Create rule S7117: "SizedBox" should be used to add a whitespace to a layout

Co-authored-by: Marharyta <margarita.nedzelska@sonarsource.com>

rules/S7117/dart/metadata.json

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+{
+  "title": "\"SizedBox\" should be used to add a whitespace to a layout",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "2min"
+  },
+  "tags": [
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-7117",
+  "sqKey": "S7117",
+  "scope": "All",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "RELIABILITY": "MEDIUM"
+    },
+    "attribute": "EFFICIENT"
+  }
+}

rules/S7117/dart/rule.adoc

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+Use `SizedBox` instead of `Container`, when need to add a whitespace to layout.
+
+== Why is this an issue?
+
+In Flutter https://api.flutter.dev/flutter/widgets/SizedBox-class.html[`SizedBox`] represents a widget of a specified size. It is used to control the dimensions of the child widget. https://api.flutter.dev/flutter/widgets/Container-class.html[`Container`] is another Flutter widget, that doesn't only provide width and height, but also applies additional constraints, decorations, transformations, etc. Thus `Container` is a more advanced and at the same time a much heavier widget. It is recommended to not use it, if the only need is to add a whitespace. `SizedBox` is a better option for such simple cases. You can even benefit from a const constructor of a `SizedBox`, if applicable in your case.
+
+The rule reports issue on the `Container` instance creation, if:
+
+* both `width` and `heigh` are specified and there are no other parameters except optional `key`
+* `child` is specified, at least one of `width` or `heigh` is specified  and there are no other parameters except optional `key`
+
+=== What is the potential impact?
+
+A misuse of a `Container` widget may affect you performance and make the layout overly complicated.
+
+== How to fix it
+
+Replace `Container` with `SizedBox`
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,dart,diff-id=1,diff-type=noncompliant]
+----
+List<Widget> widgets(){
+  return [
+    Container(width: 4, height: 5),
+    Container(key: Key("MyWidget"), child: MyWidget(), height: 5)
+  ];
+}
+----
+
+==== Compliant solution
+
+[source,dart,diff-id=1,diff-type=compliant]
+----
+List<Widget> widgets(){
+  return [
+    SizedBox(width: 4, height: 5),
+    SizedBox(key: Key("MyWidget"), child: MyWidget(), height: 5)
+  ];
+}
+----
+
+== Resources
+
+=== Documentation
+
+* Dart Docs - https://dart.dev/tools/linter-rules/sized_box_for_whitespace[Dart Linter rule - sized_box_for_whitespace]
+* Flutter API Reference - https://api.flutter.dev/flutter/widgets/Container-class.html[widgets - Container class]
+* Flutter API Reference - https://api.flutter.dev/flutter/widgets/SizedBox-class.html[widgets - SizedBox class]
+
+ifdef::env-github,rspecator-view[]
+
+'''
+== Implementation Specification
+(visible only on this page)
+
+=== Message
+
+Use a 'SizedBox' to add whitespace to a layout.
+
+=== Highlighting
+
+`Container` constructor invocation without parameters.
+
+
+endif::env-github,rspecator-view[]

rules/S7117/metadata.json

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+{
+}