chore: only extract versions from packages in the generator ecosystem (#957)

Cherry-picked from G-Rath/osv-detector#241

---

Currently the generators assume that all packages in an OSV are for
their respective ecosystem which since they download ecosystem-specific
databases is _mostly_ true, but there are a few OSVs that are for
packages that exist across more than one ecosystem.

This has not been a problem up until now because either the versions in
such OSVs happen to be compatible with native ecosystem version parser
or we're skipping invalid versions for legacy reasons, but now
GHSA-5844-q3fc-56rh exists which has versions that are invalid in Ruby.

Author: G-Rath

scripts/generators/GenerateMavenVersions.java

@@ -94,6 +94,10 @@ public static Map<String, List<String>> fetchPackageVersions() throws IOExceptio
     osvs.forEach(osv -> osv.getJSONArray("affected").forEach(aff -> {
       JSONObject affected = (JSONObject) aff;
 
+      if(affected.getJSONObject("package").getString("ecosystem").equals("Maven")) {
+        return;
+      }
+
       String pkgName = affected.getJSONObject("package").getString("name");
 
       if(!affected.has("versions")) {

scripts/generators/generate-cran-versions.R

@@ -24,6 +24,10 @@ extract_packages_with_versions <- function(osvs) {
 
   for (osv in osvs) {
     for (affected in osv$affected) {
+      if (affected$package$ecosystem != "CRAN") {
+        next
+      }
+
       package <- affected$package$name
 
       if (!(package %in% names(result))) {

scripts/generators/generate-debian-versions.py

@@ -47,6 +47,9 @@ def extract_packages_with_versions(osvs):
 
   for osv in osvs:
     for affected in osv['affected']:
+      if not affected['package']['ecosystem'].startswith('Debian'):
+        continue
+
       package = affected['package']['name']
 
       if package not in dict:

scripts/generators/generate-packagist-versions.php

@@ -79,6 +79,10 @@ function fetchPackageVersions(): array
 
   foreach ($osvs as $osv) {
     foreach ($osv['affected'] as $affected) {
+      if ($affected['package']['ecosystem'] !== 'Packagist') {
+        continue;
+      }
+
       $package = $affected['package']['name'];
 
       if (!isset($packages[$package])) {

scripts/generators/generate-pypi-versions.py

@@ -40,6 +40,9 @@ def extract_packages_with_versions(osvs):
 
   for osv in osvs:
     for affected in osv['affected']:
+      if affected['package']['ecosystem'] != 'PyPI':
+        continue
+
       package = affected['package']['name']
 
       if package not in dict: