)
✓  internal/source (76ms)
✓  fs (170ms)
✖  poll (271ms)
✓  icmd (1.411s)
✓  x/subtest (4ms)
✓  assert/cmd/gty-migrate-from-testify (20.483s)

=== Skipped
=== SKIP: env TestPatchAllWindows (0.00s)
    env_test.go:70: runtime.GOOS != "windows"

=== Failed
=== FAIL: poll TestWaitOn_WithCompare (0.09s)
    poll_test.go:86: assertion failed: string "timeout hit after 10ms: first check never completed" does not contain "assertion failed: 3 (int) != 4 (int)"

DONE 289 tests, 1 skipped, 1 failure in 54.413s

Exited with code exit status 1

but that test passes with [email protected] on my machine (running macOS). Maybe a flaky test? Might bump CI with an empty commit.

[cstrahan]

Yay! The tests pass. But I just realized that my editor was hiding the fact that tabs and spaces got mixed together in that big error message string. Just pushed a commit to fix that up.

[dnephin]

Thank you for the PR! I made a couple small changes, but overall this looks great.

Primarily I moved the variables to a bazel.go file, and extracted some of the logic to a new function. This way the variables and the code can be located a bit closer together.

I also extracted the multi-line error message to a raw string to make it a bit easier to read in code. The raw string removes the need to escape the double quotes.

If these changes look alright to you I think this is ready to be merged.

[dnephin]

On this line I added the trailing ) which I believe was missing, and removed the "test source files added as test data here!" comment. Does that seem ok? I guess the glob should capture all the test files.

[cstrahan]

Thanks! Yes, I think this is great 👍

[cstrahan]

@dnephin Those changes look great! Don't see anything else I'd change. Thanks!