cmd/go: eliminate redundancy in import error messages

This change introduces a new interface, load.ImportPathError. An error
may satisfy this by providing an ImportPath method and including the
import path in its error text. modload.ImportMissingError satisfies
this interface. load.ImportErrorf also provides a convenient way to
create an error satisfying this interface with an arbitrary message.

When load.PackageError formats its error text, it may omit the last
path on the import stack if the wrapped error satisfies
ImportPathError and has a matching path.

To make this work, PackageError.Err is now an error instead of a
string. PackageError.MarshalJSON will write Err as a string for
'go list -json' output.

When go/build.Import invokes 'go list' in module mode, it now runs
with '-e' and includes '.Error' in the output format instead of
expecting the error to be in the raw stderr text. If a package error
is printed and a directory was not found, the error will be returned
without extra decoration.

Fixes #34752

Change-Id: I2d81dab7dec19e0ae9f51f6412bc9f30433a8596
Reviewed-on: https://go-review.googlesource.com/c/go/+/199840
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
9 files changed
tree: 0729564f213df6c7ee643d71da5f9c66dd2cccb2
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. AUTHORS
  11. CONTRIBUTING.md
  12. CONTRIBUTORS
  13. favicon.ico
  14. LICENSE
  15. PATENTS
  16. README.md
  17. robots.txt
  18. 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 3.0 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://golang.org/dl/.

After downloading a binary release, visit https://golang.org/doc/install or load doc/install.html in your web browser for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit https://golang.org/doc/install/source or load doc/install-source.html in your web browser for source installation instructions.

Contributing

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

To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html

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