PY-19292 PY-14176 Optimize Imports doesn't re-create unaffected import statements

For instance, "from" import statements where imported names are already
ordered. Otherwise even when all imports are well formed, the whole
import block will be inserted anew and reformatted.

python/src/com/jetbrains/python/codeInsight/imports/PyImportOptimizer.java

@@ -147,27 +147,30 @@ public class PyImportOptimizer implements ImportOptimizer {
           final PyFromImportStatement fromImportStatement = (PyFromImportStatement)statement;
           final QualifiedName source = fromImportStatement.getImportSourceQName();
           final String sourceText = Objects.toString(source, "");
-          if (myPySettings.OPTIMIZE_IMPORTS_JOIN_FROM_IMPORTS_WITH_SAME_SOURCE) {
-            final Collection<PyFromImportStatement> sameSourceImports = fromImportSources.get(source);
-            if (!sameSourceImports.isEmpty()) {
-              final List<PyImportElement> allImportElements = new ArrayList<>();
-              for (PyFromImportStatement sameSourceImport : sameSourceImports) {
-                ContainerUtil.addAll(allImportElements, sameSourceImport.getImportElements());
-              }
-              if (myPySettings.OPTIMIZE_IMPORTS_SORT_NAMES_IN_FROM_IMPORTS) {
-                Collections.sort(allImportElements, IMPORT_ELEMENT_COMPARATOR);
-              }
-              final String importedNames = StringUtil.join(allImportElements, PsiElement::getText, ", ");
-              result.add(generator.createFromImportStatement(langLevel, sourceText, importedNames, null));
-  
-              // remember that we have checked imports from this source already 
-              fromImportSources.remove(source);
+          final Collection<PyFromImportStatement> sameSourceImports = fromImportSources.get(source);
+          if (sameSourceImports.isEmpty()) continue;
+
+          final List<PyImportElement> newStatementElements = new ArrayList<>();
+          // Join multiple "from" imports with the same source, like "from module import foo; from module import bar as b"
+          if (myPySettings.OPTIMIZE_IMPORTS_JOIN_FROM_IMPORTS_WITH_SAME_SOURCE && sameSourceImports.size() > 1) {
+            for (PyFromImportStatement sameSourceImport : sameSourceImports) {
+              ContainerUtil.addAll(newStatementElements, sameSourceImport.getImportElements());
             }
+            // Remember that we have checked imports with this source already 
+            fromImportSources.remove(source);
           }
           else if (myPySettings.OPTIMIZE_IMPORTS_SORT_NAMES_IN_FROM_IMPORTS) {
-            final PyImportElement[] importElements = fromImportStatement.getImportElements();
-            Arrays.sort(importElements, IMPORT_ELEMENT_COMPARATOR);
-            final String importedNames = StringUtil.join(importElements, PsiElement::getText, ", ");
+            final List<PyImportElement> originalElements = Arrays.asList(fromImportStatement.getImportElements());
+            if (!Ordering.from(IMPORT_ELEMENT_COMPARATOR).isOrdered(originalElements)) {
+              ContainerUtil.addAll(newStatementElements, originalElements);
+            }
+          }
+
+          if (!newStatementElements.isEmpty()) {
+            if (myPySettings.OPTIMIZE_IMPORTS_SORT_NAMES_IN_FROM_IMPORTS) {
+              Collections.sort(newStatementElements, IMPORT_ELEMENT_COMPARATOR);
+            }
+            final String importedNames = StringUtil.join(newStatementElements, PsiElement::getText, ", ");
             result.add(generator.createFromImportStatement(langLevel, sourceText, importedNames, null));
           }
           else {

python/testData/optimizeImports/joinFromImportsDoesntAffectSingleImports.after.py

@@ -0,0 +1,6 @@
+# Optimize imports should not reformat unaffected statements
+from module1 import a, b
+
+from module2 import A, B
+
+print(A, B, a, b)

python/testData/optimizeImports/joinFromImportsDoesntAffectSingleImports.py

@@ -0,0 +1,6 @@
+# Optimize imports should not reformat unaffected statements
+from module1 import a, b
+
+from module2 import A, B
+
+print(A, B, a, b)

python/testData/optimizeImports/orderNamesInsightFromImportDoesntAffectAlreadyOrderedImports.after.py

@@ -0,0 +1,6 @@
+# Optimize Imports should not re-create imports statements that are in order
+from module1 import a, b, c
+
+from module2 import A, B, C
+
+print(A, B, C, a, b, c)

python/testData/optimizeImports/orderNamesInsightFromImportDoesntAffectAlreadyOrderedImports.py

@@ -0,0 +1,6 @@
+# Optimize Imports should not re-create imports statements that are in order
+from module1 import a, b, c
+
+from module2 import A, B, C
+
+print(A, B, C, a, b, c)

python/testSrc/com/jetbrains/python/PyOptimizeImportsTest.java

@@ -145,6 +145,12 @@ public class PyOptimizeImportsTest extends PyTestCase {
     doTest();
   }
 
+  // PY-18792, PY-19292
+  public void testOrderNamesInsightFromImportDoesntAffectAlreadyOrderedImports() {
+    getPythonCodeStyleSettings().OPTIMIZE_IMPORTS_SORT_NAMES_IN_FROM_IMPORTS = true;
+    doTest();
+  }
+
   // PY-18792, PY-12926
   public void testJoinFromImportsForSameSource() {
     getPythonCodeStyleSettings().OPTIMIZE_IMPORTS_JOIN_FROM_IMPORTS_WITH_SAME_SOURCE = true;
@@ -158,6 +164,12 @@ public class PyOptimizeImportsTest extends PyTestCase {
     doTest();
   }
 
+  // PY-18792, PY-12926
+  public void testJoinFromImportsDoesntAffectSingleImports() {
+    getPythonCodeStyleSettings().OPTIMIZE_IMPORTS_JOIN_FROM_IMPORTS_WITH_SAME_SOURCE = true;
+    doTest();
+  }
+
   private void doTest() {
     myFixture.configureByFile(getTestName(true) + ".py");
     OptimizeImportsAction.actionPerformedImpl(DataManager.getInstance().getDataContext(myFixture.getEditor().getContentComponent()));