cmd/go, go/build: add ToolTags to build.Default

The build.Default context really needs to accurately describe
the default build context. The goexperiment tags being a special
case in the go command violates that rule and is the root cause
of the various try-bot failures blocking the enabling of regabi.

(The cleanups I made in golang.org/x/tools were long overdue
but are not strictly necessary for making regabi work; this CL is.)

Having moved the GOEXPERIMENT parsing into internal/buildcfg,
go/build can now use it to set up build.Default, in the new field
ToolTags, meant to hold toolchain-determined tags (for now,
just the experiments). And at the same time we can remove the
duplication of GOOS and GOARCH defaults.

And then once build.Default is set up accurately, the special case
code in cmd/go itself can be removed, and the special case code
in test/run.go is at least a bit less special.

Change-Id: Ib7394e10aa018e492cb9a83fb8fb9a5011a8c25b
Reviewed-on: https://go-review.googlesource.com/c/go/+/310732
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 999fcf7e531f2605bbef4fc6ee73eae148e59adf..9d4626769d64adb025f48a473c9c6a9ad4d938b4 100644 (file)
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -841,6 +841,7 @@
 //         UseAllFiles   bool     // use files regardless of +build lines, file names
 //         Compiler      string   // compiler to assume when computing target paths
 //         BuildTags     []string // build constraints to match in +build lines
+//         ToolTags      []string // toolchain-specific build constraints
 //         ReleaseTags   []string // releases the current release is compatible with
 //         InstallSuffix string   // suffix to use in the name of the install dir
 //     }

diff --git a/src/cmd/go/internal/list/context.go b/src/cmd/go/internal/list/context.go
index 68d691ebe2eeccd0e7f16ca8528204d0296854e9..2dc63766b70654576156bebd007d6b35c0def832 100644 (file)
--- a/src/cmd/go/internal/list/context.go
+++ b/src/cmd/go/internal/list/context.go
@@ -17,6 +17,7 @@ type Context struct {
        UseAllFiles   bool     `json:",omitempty"` // use files regardless of +build lines, file names
        Compiler      string   `json:",omitempty"` // compiler to assume when computing target paths
        BuildTags     []string `json:",omitempty"` // build constraints to match in +build lines
+       ToolTags      []string `json:",omitempty"` // toolchain-specific build constraints
        ReleaseTags   []string `json:",omitempty"` // releases the current release is compatible with
        InstallSuffix string   `json:",omitempty"` // suffix to use in the name of the install dir
 }
@@ -31,6 +32,7 @@ func newContext(c *build.Context) *Context {
                UseAllFiles:   c.UseAllFiles,
                Compiler:      c.Compiler,
                BuildTags:     c.BuildTags,
+               ToolTags:      c.ToolTags,
                ReleaseTags:   c.ReleaseTags,
                InstallSuffix: c.InstallSuffix,
        }

diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index 221370bd19706b81667169c31a94741c833305fa..53bf75e27e0d351f8e05937103fe3ce9e7c0790e 100644 (file)
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -148,6 +148,7 @@ The template function "context" returns the build context, defined as:
         UseAllFiles   bool     // use files regardless of +build lines, file names
         Compiler      string   // compiler to assume when computing target paths
         BuildTags     []string // build constraints to match in +build lines
+        ToolTags      []string // toolchain-specific build constraints
         ReleaseTags   []string // releases the current release is compatible with
         InstallSuffix string   // suffix to use in the name of the install dir
     }

diff --git a/src/cmd/go/internal/work/init.go b/src/cmd/go/internal/work/init.go
index 66e1ca7d80ba52bca5053d855fc967d29f872a2c..ca7e04d280bfaecb5461aa838456ed675f9a4d10 100644 (file)
--- a/src/cmd/go/internal/work/init.go
+++ b/src/cmd/go/internal/work/init.go
@@ -14,7 +14,6 @@ import (
        "cmd/internal/sys"
        "flag"
        "fmt"
-       "internal/buildcfg"
        "os"
        "path/filepath"
        "runtime"
@@ -46,15 +45,6 @@ func BuildInit() {
                        base.Fatalf("go %s: %s environment variable is relative; must be absolute path: %s\n", flag.Args()[0], key, path)
                }
        }
-
-       // For each experiment that has been enabled in the toolchain, define a
-       // build tag with the same name but prefixed by "goexperiment." which can be
-       // used for compiling alternative files for the experiment. This allows
-       // changes for the experiment, like extra struct fields in the runtime,
-       // without affecting the base non-experiment code at all.
-       for _, expt := range buildcfg.EnabledExperiments() {
-               cfg.BuildContext.BuildTags = append(cfg.BuildContext.BuildTags, "goexperiment."+expt)
-       }
 }
 
 func instrumentInit() {

diff --git a/src/go/build/build.go b/src/go/build/build.go
index 501ce2e8dd2703fecdc0acc974cca47a7cd3c10b..8d1a107c6ea713836407ae143607cf2f8a858348 100644 (file)
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -12,6 +12,7 @@ import (
        "go/build/constraint"
        "go/doc"
        "go/token"
+       "internal/buildcfg"
        exec "internal/execabs"
        "internal/goroot"
        "internal/goversion"
@@ -48,16 +49,18 @@ type Context struct {
        UseAllFiles bool   // use files regardless of +build lines, file names
        Compiler    string // compiler to assume when computing target paths
 
