Support python type hints (#1701)

---------

Co-authored-by: Maximilian Kaul <[email protected]>

cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/PythonLanguageFrontend.kt

@@ -144,24 +144,7 @@ class PythonLanguageFrontend(language: Language<PythonLanguageFrontend>, ctx: Tr
                 autoType()
             }
             is Python.AST.Name -> {
-                // We have some kind of name here; let's quickly check, if this is a primitive type
-                val id = type.id
-                if (id in language.primitiveTypeNames) {
-                    return primitiveType(id)
-                }
-
-                // Otherwise, this could already be a fully qualified type
-                val name =
-                    if (language.namespaceDelimiter in id) {
-                        // TODO: This might create problem with nested classes
-                        parseName(id)
-                    } else {
-                        // otherwise, we can just simply take the unqualified name and the type
-                        // resolver will take care of the rest
-                        id
-                    }
-
-                objectType(name)
+                this.typeOf(type.id)
             }
             else -> {
                 // The AST supplied us with some kind of type information, but we could not parse
@@ -171,6 +154,21 @@ class PythonLanguageFrontend(language: Language<PythonLanguageFrontend>, ctx: Tr
         }
     }
 
+    /** Resolves a [Type] based on its string identifier. */
+    fun typeOf(typeId: String): Type {
+        // Check if the typeId contains a namespace delimiter for qualified types
+        val name =
+            if (language.namespaceDelimiter in typeId) {
+                // TODO: This might create problem with nested classes
+                parseName(typeId)
+            } else {
+                // Unqualified name, resolved by the type resolver
+                typeId
+            }
+
+        return objectType(name)
+    }
+
     /**
      * This functions extracts the source code from the input file given a location. This is a bit
      * tricky in Python, as indents are part of the syntax. We also don't want to include leading

cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/StatementHandler.kt

@@ -36,6 +36,7 @@ import de.fraunhofer.aisec.cpg.graph.declarations.*
 import de.fraunhofer.aisec.cpg.graph.statements.AssertStatement
 import de.fraunhofer.aisec.cpg.graph.statements.DeclarationStatement
 import de.fraunhofer.aisec.cpg.graph.statements.Statement
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.AssignExpression
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.Block
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.Expression
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.MemberExpression
@@ -196,18 +197,15 @@ class StatementHandler(frontend: PythonLanguageFrontend) :
         return frontend.expressionHandler.handle(node.value)
     }
 
-    private fun handleAnnAssign(node: Python.AST.AnnAssign): Statement {
-        // TODO: annotations
+    /**
+     * Translates a Python [`AnnAssign`](https://docs.python.org/3/library/ast.html#ast.AnnAssign)
+     * into an [AssignExpression].
+     */
+    private fun handleAnnAssign(node: Python.AST.AnnAssign): AssignExpression {
         val lhs = frontend.expressionHandler.handle(node.target)
-        return if (node.value != null) {
-            newAssignExpression(
-                lhs = listOf(lhs),
-                rhs = listOf(frontend.expressionHandler.handle(node.value!!)), // TODO !!
-                rawNode = node
-            )
-        } else {
-            lhs
-        }
+        lhs.type = frontend.typeOf(node.annotation)
+        val rhs = node.value?.let { listOf(frontend.expressionHandler.handle(it)) } ?: emptyList()
+        return newAssignExpression(lhs = listOf(lhs), rhs = rhs, rawNode = node)
     }
 
     private fun handleIf(node: Python.AST.If): Statement {
@@ -234,8 +232,16 @@ class StatementHandler(frontend: PythonLanguageFrontend) :
         return ret
     }
 
-    private fun handleAssign(node: Python.AST.Assign): Statement {
+    /**
+     * Translates a Python [`Assign`](https://docs.python.org/3/library/ast.html#ast.Assign) into an
+     * [AssignExpression].
+     */
+    private fun handleAssign(node: Python.AST.Assign): AssignExpression {
         val lhs = node.targets.map { frontend.expressionHandler.handle(it) }
+        node.type_comment?.let { typeComment ->
+            val tpe = frontend.typeOf(typeComment)
+            lhs.forEach { it.type = tpe }
+        }
         val rhs = frontend.expressionHandler.handle(node.value)
         if (rhs is List<*>)
             newAssignExpression(

cpg-language-python/src/test/kotlin/de/fraunhofer/aisec/cpg/frontends/python/statementHandler/StatementHandlerTest.kt

@@ -26,22 +26,18 @@
 package de.fraunhofer.aisec.cpg.frontends.python.statementHandler
 
 import de.fraunhofer.aisec.cpg.TranslationResult
-import de.fraunhofer.aisec.cpg.frontends.python.PythonLanguage
+import de.fraunhofer.aisec.cpg.frontends.python.*
 import de.fraunhofer.aisec.cpg.graph.*
-import de.fraunhofer.aisec.cpg.graph.statements.AssertStatement
-import de.fraunhofer.aisec.cpg.graph.statements.expressions.Literal
-import de.fraunhofer.aisec.cpg.test.analyze
-import de.fraunhofer.aisec.cpg.test.analyzeAndGetFirstTU
-import de.fraunhofer.aisec.cpg.test.assertResolvedType
+import de.fraunhofer.aisec.cpg.graph.statements.*
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.*
+import de.fraunhofer.aisec.cpg.test.*
 import java.nio.file.Path
-import kotlin.test.Test
-import kotlin.test.assertEquals
-import kotlin.test.assertNotNull
+import kotlin.test.*
 import org.junit.jupiter.api.BeforeAll
 import org.junit.jupiter.api.TestInstance
 
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
-class StatementHandlerTest {
+class StatementHandlerTest : BaseTest() {
 
     private lateinit var topLevel: Path
     private lateinit var result: TranslationResult
@@ -123,4 +119,19 @@ class StatementHandlerTest {
         assertNotNull(message, "Assert statement should have a message")
         assertEquals("Test message", message.value, "The assert message is incorrect")
     }
+
+    @Test
+    fun testTypeHints() {
+        analyzeFile("type_hints.py")
+
+        // type comments
+        val a = result.refs["a"]
+        assertNotNull(a)
+        assertEquals(with(result) { assertResolvedType("int") }, a.type)
+
+        // type annotation
+        val b = result.refs["b"]
+        assertNotNull(b)
+        assertEquals(with(result) { assertResolvedType("str") }, b.type)
+    }
 }

cpg-language-python/src/test/resources/python/type_hints.py

@@ -0,0 +1,3 @@
+a = 1 #type: int
+
+b: str