CL 203820 removes an assumption in go/build that srcDir is in the main
module, since in general it need not be. That requires the use of some
other mechanism for callers to communicate the correct location of the
main module.

Fortunately, we already have a WorkingDir field on the ProcessEnv
struct that does exactly that. We can simply propagate it through if
the corresponding field is present on go/build.Context.

Updates golang/go#34860

Change-Id: Idabf9ae06d8383a72772d5a589fae1d10f206c01
Reviewed-on: https://go-review.googlesource.com/c/tools/+/203857
Reviewed-by: Heschi Kreinick <heschi@google.com>

…strings

In CL 203820, we switched go/build to use the caller's working
directory for the main module (rather than srcDir), so that go/build
resolution now respects the requirements and replacements of the main
module. When the passed-in srcDir is empty, as of that CL we use "go
list" instead of falling back to in-process (GOPATH-mode) path lookup.

Unfortunately, that broke go/build.TestImportDirNotExist when
GO111MODULE=on: the test was looking for the specific error message
produced by the in-process lookup.

This change relaxes the test to accept the error message produced by
"go list" when srcDir is empty.

Updates #34769
Updates #34860
Updates #35734
Fixes #36867

Change-Id: Id0f7814a4b7dabe8917216eb013bb4eaee283648
Reviewed-on: https://go-review.googlesource.com/c/go/+/216817
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

Updates #34860
Updates #36168
Updates #36878

Change-Id: I484d7fea5d77d6dcd451d4fdffe0c450eed73636
Reviewed-on: https://go-review.googlesource.com/c/go/+/217124
Reviewed-by: Bryan C. Mills <bcmills@google.com>

This is a followup to CL 199840 and CL 203820. Cumulatively, they caused
a previously known bug to trigger more often while also nearly fixing it.

This change is a small fixup to CL 199840 that resolves the known bug
and prevents it from causing an additional regression in Go 1.14.

Part 1

The intention in CL 199840 was to return the same error that 'go list'
reported when the package wasn't located, so an early return was added.
However, to determine whether the package was located or not, p.Dir was
unintentionally checked instead of dir.

p is initialized to &Package{ImportPath: path} at top of Context.Import,
and its Dir field is never set before that line in importGo is reached.
So return errors.New(errStr) was always executed whenever errStr != "".

Originally, in CL 125296, the "go list" invocation did not include an
'-e' flag, so it would return a non-zero exit code on packages where
build constraints exclude all Go files, and importGo would return an
error like "go/build: importGo import/path: unexpected output: ...".

CL 199840 added an '-e' flag to the "go list" invocation, but checking
the wrong dir variable caused partial package information to never get
populated, and thus issue #31603 continued to occur, although with a
different error message (which ironically included the location of the
package that was supposedly "not found").

Now that the right dir is checked, issue #31603 is fixed.

Part 2

importGo checks whether it can use the go command to find the directory
of a package. In Go 1.13.x and earlier, one of the conditions to use the
go command was that the source directory must be provided.

CL 203820 made a change such that knowing the source directory was
no longer required:

	 // To invoke the go command,
	-// we must know the source directory,
	 // ...

That meant build.Import invocations where srcDir is the empty string:

	build.Import(path, "", build.FindOnly)

Started using the go command to find the directory of the package, and
started to run into issue #31603 as well. That's the #37153 regression.

Since this change fixes issue #31603, it also fixes issue #37153.

Part 3

There is one more thing. Delete the debugImportGo constant, it's unused.

Updates #26504 (CL 125296)
Updates #34752 (CL 199840)
Updates #34860 (CL 203820)
Fixes #31603
Fixes #37153

Change-Id: Iaa7dcc45ba0f708a978950c75fa4c836b87006f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/218817
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

This field was renamed to Dir during the 1.14 development cycle. We
don't need to look for it anymore.

For golang/go#34860

Change-Id: I313a931f070e3dc5a711233e7523c309995fe655
Reviewed-on: https://go-review.googlesource.com/c/tools/+/255397
Run-TryBot: Jay Conrod <jayconrod@google.com>
Trust: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>