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[internal] Infer main field for go_binary #13117

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merged 3 commits into from
Oct 5, 2021

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Eric-Arellano
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Closes #13115.

For now, we allow you to still explicitly set the field, which gives an escape valve if >1 go_package exist for the same directory.

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@Eric-Arellano Eric-Arellano force-pushed the go-binary-main-field branch 2 times, most recently from 20b796e to 5706079 Compare October 5, 2021 14:55
# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]

# Conflicts:
#	testprojects/src/go/pants_test/BUILD
src/python/pants/backend/go/target_types.py Outdated Show resolved Hide resolved
# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
@Eric-Arellano Eric-Arellano enabled auto-merge (squash) October 5, 2021 15:19
@Eric-Arellano Eric-Arellano merged commit 403bfc0 into pantsbuild:main Oct 5, 2021
@Eric-Arellano Eric-Arellano deleted the go-binary-main-field branch October 5, 2021 16:22
Eric-Arellano added a commit that referenced this pull request Oct 6, 2021
Closes #13049. This greatly reduces boilerplate and also allows us to make some fields required like `import_path` and `subpath`, so that we don't have to calculate those in consuming rules like `build_go_pkg.py`.

## The address format

The generated address looks like `project#./dir`. @tdyas offered that this is intuitive for Go developers because they have to say `go build ./dir` already with the leading `./`. 

This solves how to represent when the `_go_internal_package` is in the same dir as the `go_mod`: `project#./`.

This also makes very clear the difference from external packages like `project#rsc.io/quote` vs. internal packages like `project#./dir`.

## Improves dependency inference

Now that the `import_path` field is required for both `_go_internal_package` and `_go_external_package`, we can create a global mapping of `import_path -> pkg_target`. This is necessary for #13114.

This also improves performance. We don't need to call `ResolvedGoPackage` on all the candidate targets a package might depend on to calculate their import paths. We do still need it when resolving the deps of a particular `_go_internal_package`, but we can be lazier when we call that codepath in not evaluating all candidate targets.

### `dependencies` benchmark

As expected, there is no difference because we are finding the dependencies of everything, so we still have to call `ResolvedGoPackage`. The perf gains are only in things sometimes being less eager, which isn't the case here.

Before:

```
❯ hyperfine -r 5 './pants_from_sources --no-pantsd --no-process-execution-local-cache dependencies ::'
  Time (mean ± σ):     26.501 s ±  1.537 s    [User: 29.554 s, System: 24.115 s]
  Range (min … max):   24.928 s … 28.763 s    5 runs
```

After:
```
❯ hyperfine -r 5 './pants_from_sources --no-pantsd --no-process-execution-local-cache dependencies ::'
  Time (mean ± σ):     26.359 s ±  0.526 s    [User: 29.600 s, System: 23.769 s]
  Range (min … max):   25.625 s … 26.993 s    5 runs
```

### `package` benchmark

Before:

```
❯ hyperfine -r 5 './pants_from_sources --no-pantsd --no-process-execution-local-cache package ::'
  Time (mean ± σ):     33.777 s ±  0.248 s    [User: 39.221 s, System: 39.389 s]
  Range (min … max):   33.517 s … 34.062 s    5 runs
```

After:

```
❯ hyperfine -r 5 './pants_from_sources --no-pantsd --no-process-execution-local-cache package ::'
Benchmark #1: ./pants_from_sources --no-pantsd --no-process-execution-local-cache package ::
  Time (mean ± σ):     31.049 s ±  0.702 s    [User: 40.606 s, System: 40.537 s]
  Range (min … max):   30.512 s … 32.273 s    5 runs
```

## TODO: fix `go_binary` inference of `main` field

#13117 added inference of the `main` field for `go_binary`, that it defaults to the `go_package` defined in that directory.

But target generation no longer generates targets actually in each directory. All generated targets are "located" in the BUILD file of the `go_mod`, i.e. their `spec_path` is set to that. So it no longer looks to `AddressSpecs` like there are any targets in each subdirectory, and there are >1 `_go_internal_package` targets in the `go_mod` dir.

Instead, we should use the `subpath` field to determine what directory the targets correspond to.

[ci skip-rust]
[ci skip-build-wheels]
Eric-Arellano added a commit that referenced this pull request Oct 8, 2021
…rated targets (#13163)

Restores support for #13117 post-#13139.

[ci skip-rust]
@stuhood stuhood mentioned this pull request Oct 11, 2021
stuhood added a commit to stuhood/pants that referenced this pull request Apr 6, 2022
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Go: should go_binary automatically determine the go_package?
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