Fixes in code style, update documentation

diktat-rules/src/main/kotlin/org/cqfn/diktat/ruleset/constants/Warnings.kt

@@ -17,7 +17,7 @@ typealias ListOfPairs = MutableList<Pair<ASTNode, String>>
 /**
  * This class represent individual inspections of diktat code style.
  * A [Warnings] entry contains rule name, warning message and is used in code check.
- * @property canBeAutoCorrected whether this inspection can automatically fix the code
+ * @property canBeAutoCorrected whether this inspection can automatically fix the code. Should be public to be able to use it in docs generator.
  * @property ruleId number of the inspection according to []diktat code style](https://www.cqfn.org/diKTat/info/guide/diktat-coding-convention.html)
  */
 @Suppress(
@@ -28,7 +28,7 @@ typealias ListOfPairs = MutableList<Pair<ASTNode, String>>
     "WRONG_NEWLINES"
 )
 enum class Warnings(
-    private val canBeAutoCorrected: Boolean,
+    @Suppress("PRIVATE_MEMBER") val canBeAutoCorrected: Boolean,
     val ruleId: String,
     private val warn: String) : Rule {
     // ======== dummy test warning ======

info/build.gradle.kts

@@ -4,32 +4,51 @@ import org.cqfn.diktat.generation.docs.generateFullDoc
 import org.cqfn.diktat.generation.docs.generateRulesMapping
 
 tasks.register("generateRulesMapping") {
+    group = "documentation"
+    description = "Generates a table (rules-mapping.md), which maps warning names to chapters in code style"
     doFirst {
         generateRulesMapping()
     }
 }
 
 tasks.register("generateFullDoc") {
+    group = "documentation"
+    description = "Compile individual chapters into a single markdown document"
     doFirst {
         generateFullDoc(file("$rootDir/guide"), "diktat-coding-convention.md")
     }
 }
 
 tasks.register("generateAvailableRules") {
+    group = "documentation"
+    description = "Generate table for White paper based on available-rules.md and rules-mapping.md"
     dependsOn("generateRulesMapping")
     doFirst {
         generateAvailableRules(rootDir, file("$rootDir/../wp"))
     }
 }
 
 tasks.register("generateCodeStyle") {
+    group = "documentation"
+    description = "Adds/updates diktat code style in white paper document"
     dependsOn("generateFullDoc")
     doFirst {
         generateCodeStyle(file("$rootDir/guide"), file("$rootDir/../wp"))
     }
 }
 
+tasks.register("updateMarkdownDocumentation") {
+    group = "documentation"
+    description = "Task that aggregates all documentation updates without white paper updates"
+    dependsOn(
+        "generateRulesMapping",
+        "generateFullDoc"
+    )
+}
+
 tasks.register("updateDocumentation") {
+    group = "documentation"
+    description = "Task that aggregates all documentation updates"
     dependsOn(
         "generateRulesMapping",
         "generateAvailableRules",

info/buildSrc/build.gradle.kts

@@ -3,7 +3,12 @@ plugins {
 }
 
 repositories {
-    mavenLocal()
+    mavenCentral()
+    mavenLocal {
+        content {
+            includeGroup("org.cqfn.diktat")
+        }
+    }
     flatDir {
         dirs(
             "$rootDir/../../diktat-rules/target",

info/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.9-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

info/guide/diktat-coding-convention.md

@@ -65,6 +65,9 @@ I [Preface](#c0)
  * [3.15 Strings](#c3.15)
      * [3.15.1 Concatenation of Strings](#r3.15.1)
      * [3.15.2 String template format](#r3.15.2)
+ * [3.16 Conditional statements](#c3.16)
+     * [3.16.1 Collapsing redundant nested if-statements](#r3.16.1)
+     * [3.16.2 Too complex conditions](#r3.16.2)
 
 [4. Variables and types](#c4)
 * [4.1 Variables](#c4.1)
@@ -114,7 +117,9 @@ I [Preface](#c0)
 * [6.3 Interfaces](#c6.3)            
 * [6.4 Objects](#c6.4)      
     * [6.4.1 Instead of using utility classes/objects, use extensions](#r6.4.1)
-    * [6.4.2 Objects should be used for Stateless Interfaces](#r6.4.2) 
+    * [6.4.2 Objects should be used for Stateless Interfaces](#r6.4.2)
+* [6.5 Kts Files](#c6.5)
+    * [6.5.1 kts files should wrap logic into top-level scope](#r6.5.1)
 
