Allow underscore in packages and forbid uppercase letters (KT-27900)

idea/src/org/jetbrains/kotlin/idea/inspections/NamingConventionInspections.kt

@@ -16,6 +16,7 @@ import com.intellij.psi.PsiElementVisitor
 import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.ui.EditorTextField
 import com.siyeh.ig.psiutils.TestUtils
+import org.intellij.lang.annotations.Language
 import org.intellij.lang.regexp.RegExpFileType
 import org.jetbrains.kotlin.idea.quickfix.RenameIdentifierFix
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -56,9 +57,13 @@ private val NO_BAD_CHARACTERS_OR_UNDERSCORE = NamingRule("may contain only lette
     it.any { c -> c !in 'a'..'z' && c !in 'A'..'Z' && c !in '0'..'9' && c != '_' }
 }
 
+private val ONLY_LOWER_DIGITS_OR_UNDERSCORE = NamingRule("may contain only lowercase letters, digits or underscores") {
+    it.any { c -> c !in 'a'..'z' && c !in '0'..'9' && c != '_' }
+}
+
 abstract class NamingConventionInspection(
     private val entityName: String,
-    private val defaultNamePattern: String,
+    @Language("RegExp") private val defaultNamePattern: String,
     private vararg val rules: NamingRule
 ) : AbstractKotlinInspection() {
     protected var nameRegex: Regex? = defaultNamePattern.toRegex()
@@ -228,7 +233,7 @@ class LocalVariableNameInspection :
     )
 
 class PackageNameInspection :
-    NamingConventionInspection("Package", "[a-z][A-Za-z\\d]*(\\.[a-z][A-Za-z\\d]*)*", NO_UNDERSCORES) {
+    NamingConventionInspection("Package", "[a-z_][a-z\\d_]*(\\.[a-z_][a-z\\d_]*)*", ONLY_LOWER_DIGITS_OR_UNDERSCORE) {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor {
         return packageDirectiveVisitor { directive ->
             val qualifiedName = directive.qualifiedName

idea/testData/inspections/naming/package/allLowerCase.kt

@@ -0,0 +1 @@
+package one.two.three

idea/testData/inspections/naming/package/hasUpperCase.kt

@@ -0,0 +1 @@
+package one.two.Three

idea/testData/inspections/naming/package/inspectionData/expected.xml

@@ -0,0 +1,7 @@
+<problems>
+    <problem>
+        <file>hasUpperCase.kt</file>
+        <line>1</line>
+        <description>Package name &lt;code&gt;one.two.Three&lt;/code&gt; doesn't match regex '[a-z][A-Za-z\d]*_?(\.[a-z][A-Za-z\d]*_?)*' #loc</description>
+    </problem>
+</problems>

idea/testData/inspections/naming/package/inspectionData/inspections.test

@@ -0,0 +1 @@
+// INSPECTION_CLASS: org.jetbrains.kotlin.idea.inspections.PackageNameInspection

idea/testData/inspections/naming/package/keywordUnderscore.kt

@@ -0,0 +1 @@
+package com.fun_.test

idea/testData/inspections/naming/package/midleUnderscore.kt

@@ -0,0 +1 @@
+package org.so_so.example

idea/testData/inspections/naming/package/startWithUnderscoreAndDigits.kt

@@ -0,0 +1 @@
+package com.example._123name

idea/tests/org/jetbrains/kotlin/idea/codeInsight/InspectionTestGenerated.java

@@ -239,6 +239,11 @@ public class InspectionTestGenerated extends AbstractInspectionTest {
             runTest("idea/testData/inspections/naming/objectProperty/inspectionData/inspections.test");
         }
 
+        @TestMetadata("naming/package/inspectionData/inspections.test")
+        public void testNaming_package_inspectionData_Inspections_test() throws Exception {
+            runTest("idea/testData/inspections/naming/package/inspectionData/inspections.test");
+        }
+
         @TestMetadata("naming/privateProperty/inspectionData/inspections.test")
         public void testNaming_privateProperty_inspectionData_Inspections_test() throws Exception {
             runTest("idea/testData/inspections/naming/privateProperty/inspectionData/inspections.test");