cmd/dist: remove deptab and cleanlist in favor of gentab

dist's deptab is a list of changes to the automatically derived set of
package dependencies. It's as old as dist itself, and the first
version of deptab in CL 5620045 was quite complex. From the beginning,
some of the entries in deptab have been for generated files that need
to be added to the dependency set because they can't be discovered if
they don't exist. gentab is also as old as dist itself, and lists the
generated dependency files.

The interaction between deptab and gentab is rather odd. gentab
contains only base file names, not whole paths. To figure out what
files to generate, dist takes a Cartesian product of deptab and gentab
and calls the generator wherever the basename of a path in deptab
matches an entry in gentab. This perhaps made sense at the time
because some of the generated files appeared in more than one package
in deptab.

These days, deptab consists exclusively of generated files because
dist can correctly derive all other dependencies, and all of the
generated files have unique paths. This makes the Cartesian product
approach needlessly complex (and so confusing!), and means that the
only purpose served by deptab is to provide full paths for generated
files.

Furthermore, in the dist clean command, it also needed to expand the
file names in gentab to complete paths, but it did so using a
different list, cleanlist, and the same Cartesian product algorithm.

This CL drops all of this complexity by putting full paths into
gentab, which lets us delete deptab and cleanlist.

Change-Id: Ie3993983734f6da3be453bb4c17a64e22dcf3e8f
Reviewed-on: https://go-review.googlesource.com/c/go/+/501137
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/dist/build.go b/src/cmd/dist/build.go
index 1bf178d0ad54e1b1dc5b064e72783def9f9457c8..d920db9b886f004466b9ae9d803bc396ddabfee9 100644 (file)
--- a/src/cmd/dist/build.go
+++ b/src/cmd/dist/build.go
@@ -614,33 +614,6 @@ func mustLinkExternal(goos, goarch string, cgoEnabled bool) bool {
        return false
 }
 
-// deptab lists changes to the default dependencies for a given prefix.
-// deps ending in /* read the whole directory; deps beginning with -
-// exclude files with that prefix.
-// Note that this table applies only to the build of cmd/go,
-// after the main compiler bootstrap.
-// Files listed here should also be listed in ../distpack/pack.go's srcArch.Remove list.
-var deptab = []struct {
-       prefix string   // prefix of target
-       dep    []string // dependency tweaks for targets with that prefix
-}{
-       {"cmd/go/internal/cfg", []string{
-               "zdefaultcc.go",
-       }},
-       {"go/build", []string{
-               "zcgo.go",
-       }},
-       {"internal/platform", []string{
-               "zosarch.go",
-       }},
-       {"runtime/internal/sys", []string{
-               "zversion.go",
-       }},
-       {"time/tzdata", []string{
-               "zzipdata.go",
-       }},
-}
-
 // depsuffix records the allowed suffixes for source files.
 var depsuffix = []string{
        ".s",
@@ -648,15 +621,17 @@ var depsuffix = []string{
 }
 
 // gentab records how to generate some trivial files.
+// Files listed here should also be listed in ../distpack/pack.go's srcArch.Remove list.
 var gentab = []struct {
-       nameprefix string
-       gen        func(string, string)
+       pkg  string // Relative to $GOROOT/src
+       file string
+       gen  func(dir, file string)
 }{
-       {"zcgo.go", mkzcgo},
-       {"zdefaultcc.go", mkzdefaultcc},
-       {"zosarch.go", mkzosarch},
-       {"zversion.go", mkzversion},
-       {"zzipdata.go", mktzdata},
+       {"go/build", "zcgo.go", mkzcgo},
+       {"cmd/go/internal/cfg", "zdefaultcc.go", mkzdefaultcc},
+       {"internal/platform", "zosarch.go", mkzosarch},
+       {"runtime/internal/sys", "zversion.go", mkzversion},
+       {"time/tzdata", "zzipdata.go", mktzdata},
 }
 
 // installed maps from a dir name (as given to install) to a chan
@@ -680,7 +655,7 @@ func startInstall(dir string) chan struct{} {
        return ch
 }
 
-// runInstall installs the library, package, or binary associated with dir,
+// runInstall installs the library, package, or binary associated with pkg,
 // which is relative to $GOROOT/src.
 func runInstall(pkg string, ch chan struct{}) {
        if pkg == "net" || pkg == "os/user" || pkg == "crypto/x509" {
@@ -767,12 +742,10 @@ func runInstall(pkg string, ch chan struct{}) {
                return !strings.HasPrefix(p, ".") && (!strings.HasPrefix(p, "_") || !strings.HasSuffix(p, ".go"))
        })
 