 
 # Diktat Coding Style Guide
@@ -228,6 +233,7 @@ The only exception is function names in `Unit tests.`
  @Test fun `my test`() { /*...*/ }
 ``` 
 6.  The following table contains some characters that may cause confusion. Be careful when using them as identifiers. To avoid issues, use other names instead.
+
 | Expected      | Confusing name           | Suggested name   |
 | ------------- | ------------------------ | ---------------- |
 | 0 (zero)      | O, D                     | obj, dgt         |
@@ -857,13 +863,14 @@ If the classes are meant to be used externally, and are not referenced inside th
 - Companion object
 
 **Exception:**
-All variants of a `(private) val` logger should be placed at the beginning of the class (`(private) val log`, `LOG`, `logger`, etc.).
+All variants of a `private val` logger should be placed at the beginning of the class (`private val log`, `LOG`, `logger`, etc.).
 
 #### <a name="r3.1.5"></a> 3.1.5 Order of declaration of top-level code structures
 Kotlin allows several top-level declaration types: classes, objects, interfaces, properties and functions.
 When declaring more than one class or zero classes (e.g. only functions), as per rule [2.2.1](#r2.2.1), you should document the whole file in the header KDoc.
 When declaring top-level structures, keep the following order:
 1. Top-level constants and properties (following same order as properties inside a class: `const val`,`val`, `lateinit var`, `var`)
+2. typealiases (grouped by their visibility modifiers)
 2. Interfaces, classes and objects (grouped by their visibility modifiers)
 3. Extension functions
 4. Other functions
@@ -879,6 +886,8 @@ const val CONSTANT = 42
 
 val topLevelProperty = "String constant"
 
+internal typealias ExamplesHandler = (IExample) -> Unit
+
 interface IExample
 
 class Example : IExample
@@ -1086,7 +1095,7 @@ class A
 Avoid empty blocks, and ensure braces start on a new line. An empty code block can be closed immediately on the same line and the next line. However, a newline is recommended between opening and closing braces `{}` (see the examples below.)
 
 Generally, empty code blocks are prohibited; using them is considered a bad practice (especially for catch block).
-They are only appropriate for overridden functions when the base class's functionality is not needed in the class-inheritor.
+They are appropriate for overridden functions, when the base class's functionality is not needed in the class-inheritor, for lambdas used as a function and for empty function in implementation of functional interface. 
 ```kotlin
 override fun foo() {    
 }
@@ -1099,6 +1108,8 @@ fun doNothing() {}
 
 fun doNothingElse() {
 }
+
+fun foo(bar: () -> Unit = {})
 ```
 
 **Invalid examples:**
@@ -1598,6 +1609,24 @@ val socialSecurityNumber = 999_99_9999L
 val hexBytes = 0xFF_EC_DE_5E
 val bytes = 0b11010010_01101001_10010100_10010010
 ```
+#### <a name="r3.14.3"></a> 3.14.3: Magic number
+Prefer defining constants with clear names describing what the magic number means.
+**Valid example**:
+```kotlin
+class Person() {
+    fun isAdult(age: Int): Boolean = age >= majority
+
+    companion object {
+        private const val majority = 18
+    }
+}
+```
+**Invalid example**:
+```kotlin
+class Person() {
+    fun isAdult(age: Int): Boolean = age >= 18
+}
+```
 
