immutable/cmd/immutableGen: fix go/packages res and type-based res

We need to fight go/packages a bit to find the right package to use for
type information (see golang/go#27910 for more
details).

Also, our logic for surfacing embedded fields where the embedded type
had a valid go/types.Type was incorrect. It assumed that all such types
must be external to the package being generated, and hence required that
all fields be exported. However, it is possible for a package-local type
to fully type check and therefore be valid. In this case, non-exported
fields _are_ valid for surfacing.

Also a small fix in cmd/gg whereby xtest packages were incorrectly being
considered as not Done() because they were missing a hash (which they
will never have). Added a failsafe that errors in case any work was left
un-Done

immutable/cmd/immutableGen/generator.go

@@ -9,6 +9,9 @@ import (
 	"go/token"
 	"go/types"
 	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
 
 	"golang.org/x/tools/go/packages"
 	"myitcv.io/gogenerate"
@@ -29,18 +32,59 @@ func execute(dir string, envPkg string, licenseHeader string, cmds gogenCmds) {
 	}
 
 	config := &packages.Config{
-		Dir:   absDir,
 		Mode:  packages.LoadSyntax,
 		Fset:  token.NewFileSet(),
-		Tests: false,
+		Tests: true,
 	}
 
 	pkgs, err := packages.Load(config, absDir)
 	if err != nil {
 		fatalf("could not load packages from dir %v: %v", dir, err)
 	}
 
-	pkg := pkgs[0]
+	forTest := regexp.MustCompile(` \[[^\]]+\]$`)
+
+	testPkgs := make(map[string]*packages.Package)
+	var nonTestPkg *packages.Package
+
+	// Becase of https://github.com/golang/go/issues/27910 we have to
+	// apply some janky logic to find the "right" package
+	for _, p := range pkgs {
+		switch {
+		case strings.HasSuffix(p.PkgPath, ".test"):
+			// we don't ever want this package
+			continue
+		case forTest.MatchString(p.ID):
+			testPkgs[p.Name] = p
+		default:
+			nonTestPkg = p
+		}
+	}
+
+	ids := func() []string {
+		var ids []string
+		for _, p := range pkgs {
+			ids = append(ids, p.ID)
+		}
+		sort.Strings(ids)
+		return ids
+	}
+
+	if nonTestPkg == nil {
+		fatalf("always expect to have the actual package. Got %v", ids())
+	}
+
+	var pkg *packages.Package
+
+	if strings.HasSuffix(envPkg, "_test") {
+		if pkg = testPkgs[envPkg]; pkg == nil {
+			fatalf("called with package name %v, but go/packages did not give us such a package. Got %v", envPkg, ids())
+		}
+	} else {
+		if pkg = testPkgs[envPkg]; pkg == nil {
+			pkg = nonTestPkg
+		}
+	}
 
 	if pkg.Name != envPkg {
 		pps := make([]string, 0, len(pkgs))
@@ -135,6 +179,7 @@ type embedded struct {
 	typ  types.Type
 	es   string
 	path []string
+	info *types.Info
 }
 
 type field struct {

immutable/cmd/immutableGen/internal/coretest/core.go

@@ -7,7 +7,7 @@ import (
 	"myitcv.io/immutable/cmd/immutableGen/internal/coretest/pkga"
 )
 
-//go:generate immutableGen -licenseFile license.txt -G "echo \"hello world\""
+//go:generate gobin -m -run myitcv.io/immutable/cmd/immutableGen -licenseFile license.txt -G "echo \"hello world\""
 
 // a comment about MyMap
 type _Imm_MyMap map[string]int
@@ -101,7 +101,8 @@ type _Imm_Embed1 struct {
 }
 
 type _Imm_Embed2 struct {
-	Age int
+	Age          int
+	otherdetails string
 }
 
 type NonImmStruct struct {

immutable/cmd/immutableGen/internal/coretest/core_test.go

@@ -0,0 +1,17 @@
+package coretest_test
+
+import (
+	_ "myitcv.io/immutable/cmd/immutableGen/internal/coretest"
+)
+
+//go:generate gobin -m -run myitcv.io/immutable/cmd/immutableGen -licenseFile license.txt -G "echo \"hello world\""
+
+type _Imm_xtestA struct {
+	*XTestB
+
+	age int
+}
+
+type _Imm_XTestB struct {
+	Name string
+}