[dotnet] Annotate nullability on Actions type

[RenderMichael]

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Annotate nullability on Actions type

Motivation and Context

Contributes to #14640

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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PR Type

Enhancement, Bug fix

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Description

• Annotated nullability across the Actions class and related methods.

• Added null checks and exception handling for method arguments.

• Improved code clarity with nullable reference types and annotations.

• Enhanced documentation with detailed exception summaries.

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Changes walkthrough 📝

	Relevant files
Enhancement	Actions.cs Nullability annotations and argument validation in `Actions.cs` dotnet/src/webdriver/Interactions/Actions.cs Enabled nullable reference types with #nullable enable. Annotated fields and method parameters with nullable types. Added null checks and ArgumentNullException for method arguments. Improved exception documentation for various methods. +48/-26
Bug fix	InputDevice.cs Add exception handling for `CreatePause` duration                dotnet/src/webdriver/Interactions/InputDevice.cs Added exception handling for negative duration in CreatePause. Updated documentation to reflect new exception. +1/-0      PauseInteraction.cs Validate duration in `PauseInteraction` constructor            dotnet/src/webdriver/Interactions/PauseInteraction.cs Added validation for negative duration in constructor. Updated documentation to include exception details. +1/-0

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PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 3 🔵🔵🔵⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Null Dereference The GetDriverAs<T> method could return null but is used directly without null check in the Actions constructor, which could lead to a NullReferenceException IActionExecutor actionExecutor = GetDriverAs<IActionExecutor>(driver) ?? throw new ArgumentException("The IWebDriver object must implement or wrap a driver that implements IActionExecutor.", nameof(driver)); Potential Bug The GetLocatableFromElement method could return null for the target variable even after the element null check, which could lead to unexpected behavior ILocatable? target = null; IWrapsElement? wrapper = element as IWrapsElement; while (wrapper != null) { target = wrapper.WrappedElement as ILocatable; wrapper = wrapper.WrappedElement as IWrapsElement;

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Validate nullable element before use Add null check for scrollOrigin.Element before using it with the '!' operator to prevent potential runtime errors. dotnet/src/webdriver/Interactions/Actions.cs [577-578] -this.actionBuilder.AddAction(this.GetActiveWheel().CreateWheelScroll(scrollOrigin.Element!, +if (scrollOrigin.Element == null) + throw new ArgumentException("Element must not be null when viewport is false.", nameof(scrollOrigin)); +this.actionBuilder.AddAction(this.GetActiveWheel().CreateWheelScroll(scrollOrigin.Element, scrollOrigin.XOffset, scrollOrigin.YOffset, deltaX, deltaY, duration)); Apply this suggestion Suggestion importance[1-10]: 9 Why: The suggestion addresses a critical issue where using the null-forgiving operator (!) without validation could cause runtime errors. Adding explicit validation improves code safety and provides better error messaging.	9
	Add missing null check Add null check for driver parameter in constructor to prevent potential NullReferenceException. dotnet/src/webdriver/Interactions/Actions.cs [55-59] public Actions(IWebDriver driver, TimeSpan duration) { + if (driver == null) + throw new ArgumentNullException(nameof(driver)); + IActionExecutor actionExecutor = GetDriverAs<IActionExecutor>(driver) ?? throw new ArgumentException("The IWebDriver object must implement or wrap a driver that implements IActionExecutor.", nameof(driver)); Apply this suggestion Suggestion importance[1-10]: 8 Why: Adding a null check for the driver parameter is crucial to prevent NullReferenceException and provide clear error messages. This is a significant improvement for API robustness and error handling.	8
Learned best practice	Use ArgumentNullException.ThrowIfNull() for more concise and standardized null parameter validation Add ArgumentNullException.ThrowIfNull() checks at the start of methods that have nullable parameters but require non-null values. For example, in the ScrollFromOrigin method, add null validation for the scrollOrigin parameter before using it. dotnet/src/webdriver/Interactions/Actions.cs [560-563] public Actions ScrollFromOrigin(WheelInputDevice.ScrollOrigin scrollOrigin, int deltaX, int deltaY) { - if (scrollOrigin is null) - { - throw new ArgumentNullException(nameof(scrollOrigin)); - } + ArgumentNullException.ThrowIfNull(scrollOrigin, nameof(scrollOrigin)); Apply this suggestion	6