internal/testenv: avoid rebuilding all of std in WriteImportcfg

Instead, have the caller pass in an explicit list of the packages
(if any) they need.

After #47257, a builder running a test does not necessarily have the
entire standard library already cached, especially when running tests
in sharded mode. testenv.WriteImportcfg used to write an importcfg for
the entire standard library — which required rebuilding the entire
standard library — even though most tests need only a tiny subset.

This reduces the time to test internal/abi with a cold build cache on
my workstation from ~16s to ~0.05s.

It somewhat increases the time for 'go test go/internal/gcimporter'
with a cold cache, from ~43s to ~54s, presumably due to decreased
parallelism in rebuilding the standard library and increased overhead
in re-resolving the import map. However, 'go test -short' running time
remains stable (~5.5s before and after).

Fixes #58248.

Change-Id: I9be6b61ae6e28b75b53af85207c281bb93b9346f
Reviewed-on: https://go-review.googlesource.com/c/go/+/464736
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
8 files changed
tree: cc68055be7392a361312de837006dc8cbeb56c54
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. codereview.cfg
  11. CONTRIBUTING.md
  12. go.env
  13. LICENSE
  14. PATENTS
  15. README.md
  16. SECURITY.md
README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image Gopher image by Renee French, licensed under Creative Commons 4.0 Attributions license.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

Download and Install

Binary Distributions

Official binary distributions are available at https://go.dev/dl/.

After downloading a binary release, visit https://go.dev/doc/install for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit https://go.dev/doc/install/source for source installation instructions.

Contributing

Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines at https://go.dev/doc/contribute.

Note that the Go project uses the issue tracker for bug reports and proposals only. See https://go.dev/wiki/Questions for a list of places to ask questions about the Go language.