-       // The build and release tags specify build constraints
+       // The build, tool, and release tags specify build constraints
        // that should be considered satisfied when processing +build lines.
        // Clients creating a new context may customize BuildTags, which
-       // defaults to empty, but it is usually an error to customize ReleaseTags,
-       // which defaults to the list of Go releases the current release is compatible with.
+       // defaults to empty, but it is usually an error to customize ToolTags or ReleaseTags.
+       // ToolTags defaults to build tags appropriate to the current Go toolchain configuration.
+       // ReleaseTags defaults to the list of Go releases the current release is compatible with.
        // BuildTags is not set for the Default build Context.
-       // In addition to the BuildTags and ReleaseTags, build constraints
+       // In addition to the BuildTags, ToolTags, and ReleaseTags, build constraints
        // consider the values of GOARCH and GOOS as satisfied tags.
        // The last element in ReleaseTags is assumed to be the current release.
        BuildTags   []string
+       ToolTags    []string
        ReleaseTags []string
 
        // The install suffix specifies a suffix to use in the name of the installation
@@ -292,17 +295,27 @@ func defaultGOPATH() string {
        return ""
 }
 
-var defaultReleaseTags []string
+var defaultToolTags, defaultReleaseTags []string
 
 func defaultContext() Context {
        var c Context
 
-       c.GOARCH = envOr("GOARCH", runtime.GOARCH)
-       c.GOOS = envOr("GOOS", runtime.GOOS)
+       c.GOARCH = buildcfg.GOARCH
+       c.GOOS = buildcfg.GOOS
        c.GOROOT = pathpkg.Clean(runtime.GOROOT())
        c.GOPATH = envOr("GOPATH", defaultGOPATH())
        c.Compiler = runtime.Compiler
 
+       // For each experiment that has been enabled in the toolchain, define a
+       // build tag with the same name but prefixed by "goexperiment." which can be
+       // used for compiling alternative files for the experiment. This allows
+       // changes for the experiment, like extra struct fields in the runtime,
+       // without affecting the base non-experiment code at all.
+       for _, exp := range buildcfg.EnabledExperiments() {
+               c.ToolTags = append(c.ToolTags, "goexperiment."+exp)
+       }
+       defaultToolTags = append([]string{}, c.ToolTags...) // our own private copy
+
        // Each major Go release in the Go 1.x series adds a new
        // "go1.x" release tag. That is, the go1.x tag is present in
        // all releases >= Go 1.x. Code that requires Go 1.x or later
@@ -1056,7 +1069,7 @@ func (ctxt *Context) importGo(p *Package, path, srcDir string, mode ImportMode)
        // we must not being doing special things like AllowBinary or IgnoreVendor,
        // and all the file system callbacks must be nil (we're meant to use the local file system).
        if mode&AllowBinary != 0 || mode&IgnoreVendor != 0 ||
-               ctxt.JoinPath != nil || ctxt.SplitPathList != nil || ctxt.IsAbsPath != nil || ctxt.IsDir != nil || ctxt.HasSubdir != nil || ctxt.ReadDir != nil || ctxt.OpenFile != nil || !equal(ctxt.ReleaseTags, defaultReleaseTags) {
+               ctxt.JoinPath != nil || ctxt.SplitPathList != nil || ctxt.IsAbsPath != nil || ctxt.IsDir != nil || ctxt.HasSubdir != nil || ctxt.ReadDir != nil || ctxt.OpenFile != nil || !equal(ctxt.ToolTags, defaultToolTags) || !equal(ctxt.ReleaseTags, defaultReleaseTags) {
                return errNoModules
        }
 
@@ -1892,6 +1905,11 @@ func (ctxt *Context) matchTag(name string, allTags map[string]bool) bool {
                        return true
                }
        }
+       for _, tag := range ctxt.ToolTags {
+               if tag == name {
+                       return true
+               }
+       }
        for _, tag := range ctxt.ReleaseTags {
                if tag == name {
                        return true

diff --git a/test/run.go b/test/run.go
index feec2b50beb2eb1349f284376bb461315fb9752a..5e60de762482b2d33ab3f483492cc57c137c410d 100644 (file)
--- a/test/run.go
+++ b/test/run.go
@@ -12,6 +12,7 @@ import (
        "errors"
        "flag"
        "fmt"
+       "go/build"
        "hash/fnv"
        "io"
        "io/fs"
@@ -376,7 +377,6 @@ type context struct {
        GOARCH     string
        cgoEnabled bool
        noOptEnv   bool
-       expTags    map[string]bool // Set lazily
 }
 
 // shouldTest looks for build tags in a source file and returns
@@ -447,27 +447,12 @@ func (ctxt *context) match(name string) bool {
        }
 
        if strings.HasPrefix(name, "goexperiment.") {
-               // Query goexperiment tags from the toolchain.
-               if ctxt.expTags == nil {
-                       ctxt.expTags = make(map[string]bool)
-                       cmd := exec.Command(goTool(), "tool", "compile", "-V=goexperiment")
-                       out, err := cmd.CombinedOutput()
-                       if err != nil {
-                               log.Fatalf("failed to get GOEXPERIMENT configuration:\n%s", out)
-                       }
-                       i := bytes.Index(out, []byte("X:"))
-                       if i != -1 {
-                               for _, exp := range strings.Split(string(out[i+2:]), ",") {
-                                       v := true
-                                       if strings.HasPrefix(exp, "no") {
-                                               v, exp = false, exp[2:]
-                                       }
-                                       ctxt.expTags["goexperiment."+exp] = v
-                               }
+               for _, tag := range build.Default.ToolTags {
+                       if tag == name {
+                               return true
                        }
                }
-
-               return ctxt.expTags[name]
+               return false
        }
 
        if name == "cgo" && ctxt.cgoEnabled {