 <!-- =============================================================================== -->
 ### <a name="c3.15"></a> 3.15 Strings
@@ -1647,6 +1676,75 @@ val someString = "$myArgument"
 ```kotlin
 val someString = myArgument
 ```
+
+<!-- =============================================================================== -->
+### <a name="c3.16"></a> 3.16 Conditional Statements
+This section describes the general rules related to the сonditional statements.
+
+#### <a name="r3.16.1"></a> 3.16.1 Collapsing redundant nested if-statements
+The nested if-statements, when possible, should be collapsed into a single one
+by concatenating their conditions with the infix operator &&.
+
+This improves the readability by reducing the number of the nested language constructs.
+
+#### Simple collapse
+
+**Invalid example**:
+```kotlin
+if (cond1) {
+    if (cond2) {
+        doSomething()
+    }
+}
+```
+
+**Valid example**:
+```kotlin
+if (cond1 && cond2) {
+    doSomething()
+}
+```
+
+#### Compound conditions
+
+**Invalid example**:
+```kotlin
+if (cond1) {
+    if (cond2 || cond3) {
+        doSomething()
+    }
+}
+```
+
+**Valid example**:
+```kotlin
+if (cond1 && (cond2 || cond3)) {
+    doSomething()
+}
+```
+#### <a name="r3.16.2"></a> 3.16.2 Too complex conditions
+Too complex conditions should be simplified according to boolean algebra rules, if it is possible.
+The following rules are considered when simplifying an expression:
+* boolean literals are removed (e.g. `foo() || false` -> `foo()`)
+* double negation is removed (e.g. `!(!a)` -> `a`)
+* expression with the same variable are simplified (e.g. `a && b && a` -> `a && b`)
+* remove expression from disjunction, if they are subset of other expression (e.g. `a || (a && b)` -> `a`)
+* remove expression from conjunction, if they are more broad than other expression (e.g. `a && (a || b)` -> `a`)
+* de Morgan's rule (negation is moved inside parentheses, i.e. `!(a || b)` -> `!a && !b`)
+
+**Valid example**
+```kotlin
+if (condition1 && condition2) {
+    foo()
+}
+```
+
+**Invalid example**
+```kotlin
+if (condition1 && condition2 && condition1) {
+    foo()
+}
+```
 # <a name="c4"></a> 4. Variables and types
 This section is dedicated to the rules and recommendations for using variables and types in your code.
 <!-- =============================================================================== -->
@@ -2496,8 +2594,9 @@ It is recommended that for classes, the non-tightly coupled functions, which are
 They should be implemented in the same class/file where they are used. This is a non-deterministic rule, so the code cannot be checked or fixed automatically by a static analyzer.
 
 #### <a name="r6.2.2"></a> 6.2.2 No extension functions with the same name and signature if they extend base and inheritor classes (possible_bug)
-You should have ho extension functions with the same name and signature if they extend base and inheritor classes (possible_bug).esolved statically. There could be a situation when a developer implements two extension functions: one is for the base class and another for the inheritor.
-This can lead to an issue when an incorrect method is used.
+You should avoid declaring extension functions with the same name and signature if their receivers are base and inheritor classes (possible_bug),
+as extension functions are resolved statically. There could be a situation when a developer implements two extension functions: one is for the base class and
+another for the inheritor. This can lead to an issue when an incorrect method is used.
 
 **Invalid example**:
 ```kotlin
@@ -2577,7 +2676,8 @@ object O: I {
     override fun foo() {}
 }
 ```
-
+### <a name="c6.5"></a> 6.5 Kts Files
+This section describes general rules for `.kts` files
 #### <a name="r6.5.1"></a> 6.5.1 kts files should wrap logic into top-level scope
 It is still recommended wrapping logic inside functions and avoid using top-level statements for function calls or wrapping blocks of code
 in top-level scope functions like `run`.

info/guide/guide-chapter-3.md

@@ -936,18 +936,25 @@ if (cond1 && (cond2 || cond3)) {
 }
 ```
 #### <a name="r3.16.2"></a> 3.16.2 Too complex conditions
-Too complex conditions should be simplified according to boolean algebra rules, if it is possible
+Too complex conditions should be simplified according to boolean algebra rules, if it is possible.
+The following rules are considered when simplifying an expression:
+* boolean literals are removed (e.g. `foo() || false` -> `foo()`)
+* double negation is removed (e.g. `!(!a)` -> `a`)
+* expression with the same variable are simplified (e.g. `a && b && a` -> `a && b`)
+* remove expression from disjunction, if they are subset of other expression (e.g. `a || (a && b)` -> `a`)
+* remove expression from conjunction, if they are more broad than other expression (e.g. `a && (a || b)` -> `a`)
+* de Morgan's rule (negation is moved inside parentheses, i.e. `!(a || b)` -> `!a && !b`)
 
 **Valid example**
 ```kotlin
-if (cond1 && cond2) {
+if (condition1 && condition2) {
     foo()
 }
 ```
 
 **Invalid example**
 ```kotlin
-if (cond1 && cond2 && cond1) {
+if (condition1 && condition2 && condition1) {
     foo()
 }
 ```

info/guide/guide-chapter-6.md

@@ -387,8 +387,9 @@ It is recommended that for classes, the non-tightly coupled functions, which are
 They should be implemented in the same class/file where they are used. This is a non-deterministic rule, so the code cannot be checked or fixed automatically by a static analyzer.
 
 #### <a name="r6.2.2"></a> 6.2.2 No extension functions with the same name and signature if they extend base and inheritor classes (possible_bug)
-You should have ho extension functions with the same name and signature if they extend base and inheritor classes (possible_bug).esolved statically. There could be a situation when a developer implements two extension functions: one is for the base class and another for the inheritor.
-This can lead to an issue when an incorrect method is used.
+You should avoid declaring extension functions with the same name and signature if their receivers are base and inheritor classes (possible_bug),
+as extension functions are resolved statically. There could be a situation when a developer implements two extension functions: one is for the base class and
+another for the inheritor. This can lead to an issue when an incorrect method is used.
 
 **Invalid example**:
 ```kotlin

