KT-12299 Completion: incorrect priority of property foo over method getFoo in Kotlin-only code

#KT-12299 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/CompletionSession.kt

@@ -22,8 +22,10 @@ import com.intellij.codeInsight.completion.CompletionSorter
 import com.intellij.codeInsight.completion.CompletionUtil
 import com.intellij.codeInsight.completion.impl.CamelHumpMatcher
 import com.intellij.codeInsight.lookup.LookupElement
+import com.intellij.patterns.PatternCondition
 import com.intellij.patterns.StandardPatterns
 import com.intellij.psi.search.GlobalSearchScope
+import com.intellij.util.ProcessingContext
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.caches.resolve.*
 import org.jetbrains.kotlin.idea.codeInsight.ReferenceVariantsHelper
@@ -221,6 +223,12 @@ abstract class CompletionSession(
     }
 
     fun complete(): Boolean {
+        // we restart completion when prefix becomes "get" or "set" to ensure that properties get lower priority comparing to get/set functions (see KT-12299)
+        val prefixPattern = StandardPatterns.string().with(object : PatternCondition<String>("get or set prefix") {
+            override fun accepts(prefix: String, context: ProcessingContext?) = prefix == "get" || prefix == "set"
+        })
+        collector.restartCompletionOnPrefixChange(prefixPattern)
+
         val statisticsContext = calcContextForStatisticsInfo()
         if (statisticsContext != null) {
             collector.addLookupElementPostProcessor { lookupElement ->
@@ -250,7 +258,7 @@ abstract class CompletionSession(
     protected open fun createSorter(): CompletionSorter {
         var sorter = CompletionSorter.defaultSorter(parameters, prefixMatcher)!!
 
-        sorter = sorter.weighBefore("stats", DeprecatedWeigher, PriorityWeigher,
+        sorter = sorter.weighBefore("stats", DeprecatedWeigher, PriorityWeigher, PreferGetSetMethodsToPropertyWeigher,
                                     NotImportedWeigher(importableFqNameClassifier),
                                     NotImportedStaticMemberWeigher(importableFqNameClassifier),
                                     KindWeigher, CallableWeigher)

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/Weighers.kt

@@ -155,6 +155,19 @@ object VariableOrFunctionWeigher : LookupElementWeigher("kotlin.variableOrFuncti
     }
 }
 
+/**
+ * Decreases priority of properties when prefix starts with "get" or "set" (and the property name does not)
+ */
+object PreferGetSetMethodsToPropertyWeigher : LookupElementWeigher("kotlin.preferGetSetMethodsToProperty", false, true){
+    override fun weigh(element: LookupElement, context: WeighingContext): Int {
+        val property = (element.`object` as? DeclarationLookupObject)?.descriptor as? PropertyDescriptor ?: return 0
+        val prefixMatcher = context.itemMatcher(element)
+        if (prefixMatcher.prefixMatches(property.name.asString())) return 0
+        val matchedLookupStrings = element.allLookupStrings.filter { prefixMatcher.prefixMatches(it) }
+        if (matchedLookupStrings.all { it.startsWith("get") || it.startsWith("set") }) return 1 else return 0
+    }
+}
+
 object DeprecatedWeigher : LookupElementWeigher("kotlin.deprecated") {
     override fun weigh(element: LookupElement): Int {
         val o = element.`object` as? DeclarationLookupObject ?: return 0

idea/idea-completion/testData/weighers/basic/PreferGetMethodToProperty.Data.kt

@@ -0,0 +1,5 @@
+package dependency
+
+import test.A
+
+fun A.getFaa() = 1

idea/idea-completion/testData/weighers/basic/PreferGetMethodToProperty.kt

@@ -0,0 +1,16 @@
+package test
+
+class A {
+    val foo = 42
+
+    fun getFoo() = ""
+
+    fun test() {
+        getF<caret>
+    }
+
+}
+
+// ORDER: getFoo
+// ORDER: getFaa
+// ORDER: foo

idea/idea-completion/testData/weighers/smart/StaticMemberAndPrefix.kt

@@ -0,0 +1,10 @@
+interface Z {
+    companion object {
+        val instance: Z? = null
+    }
+}
+
+fun foo(): Z? = Z<caret>
+
+// ORDER: instance
+// ORDER: object

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/weighers/BasicCompletionWeigherTestGenerated.java

@@ -161,6 +161,12 @@ public class BasicCompletionWeigherTestGenerated extends AbstractBasicCompletion
         doTest(fileName);
     }
 
+    @TestMetadata("PreferGetMethodToProperty.kt")
+    public void testPreferGetMethodToProperty() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/PreferGetMethodToProperty.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("PropertiesBeforeKeywords.kt")
     public void testPropertiesBeforeKeywords() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/PropertiesBeforeKeywords.kt");

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/weighers/SmartCompletionWeigherTestGenerated.java

@@ -245,6 +245,12 @@ public class SmartCompletionWeigherTestGenerated extends AbstractSmartCompletion
         doTest(fileName);
     }
 
+    @TestMetadata("StaticMemberAndPrefix.kt")
+    public void testStaticMemberAndPrefix() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/smart/StaticMemberAndPrefix.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("SuperMembers.kt")
     public void testSuperMembers() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/smart/SuperMembers.kt");