cmd/go, go/build: parse directives in file headers

For #56986, go/build needs to report up to cmd/go
about //go:debug lines found in the source code.
Rather than make a special case for //go:debug,
this change gathers all top-level directives above the
package line and includes them in the result.

The go command's module index must match go/build,
so this CL contains the code to update the index as well.

A future CL will use the //go:debug lines to prepare the default
GODEBUG settings, as well as rejecting such lines in non-main
packages.

Change-Id: I66ab8dc72f9cd65c503b10b744367caca233f8a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/453603
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 7c0c104883..11b69cb6f4 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -230,6 +230,9 @@ type PackageInternal struct {
 	TestmainGo        *[]byte              // content for _testmain.go
 	Embed             map[string][]string  // //go:embed comment mapping
 	OrigImportPath    string               // original import path before adding '_test' suffix
+	Directives        []build.Directive
+	TestDirectives    []build.Directive
+	XTestDirectives   []build.Directive
 
 	Asmflags   []string // -asmflags for this package
 	Gcflags    []string // -gcflags for this package
@@ -435,6 +438,9 @@ func (p *Package) copyBuild(opts PackageOpts, pp *build.Package) {
 	p.TestEmbedPatterns = pp.TestEmbedPatterns
 	p.XTestEmbedPatterns = pp.XTestEmbedPatterns
 	p.Internal.OrigImportPath = pp.ImportPath
+	p.Internal.Directives = pp.Directives
+	p.Internal.TestDirectives = pp.TestDirectives
+	p.Internal.XTestDirectives = pp.XTestDirectives
 }
 
 // A PackageError describes an error loading information about a package.