info/rules-mapping.md

@@ -57,10 +57,12 @@
 | FILE_NO_BLANK_LINE_BETWEEN_BLOCKS | [3.1.2](guide/diktat-coding-convention.md#r3.1.2) | yes | General |
 | FILE_UNORDERED_IMPORTS | [3.1.2](guide/diktat-coding-convention.md#r3.1.2) | yes | General |
 | FILE_WILDCARD_IMPORTS | [3.1.2](guide/diktat-coding-convention.md#r3.1.2) | no | General |
+| UNUSED_IMPORT | [3.1.2](guide/diktat-coding-convention.md#r3.1.2) | yes | General |
 | FILE_NAME_MATCH_CLASS | [3.1.2](guide/diktat-coding-convention.md#r3.1.2) | yes | General |
 | WRONG_ORDER_IN_CLASS_LIKE_STRUCTURES | [3.1.4](guide/diktat-coding-convention.md#r3.1.4) | yes | General |
 | BLANK_LINE_BETWEEN_PROPERTIES | [3.1.4](guide/diktat-coding-convention.md#r3.1.4) | yes | General |
 | WRONG_DECLARATIONS_ORDER | [3.1.4](guide/diktat-coding-convention.md#r3.1.4) | yes | General |
+| TOP_LEVEL_ORDER | [3.1.5](guide/diktat-coding-convention.md#r3.1.5) | yes | General |
 | NO_BRACES_IN_CONDITIONALS_AND_LOOPS | [3.2.1](guide/diktat-coding-convention.md#r3.2.1) | yes | General |
 | BRACES_BLOCK_STRUCTURE_ERROR | [3.2.2](guide/diktat-coding-convention.md#r3.2.2) | yes | General |
 | WRONG_INDENTATION | [3.3.1](guide/diktat-coding-convention.md#r3.3.1) | yes | General |
@@ -69,7 +71,9 @@
 | MORE_THAN_ONE_STATEMENT_PER_LINE | [3.6.1](guide/diktat-coding-convention.md#r3.6.1) | yes | General |
 | REDUNDANT_SEMICOLON | [3.6.2](guide/diktat-coding-convention.md#r3.6.2) | yes | General |
 | WRONG_NEWLINES | [3.6.2](guide/diktat-coding-convention.md#r3.6.2) | yes | General |
+| TRAILING_COMMA | [3.6.2](guide/diktat-coding-convention.md#r3.6.2) | yes | General |
 | COMPLEX_EXPRESSION | [3.6.3](guide/diktat-coding-convention.md#r3.6.3) | no | General |
+| COMPLEX_BOOLEAN_EXPRESSION | [3.6.4](guide/diktat-coding-convention.md#r3.6.4) | yes | General |
 | TOO_MANY_BLANK_LINES | [3.7.1](guide/diktat-coding-convention.md#r3.7.1) | yes | General |
 | WRONG_WHITESPACE | [3.8.1](guide/diktat-coding-convention.md#r3.8.1) | yes | General |
 | TOO_MANY_CONSECUTIVE_SPACES | [3.8.1](guide/diktat-coding-convention.md#r3.8.1) | yes | General |
@@ -79,9 +83,11 @@
 | ANNOTATION_NEW_LINE | [3.12.1](guide/diktat-coding-convention.md#r3.12.1) | yes | General |
 | WRONG_MULTIPLE_MODIFIERS_ORDER | [3.14.1](guide/diktat-coding-convention.md#r3.14.1) | yes | General |
 | LONG_NUMERICAL_VALUES_SEPARATED | [3.14.2](guide/diktat-coding-convention.md#r3.14.2) | yes | General |
-| STRING_CONCATENATION | [3.15.1](guide/diktat-coding-convention.md#r3.15.1) | no | General |
