Extract language and package type from pURLs on SBOM decode (#777)

* add language detection from pURLs

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* add package type detection from pURLs

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* add cargo and npm pURL support

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* fix npm tests and linting

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

syft/pkg/language.go

@@ -1,5 +1,7 @@
 package pkg
 
+import "github.com/anchore/packageurl-go"
+
 // Language represents a single programming language.
 type Language string
 
@@ -30,3 +32,29 @@ var AllLanguages = []Language{
 func (l Language) String() string {
 	return string(l)
 }
+
+func LanguageFromPURL(p string) Language {
+	purl, err := packageurl.FromString(p)
+	if err != nil {
+		return UnknownLanguage
+	}
+
+	switch purl.Type {
+	case packageurl.TypeMaven, purlGradlePkgType:
+		return Java
+	case packageurl.TypeComposer:
+		return PHP
+	case packageurl.TypeGolang:
+		return Go
+	case packageurl.TypeNPM:
+		return JavaScript
+	case packageurl.TypePyPi:
+		return Python
+	case packageurl.TypeGem:
+		return Ruby
+	case purlCargoPkgType:
+		return Rust
+	default:
+		return UnknownLanguage
+	}
+}