fix(godocfx): filter out other modules, sort pkgs (#2894)

The sort keeps the TOC in a stable order.

internal/godocfx/go.sum

@@ -67,6 +67,7 @@ github.com/google/go-cmp v0.5.2 h1:X2ev0eStA3AbceY54o37/0PQ/UWqKEiiO2dKL5OPaFM=
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/martian/v3 v3.0.0 h1:pMen7vLs8nvgEYhywH3KDWJIJTeEr2ULsVWHWYHQyBs=
 github.com/google/martian/v3 v3.0.0/go.mod h1:y5Zk1BBys9G+gd6Jrk0W3cC1+ELVxBWuIGO+w/tUAp0=
+github.com/google/pprof v0.0.0-20200905233945-acf8798be1f7 h1:k+KkMRk8mGOu1xG38StS7dQ+Z6oW1i9n3dgrAVU9Q/E=
 github.com/google/pprof v0.0.0-20200905233945-acf8798be1f7/go.mod h1:ZgVRPoUq/hfqzAqh7sHMqb3I9Rq5C59dIz2SbBwJ4eM=
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
 github.com/googleapis/gax-go/v2 v2.0.5 h1:sjZBwGj9Jlw33ImPtvFviGYvseOtDM7hkSKB7+Tv3SM=

internal/godocfx/parse.go

@@ -122,7 +122,7 @@ func parse(glob string) (map[string]*page, tableOfContents, *packages.Module, er
 
 	// First, collect all of the files grouped by package, including test
 	// packages.
-	pkgFiles := map[string][]string{}
+	allPkgFiles := map[string][]string{}
 	for _, pkg := range pkgs {
 		id := pkg.ID
 		// See https://pkg.go.dev/golang.org/x/tools/go/packages#Config.
@@ -144,17 +144,35 @@ func parse(glob string) (map[string]*page, tableOfContents, *packages.Module, er
 		for _, f := range pkg.Syntax {
 			name := pkg.Fset.File(f.Pos()).Name()
 			if strings.HasSuffix(name, ".go") {
-				pkgFiles[id] = append(pkgFiles[id], name)
+				allPkgFiles[id] = append(allPkgFiles[id], name)
+			}
+		}
+	}
+
+	// Test files don't have Module set. Filter out packages in skipped modules.
+	pkgFiles := map[string][]string{}
+	pkgNames := []string{}
+	for pkgPath, files := range allPkgFiles {
+		skip := false
+		for skipped := range skippedModules {
+			if strings.HasPrefix(pkgPath, skipped) {
+				skip = true
+				break
 			}
 		}
+		if !skip {
+			pkgFiles[pkgPath] = files
+			pkgNames = append(pkgNames, pkgPath)
+		}
 	}
+	sort.Strings(pkgNames)
 
 	// Once the files are grouped by package, process each package
 	// independently.
-	for pkgPath, files := range pkgFiles {
+	for _, pkgPath := range pkgNames {
 		parsedFiles := []*ast.File{}
 		fset := token.NewFileSet()
-		for _, f := range files {
+		for _, f := range pkgFiles[pkgPath] {
 			pf, err := parser.ParseFile(fset, f, nil, parser.ParseComments)
 			if err != nil {
 				return nil, nil, nil, fmt.Errorf("ParseFile: %v", err)
@@ -168,6 +186,11 @@ func parse(glob string) (map[string]*page, tableOfContents, *packages.Module, er
 			return nil, nil, nil, fmt.Errorf("doc.NewFromFiles: %v", err)
 		}
 
+		// Extra filter in case the file filtering didn't catch everything.
+		if !strings.HasPrefix(docPkg.ImportPath, module.Path) {
+			continue
+		}
+
 		toc = append(toc, &tocItem{
 			UID:  docPkg.ImportPath,
 			Name: docPkg.ImportPath,