+| MAGIC_NUMBER | [3.14.3](guide/diktat-coding-convention.md#r3.14.3) | no | General |
+| STRING_CONCATENATION | [3.15.1](guide/diktat-coding-convention.md#r3.15.1) | yes | General |
 | STRING_TEMPLATE_CURLY_BRACES | [3.15.2](guide/diktat-coding-convention.md#r3.15.2) | yes | General |
 | STRING_TEMPLATE_QUOTES | [3.15.2](guide/diktat-coding-convention.md#r3.15.2) | yes | General |
+| COLLAPSE_IF_STATEMENTS | [3.16.1](guide/diktat-coding-convention.md#r3.16.1) | yes | General |
 | FLOAT_IN_ACCURATE_CALCULATIONS | [4.1.1](guide/diktat-coding-convention.md#r4.1.1) | no | Variables |
 | SAY_NO_TO_VAR | [4.1.3](guide/diktat-coding-convention.md#r4.1.3) | no | Variables |
 | SMART_CAST_NEEDED | [4.2.1](guide/diktat-coding-convention.md#r4.2.1) | yes | Variables |
@@ -98,6 +104,7 @@
 | WRONG_OVERLOADING_FUNCTION_ARGUMENTS | [5.2.3](guide/diktat-coding-convention.md#r5.2.3) | no | Functions |
 | RUN_BLOCKING_INSIDE_ASYNC | [5.2.4](guide/diktat-coding-convention.md#r5.2.4) | no | Functions |
 | TOO_MANY_LINES_IN_LAMBDA | [5.2.5](guide/diktat-coding-convention.md#r5.2.5) | no | Functions |
+| CUSTOM_LABEL | [5.2.6](guide/diktat-coding-convention.md#r5.2.6) | no | Functions |
 | SINGLE_CONSTRUCTOR_SHOULD_BE_PRIMARY | [6.1.1](guide/diktat-coding-convention.md#r6.1.1) | yes | Classes |
 | USE_DATA_CLASS | [6.1.2](guide/diktat-coding-convention.md#r6.1.2) | no | Classes |
 | EMPTY_PRIMARY_CONSTRUCTOR | [6.1.3](guide/diktat-coding-convention.md#r6.1.3) | yes | Classes |
@@ -109,6 +116,9 @@
 | WRONG_NAME_OF_VARIABLE_INSIDE_ACCESSOR | [6.1.9](guide/diktat-coding-convention.md#r6.1.9) | no | Classes |
 | TRIVIAL_ACCESSORS_ARE_NOT_RECOMMENDED | [6.1.10](guide/diktat-coding-convention.md#r6.1.10) | yes | Classes |
 | COMPACT_OBJECT_INITIALIZATION | [6.1.11](guide/diktat-coding-convention.md#r6.1.11) | yes | Classes |
+| INLINE_CLASS_CAN_BE_USED | [6.1.12](guide/diktat-coding-convention.md#r6.1.12) | yes | Classes |
 | EXTENSION_FUNCTION_SAME_SIGNATURE | [6.2.2](guide/diktat-coding-convention.md#r6.2.2) | no | Classes |
+| EXTENSION_FUNCTION_WITH_CLASS | [6.2.3](guide/diktat-coding-convention.md#r6.2.3) | no | Classes |
 | AVOID_USING_UTILITY_CLASS | [6.4.1](guide/diktat-coding-convention.md#r6.4.1) | no | Classes |
-| OBJECT_IS_PREFERRED | [6.4.2](guide/diktat-coding-convention.md#r6.4.2) | yes | Classes |
+| OBJECT_IS_PREFERRED | [6.4.2](guide/diktat-coding-convention.md#r6.4.2) | yes | Classes |
+| RUN_IN_SCRIPT | [6.5.1](guide/diktat-coding-convention.md#r6.5.1) | yes | Classes |