Bugfix. Unused_import rule should ignore all standard operator funs

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/rules/chapter3/files/FileStructureRule.kt

@@ -73,7 +73,7 @@ class FileStructureRule(configRules: List<RulesConfig>) : DiktatRule(
         }
     private val refSet: MutableSet<String> = mutableSetOf()
     private var packageName = ""
-    private val ignoreImports = setOf("invoke", "get", "set")
+    private val ignoreImports = setOf("invoke", "get", "set", "getValue")
 
     override fun logic(node: ASTNode) {
         if (node.elementType == FILE) {
@@ -226,11 +226,9 @@ class FileStructureRule(configRules: List<RulesConfig>) : DiktatRule(
                 ) {
                     // this branch corresponds to imports from the same package
                     deleteImport(importPath, node, ktImportDirective)
-                } else if (importName != null && !ignoreImports.contains(importName) && !refSet.contains(
-                    importName
-                )
-                ) {
+                } else if (importName != null && !ignoreImports.contains(importName) && !refSet.contains(importName) && !operatorMap.containsKey(importName)) {
                     // this import is not used anywhere
+                    // Fixme: operatorMap imports and `getValue` should be deleted if unused
                     deleteImport(importPath, node, ktImportDirective)
                 }
             }

diktat-rules/src/test/kotlin/org/cqfn/diktat/ruleset/chapter3/FileStructureRuleTest.kt

@@ -13,6 +13,7 @@ import org.cqfn.diktat.util.LintTestBase
 
 import com.pinterest.ktlint.core.LintError
 import generated.WarningNames
+import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Tag
 import org.junit.jupiter.api.Test
 
@@ -394,4 +395,83 @@ class FileStructureRuleTest : LintTestBase(::FileStructureRule) {
             """.trimMargin(),
         )
     }
+
+    @Test
+    @Tag(WarningNames.UNUSED_IMPORT)
+    fun `check by #1`() {
+        lintMethod(
+            """
+                |package org.cqfn.diktat.example
+                |
+                |import com.example.get
+                |import com.example.invoke
+                |import com.example.set
+                |import kotlin.properties.Delegates
+                |
+                |fun main() {
+                |   val a by Delegates.observable()
+                |}
+            """.trimMargin(),
+        )
+    }
+
+    @Test
+    @Tag(WarningNames.UNUSED_IMPORT)
+    fun `check by #2 should not trigger`() {
+        lintMethod(
+            """
+                |package org.cqfn.diktat.example
+                |
+                |import com.example.get
+                |import com.example.invoke
+                |import com.example.set
+                |import tasks.getValue
+                |
+                |fun main() {
+                |   val a by tasks.getting
+                |}
+            """.trimMargin(),
+        )
+    }
+
+    @Test
+    @Tag(WarningNames.UNUSED_IMPORT)
+    fun `check by #3 should trigger`() {
+        lintMethod(
+            """
+                |package org.cqfn.diktat.example
+                |
+                |import Delegate
+                |import com.example.get
+                |import com.example.invoke
+                |import com.example.set
+                |
+                |fun main() {
+                |   val a
+                |}
+            """.trimMargin(),
+            LintError(1, 1, ruleId, "${Warnings.UNUSED_IMPORT.warnText()} Delegate - unused import", true)
+        )
+    }
+
+    @Disabled
+    @Test
+    @Tag(WarningNames.UNUSED_IMPORT)
+    fun `check by #4 should trigger`() {
+        lintMethod(
+            """
+                |package org.cqfn.diktat.example
+                |
+                |import com.example.get
+                |import com.example.invoke
+                |import com.example.set
+                |import tasks.getValue
+                |
+                |fun main() {
+                |   val a
+                |}
+            """.trimMargin(),
+            LintError(1, 1, ruleId, "${Warnings.UNUSED_IMPORT.warnText()} tasks.getValue - unused import", true)
+        )
+    }
 }