PY-47254 Don't duplicate already imported module names in completion

By running the completion contributor for non-imported modules after everything
else, including the LegacyCompletionContributor offering names present in
the scope, and filtering out duplicate variants.

GitOrigin-RevId: 98982b2c33d1fc11d70b144de556a6825bd3febc

python/python-psi-impl/resources/META-INF/PythonPsiImpl.xml

@@ -120,7 +120,7 @@
                             implementationClass="com.jetbrains.python.codeInsight.completion.PyClassNameCompletionContributor"/>
     <completion.contributor language="Python"
                             implementationClass="com.jetbrains.python.codeInsight.completion.PyModulePackageCompletionContributor"/>
-    <completion.contributor language="Python"
+    <completion.contributor language="Python" order="first"
                             implementationClass="com.jetbrains.python.codeInsight.completion.PyModuleNameCompletionContributor"/>
     <completion.contributor language="Python"
                             implementationClass="com.jetbrains.python.codeInsight.completion.PyUnresolvedModuleAttributeCompletionContributor"/>

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

@@ -4,7 +4,7 @@ package com.jetbrains.python.codeInsight.completion
 import com.intellij.codeInsight.completion.CompletionContributor
 import com.intellij.codeInsight.completion.CompletionParameters
 import com.intellij.codeInsight.completion.CompletionResultSet
-import com.intellij.codeInsight.lookup.LookupElementBuilder
+import com.intellij.codeInsight.lookup.LookupElement
 import com.intellij.openapi.project.DumbAware
 import com.intellij.psi.MultiplePsiFilesPerDocumentFileViewProvider
 import com.intellij.psi.PsiDirectory
@@ -41,19 +41,24 @@ class PyModuleNameCompletionContributor : CompletionContributor(), DumbAware {
    */
   override fun fillCompletionVariants(parameters: CompletionParameters, result: CompletionResultSet) {
     if (!shouldDoCompletion(parameters)) return
-    doFillCompletionVariants(parameters, result)
+
+    val otherVariants = mutableSetOf<String>()
+    result.runRemainingContributors(parameters) {
+      otherVariants.add(it.lookupElement.lookupString)
+      result.passResult(it)
+    }
+    doFillCompletionVariants(parameters, result, otherVariants)
   }
 
-  fun doFillCompletionVariants(parameters: CompletionParameters, result: CompletionResultSet) {
-    getCompletionVariants(parameters.position.parent, parameters.originalFile).asSequence()
-      .filterIsInstance<LookupElementBuilder>()
-      .filter { result.prefixMatcher.prefixMatches(it.lookupString) }
+  private fun doFillCompletionVariants(parameters: CompletionParameters, result: CompletionResultSet, otherVariants: Set<String>) {
+    getCompletionVariants(parameters.position.parent, parameters.originalFile, otherVariants).asSequence()
+      .filterIsInstance<LookupElement>()
       .filterNot { it.lookupString.startsWith('_') }
       .forEach { result.addElement(it) }
   }
 
-  private fun getCompletionVariants(element: PsiElement, file: PsiElement): List<Any> {
-    val alreadyAddedNames = HashSet<String>()
+  private fun getCompletionVariants(element: PsiElement, file: PsiElement, otherVariants: Set<String>): List<Any> {
+    val alreadyAddedNames = HashSet<String>(otherVariants)
     val result = ArrayList<Any>()
     resolveQualifiedName(QualifiedName.fromComponents(), fromFoothold(file))
       .asSequence()

python/testData/completion/notImportedQualifiedName/AlreadyImportedModulesNotSuggestedTwice/main.py

@@ -0,0 +1,3 @@
+import foo
+
+fo<caret>

python/testSrc/com/jetbrains/python/PyNotImportedQualifiedNameCompletionTest.java

@@ -2,6 +2,7 @@
 package com.jetbrains.python;
 
 import com.intellij.psi.util.QualifiedName;
+import com.intellij.util.containers.ContainerUtil;
 import com.jetbrains.python.fixtures.PyTestCase;
 import com.jetbrains.python.psi.stubs.PyQualifiedNameCompletionMatcher.QualifiedNameMatcher;
 import org.jetbrains.annotations.Nullable;
@@ -166,6 +167,12 @@ public class PyNotImportedQualifiedNameCompletionTest extends PyTestCase {
     assertContainsElements(doBasicCompletion(), "pytest.mark", "pytest.param");
   }
 
+  // PY-47254
+  public void testAlreadyImportedModulesNotSuggestedTwice() {
+    List<String> variants = doBasicCompletion();
+    assertEquals(1, ContainerUtil.count(variants, "foo"::equals));
+  }
+
   @Nullable
   private List<String> doBasicCompletion() {
     myFixture.copyDirectoryToProject(getTestName(false), "");