PY-83039 Don't trigger PyLiteralTypeCompletionContributor in cases like x = y.foo<caret>

It should be activated only for the simplest cases when the caret is either
inside an immediate string literal or its prefix is an unqualified reference
expression. It makes little sense trying to detect if something like
the literal string `"y.foobar"` is a possible value for `x`.

It's a relatively heavy completion contributor. It starts evaluating the type of
`x` flow-sensitively, analyzing all preceding function calls to take into
account `NoReturn`. It affects common workflows like typing out
`df = pd.` to create a new Pandas dataframe.

GitOrigin-RevId: f17fe2ce86ee100a3480a574c7f57a1bd67ec2d8

python/python-psi-impl/src/com/jetbrains/python/codeInsight/completion/PyLiteralTypeCompletionContributor.kt

@@ -18,6 +18,24 @@ import com.jetbrains.python.psi.types.PyType
 import com.jetbrains.python.psi.types.PyTypeUtil
 import com.jetbrains.python.psi.types.TypeEvalContext
 
+/**
+ * Provides literal type variants in the following cases:
+ * ```python
+ * x: Literal["foo", "bar"]
+ * x = <caret>
+ * x = fo<caret>
+ * x = "fo<caret>"
+ * ```
+ *
+ * or
+ *
+ * ```python
+ * def f(x: Literal["foo", "bar"]): ...
+ * f(<caret>)
+ * f(fo<caret>)
+ * f("fo<caret>")
+ * ```
+ */
 class PyLiteralTypeCompletionContributor : CompletionContributor() {
   init {
     extend(CompletionType.BASIC, psiElement(), PyLiteralTypeCompletionProvider())
@@ -27,6 +45,7 @@ class PyLiteralTypeCompletionContributor : CompletionContributor() {
 private class PyLiteralTypeCompletionProvider : CompletionProvider<CompletionParameters?>() {
   override fun addCompletions(parameters: CompletionParameters, context: ProcessingContext, result: CompletionResultSet) {
     val position = parameters.position.parent as? PyExpression ?: return
+    if (!(position is PyStringLiteralExpression || position is PyReferenceExpression && !position.isQualified)) return
     val typeEvalContext = TypeEvalContext.codeCompletion(position.project, position.containingFile)
 
     val mappedParameters = position.getMappedParameters(PyResolveContext.defaultContext(typeEvalContext))

python/testData/completion/literalType/noLiteralVariantsOnQualifiedReferenceInAssignmentValue.py

@@ -0,0 +1,5 @@
+from typing import Literal
+
+x: Literal["upper", "lower"]
+y = ""
+x = y.upp<caret>

python/testData/completion/literalType/noLiteralVariantsOnQualifiedReferenceInCallArgument.py

@@ -0,0 +1,8 @@
+from typing import Literal
+
+
+def f(x: Literal["upper", "lower"]):
+    pass
+
+y = ""
+f(y.up<caret>)

python/testSrc/com/jetbrains/python/PyLiteralTypeCompletionTest.kt

@@ -75,6 +75,16 @@ class PyLiteralTypeCompletionTest : PyTestCase() {
     myFixture.testCompletionVariants("nestedArgumentLists.py")
   }
 
+  // PY-83039
+  fun testNoLiteralVariantsOnQualifiedReferenceInAssignmentValue() {
+    doTestCompletionVariantsDoesNotContain("noLiteralVariantsOnQualifiedReferenceInAssignmentValue.py", "\"upper\"")
+  }
+
+  // PY-83039
+  fun testNoLiteralVariantsOnQualifiedReferenceInCallArgument() {
+    doTestCompletionVariantsDoesNotContain("noLiteralVariantsOnQualifiedReferenceInCallArgument.py", "\"upper\"")
+  }
+
   override fun getTestDataPath(): String {
     return super.getTestDataPath() + "/completion/literalType"
   }
@@ -84,4 +94,10 @@ class PyLiteralTypeCompletionTest : PyTestCase() {
     assertNotNull(result)
     assertContainsElements(result!!, *items)
   }
+
+  private fun doTestCompletionVariantsDoesNotContain(fileBefore: String, vararg items: String) {
+    val result = myFixture.getCompletionVariants(fileBefore)
+    assertNotNull(result)
+    assertDoesntContain(result!!, *items)
+  }
 }