migrate json schema generation (#4270)

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

internal/packagemetadata/generate/main.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/anchore/syft/internal/packagemetadata"
+	"github.com/dave/jennifer/jen"
+)
+
+// This program is invoked from syft/internal and generates packagemetadata/generated.go
+
+const (
+	pkgImport = "github.com/anchore/syft/syft/pkg"
+	path      = "packagemetadata/generated.go"
+)
+
+func main() {
+	typeNames, err := packagemetadata.DiscoverTypeNames()
+	if err != nil {
+		panic(fmt.Errorf("unable to get all metadata type names: %w", err))
+	}
+
+	// useful for debugging...
+	// for _, typeName := range typeNames {
+	//	fmt.Printf(" - %s\n", typeName)
+	//}
+
+	fmt.Printf("updating package metadata type list with %+v types\n", len(typeNames))
+
+	f := jen.NewFile("packagemetadata")
+	f.HeaderComment("DO NOT EDIT: generated by internal/packagemetadata/generate/main.go")
+	f.ImportName(pkgImport, "pkg")
+	f.Comment("AllTypes returns a list of all pkg metadata types that syft supports (that are represented in the pkg.Package.Metadata field).")
+
+	f.Func().Id("AllTypes").Params().Index().Any().BlockFunc(func(g *jen.Group) {
+		g.ReturnFunc(func(g *jen.Group) {
+			g.Index().Any().ValuesFunc(func(g *jen.Group) {
+				for _, typeName := range typeNames {
+					g.Qual(pkgImport, typeName).Values()
+				}
+			})
+		})
+	})
+
+	rendered := fmt.Sprintf("%#v", f)
+
+	fh, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		panic(fmt.Errorf("unable to open file: %w", err))
+	}
+
+	// fix a little whitespacing
+	rendered = strings.ReplaceAll(rendered, ",", ",\n")
+	rendered = strings.ReplaceAll(rendered, "[]any{", "[]any{\n")
+	rendered = strings.ReplaceAll(rendered, "}}\n}", "},\n}\n}")
+
+	_, err = fh.WriteString(rendered)
+	if err != nil {
+		panic(fmt.Errorf("unable to write file: %w", err))
+	}
+	if err := fh.Close(); err != nil {
+		panic(fmt.Errorf("unable to close file: %w", err))
+	}
+}