PythonInspector: Fix a deserialization issue

If a project defines no dependencies python-inspector returns an empty
object instead of an empty array [1]. Create a custom deserializer as a
workaround to not fail during deserialization.

[1]: aboutcode-org/python-inspector#94

Signed-off-by: Martin Nonnenmacher <[email protected]>

Author: mnonnenmacher

analyzer/src/funTest/kotlin/managers/PipFunTest.kt

@@ -20,6 +20,8 @@
 package org.ossreviewtoolkit.analyzer.managers
 
 import io.kotest.core.spec.style.WordSpec
+import io.kotest.matchers.collections.beEmpty
+import io.kotest.matchers.should
 import io.kotest.matchers.shouldBe
 
 import java.io.File
@@ -31,6 +33,7 @@ import org.ossreviewtoolkit.model.config.RepositoryConfiguration
 import org.ossreviewtoolkit.utils.common.Os
 import org.ossreviewtoolkit.utils.ort.normalizeVcsUrl
 import org.ossreviewtoolkit.utils.test.USER_DIR
+import org.ossreviewtoolkit.utils.test.createTestTempFile
 import org.ossreviewtoolkit.utils.test.patchExpectedResult
 
 class PipFunTest : WordSpec({
@@ -114,6 +117,14 @@ class PipFunTest : WordSpec({
 
             result.toYaml() shouldBe expectedResult
         }
+
+        "not fail if the requirements file is empty" {
+            val definitionFile = createTestTempFile(prefix = "requirements", suffix = ".txt")
+
+            val result = createPip().resolveSingleProject(definitionFile)
+
+            result.issues should beEmpty()
+        }
     }
 })
 

analyzer/src/main/kotlin/managers/utils/PythonInspector.kt

@@ -26,7 +26,11 @@ import java.util.SortedSet
 
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.builtins.ListSerializer
 import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonArray
+import kotlinx.serialization.json.JsonElement
+import kotlinx.serialization.json.JsonTransformingSerializer
 import kotlinx.serialization.json.decodeFromStream
 
 import org.apache.logging.log4j.kotlin.Logging
@@ -112,10 +116,18 @@ internal object PythonInspector : CommandLineTool, Logging {
     @Serializable
     internal data class Result(
         @SerialName("files") val projects: List<Project>,
-        @SerialName("resolved_dependencies_graph") val resolvedDependenciesGraph: List<ResolvedDependency>,
+        @SerialName("resolved_dependencies_graph")
+        @Serializable(with = DependencyGraphDeserializer::class)
+        val resolvedDependenciesGraph: List<ResolvedDependency>,
         val packages: List<Package>
     )
 
+    object DependencyGraphDeserializer :
+        JsonTransformingSerializer<List<ResolvedDependency>>(ListSerializer(ResolvedDependency.serializer())) {
+        override fun transformDeserialize(element: JsonElement): JsonElement =
+            if (element !is JsonArray) JsonArray(emptyList()) else element
+    }
+
     @Serializable
     internal data class Project(
         val path: String,