feat(analyzer): Log about configured but unavailable package managers

This somewhat restores a feature when package managers were enabled /
disabled via dedicated command line options instead of configuration. In
case an unavailable package manager is disabled, only warn, as not using
the package manager is the desired effect in that case anyway.

Signed-off-by: Sebastian Schuberth <[email protected]>

Author: sschuberth

analyzer/src/main/kotlin/Extensions.kt

@@ -19,16 +19,33 @@
 
 package org.ossreviewtoolkit.analyzer
 
+import org.apache.logging.log4j.kotlin.logger
+
 import org.ossreviewtoolkit.model.config.AnalyzerConfiguration
+import org.ossreviewtoolkit.utils.common.alsoIfNull
 
 /**
  * Return the list of enabled [PackageManager]s based on the [AnalyzerConfiguration.enabledPackageManagers] and
  * [AnalyzerConfiguration.disabledPackageManagers] configuration properties and the
  * [default][PackageManagerFactory.isEnabledByDefault] of the [PackageManager]s.
  */
 fun AnalyzerConfiguration.determineEnabledPackageManagers(): Set<PackageManagerFactory> {
-    val enabled = enabledPackageManagers?.mapNotNull { PackageManager.ALL[it] } ?: PackageManager.ENABLED_BY_DEFAULT
-    val disabled = disabledPackageManagers?.mapNotNull { PackageManager.ALL[it] }.orEmpty()
+    val enabled = enabledPackageManagers?.mapNotNull { name ->
+        PackageManager.ALL[name].alsoIfNull {
+            logger.error {
+                "Package manager '$name' is configured to be enabled but is not available in the classpath. It must " +
+                    "be one of: ${PackageManager.ALL.keys.joinToString()}."
+            }
+        }
+    } ?: PackageManager.ENABLED_BY_DEFAULT
+
+    val disabled = disabledPackageManagers?.mapNotNull { name ->
+        PackageManager.ALL[name].alsoIfNull {
+            logger.warn {
+                "Package manager '$name' is configured to be disabled but is not available in the classpath."
+            }
+        }
+    }.orEmpty()
 
     return enabled.toSet() - disabled.toSet()
 }