-       for _, dt := range deptab {
-               if pkg == dt.prefix || strings.HasSuffix(dt.prefix, "/") && strings.HasPrefix(pkg, dt.prefix) {
-                       for _, p := range dt.dep {
-                               p = os.ExpandEnv(p)
-                               files = append(files, p)
-                       }
+       // Add generated files for this package.
+       for _, gt := range gentab {
+               if gt.pkg == pkg {
+                       files = append(files, gt.file)
                }
        }
        files = uniq(files)
@@ -785,7 +758,7 @@ func runInstall(pkg string, ch chan struct{}) {
        }
 
        // Is the target up-to-date?
-       var gofiles, sfiles, missing []string
+       var gofiles, sfiles []string
        stale := rebuildall
        files = filter(files, func(p string) bool {
                for _, suf := range depsuffix {
@@ -807,9 +780,6 @@ func runInstall(pkg string, ch chan struct{}) {
                if t.After(ttarg) {
                        stale = true
                }
-               if t.IsZero() {
-                       missing = append(missing, p)
-               }
                return true
        })
 
@@ -837,32 +807,22 @@ func runInstall(pkg string, ch chan struct{}) {
        }
 
        // Generate any missing files; regenerate existing ones.
-       for _, p := range files {
-               elem := filepath.Base(p)
-               for _, gt := range gentab {
-                       if gt.gen == nil {
-                               continue
-                       }
-                       if strings.HasPrefix(elem, gt.nameprefix) {
-                               if vflag > 1 {
-                                       errprintf("generate %s\n", p)
-                               }
-                               gt.gen(dir, p)
-                               // Do not add generated file to clean list.
-                               // In runtime, we want to be able to
-                               // build the package with the go tool,
-                               // and it assumes these generated files already
-                               // exist (it does not know how to build them).
-                               // The 'clean' command can remove
-                               // the generated files.
-                               goto built
-                       }
+       for _, gt := range gentab {
+               if gt.pkg != pkg {
+                       continue
                }
-               // Did not rebuild p.
-               if find(p, missing) >= 0 {
-                       fatalf("missing file %s", p)
+               p := pathf("%s/%s", dir, gt.file)
+               if vflag > 1 {
+                       errprintf("generate %s\n", p)
                }
-       built:
+               gt.gen(dir, p)
+               // Do not add generated file to clean list.
+               // In runtime, we want to be able to
+               // build the package with the go tool,
+               // and it assumes these generated files already
+               // exist (it does not know how to build them).
+               // The 'clean' command can remove
+               // the generated files.
        }
 
        // Resolve imported packages to actual package paths.
@@ -1186,26 +1146,11 @@ var runtimegen = []string{
        "zversion.go",
 }
 
-// cleanlist is a list of packages with generated files and commands.
-var cleanlist = []string{
-       "runtime/internal/sys",
-       "cmd/cgo",
-       "cmd/go/internal/cfg",
-       "internal/platform",
-       "go/build",
-}
-
 func clean() {
-       for _, name := range cleanlist {
-               path := pathf("%s/src/%s", goroot, name)
-               // Remove generated files.
-               for _, elem := range xreaddir(path) {
-                       for _, gt := range gentab {
-                               if strings.HasPrefix(elem, gt.nameprefix) {
-                                       xremove(pathf("%s/%s", path, elem))
-                               }
-                       }
-               }
+       // Remove generated files.
+       for _, gt := range gentab {
+               path := pathf("%s/src/%s/%s", goroot, gt.pkg, gt.file)
+               xremove(path)
        }
 
        // remove runtimegen files.

diff --git a/src/cmd/distpack/pack.go b/src/cmd/distpack/pack.go
index 55e07f88c331215bfd4684739269ec6f874b6217..cddbd0747dd0256b24a5fd7fb13c6c33adf9ba2d 100644 (file)
--- a/src/cmd/distpack/pack.go
+++ b/src/cmd/distpack/pack.go
@@ -113,7 +113,7 @@ func main() {
                "bin/**",
                "pkg/**",
 
-               // Generated during cmd/dist. See ../dist/build.go:/deptab.
+               // Generated during cmd/dist. See ../dist/build.go:/gentab.
                "src/cmd/go/internal/cfg/zdefaultcc.go",
                "src/go/build/zcgo.go",
                "src/internal/platform/zosarch.go",