[dotnet] Start adding nullable reference type annotations to the Support package

[RenderMichael]

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Description

This implements nullable reference types and the requisite null checks (alongside some modernization) on the first half of the support package, as well as types in the support namespace but in the regular package.

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

• Added nullable reference type annotations across multiple files to improve null safety.
• Introduced exception handling for null arguments in constructors and methods.
• Simplified method logic and improved type checking in several classes.
• Updated project configuration to enable nullable annotations.
• Set default values for mock objects in tests to ensure consistent behavior.

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Changes walkthrough 📝

	Relevant files
Enhancement	18 files FindElementEventArgs.cs Add nullability and exception handling to FindElementEventArgs dotnet/src/support/Events/FindElementEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. Removed private fields and used auto-properties. +12/-23  GetShadowRootEventArgs.cs Add nullability and exception handling to GetShadowRootEventArgs dotnet/src/support/Events/GetShadowRootEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. Removed private fields and used auto-properties. +5/-13    WebDriverExceptionEventArgs.cs Add nullability and exception handling to WebDriverExceptionEventArgs dotnet/src/support/Events/WebDriverExceptionEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. Removed private fields and used auto-properties. +6/-14    WebDriverNavigationEventArgs.cs Add nullability and exception handling to WebDriverNavigationEventArgs dotnet/src/support/Events/WebDriverNavigationEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. Removed private fields and used auto-properties. +9/-16    WebDriverScriptEventArgs.cs Add nullability and exception handling to WebDriverScriptEventArgs dotnet/src/support/Events/WebDriverScriptEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. Removed private fields and used auto-properties. +5/-13    WebElementEventArgs.cs Add nullability and exception handling to WebElementEventArgs dotnet/src/support/Events/WebElementEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. Removed private fields and used auto-properties. +5/-13    WebElementValueEventArgs.cs Add nullability and exception handling to WebElementValueEventArgs dotnet/src/support/Events/WebElementValueEventArgs.cs Added nullability annotations to parameters and properties. Introduced exception handling for null arguments. +6/-3      WebDriverExtensions.cs Enhance WebDriverExtensions with nullability and improved logic dotnet/src/support/Extensions/WebDriverExtensions.cs Added nullability annotations to method parameters. Improved exception handling and type checking. Simplified method logic. +32/-40  LoadableComponentException.cs Add nullability annotations to LoadableComponentException dotnet/src/support/UI/LoadableComponentException.cs Added nullability annotations to constructor parameters. +2/-3      LoadableComponent{T}.cs Add nullability and improve documentation in LoadableComponent dotnet/src/support/UI/LoadableComponent{T}.cs Added nullability annotations to properties. Improved documentation comments. +10/-20  PopupWindowFinder.cs Enhance PopupWindowFinder with nullability and simplified logic dotnet/src/support/UI/PopupWindowFinder.cs Added nullability annotations to parameters. Simplified method logic. +7/-13    SlowLoadableComponent{T}.cs Add nullability and improve exception handling in SlowLoadableComponent dotnet/src/support/UI/SlowLoadableComponent{T}.cs Added nullability annotations to properties. Improved exception handling. +17/-29  UnexpectedTagNameException.cs Add nullability annotations to UnexpectedTagNameException dotnet/src/support/UI/UnexpectedTagNameException.cs Added nullability annotations to constructor parameters. +2/-3      DefaultWait{T}.cs Enhance DefaultWait with nullability and improved logic    dotnet/src/webdriver/Support/DefaultWait{T}.cs Added nullability annotations to methods and properties. Improved exception handling and type checking. +26/-51  IClock.cs Enable nullable reference types in IClock                                dotnet/src/webdriver/Support/IClock.cs Enabled nullable reference types. +2/-0      IWait{T}.cs Add nullability annotations to IWait interface                      dotnet/src/webdriver/Support/IWait{T}.cs Added nullability annotations to method signatures. +5/-1      SystemClock.cs Enable nullable reference types and simplify SystemClock  dotnet/src/webdriver/Support/SystemClock.cs Enabled nullable reference types. Simplified method logic. +5/-12    WebDriverWait.cs Enable nullable reference types and simplify WebDriverWait dotnet/src/webdriver/Support/WebDriverWait.cs Enabled nullable reference types. Simplified method logic. +4/-4
Tests	1 files EventFiringWebDriverTest.cs Set default values for mocks in EventFiringWebDriverTest  dotnet/test/support/Events/EventFiringWebDriverTest.cs Set default values for mock objects. +8/-2
Configuration changes	1 files WebDriver.Support.csproj Enable nullable annotations in project file                            dotnet/src/support/WebDriver.Support.csproj Updated project file to enable nullable annotations. +2/-0

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[RenderMichael]

The null checks found a hole in the mocking, these changes are necessary to make those tests pass.

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PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

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

🧪 PR contains tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Possible Bug The Until method may throw NullReferenceException when condition returns null for non-nullable value types Code Smell The Until method has complex branching logic that could be simplified and made more maintainable Code Smell The constructor allows null URL parameter but does not document this in XML comments

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Fix boolean result type checking to prevent potential infinite loops in wait conditions The boolean result check in the Until method is incorrect. The current code only returns when result is true, but fails to handle false values properly, which could lead to infinite loops. The check should verify if the result is actually a boolean value before evaluating it. dotnet/src/webdriver/Support/DefaultWait{T}.cs [163-166] -if (result is true) +if (result is bool boolResult) { - return result; + if (boolResult) + { + return result; + } } Apply this suggestion Suggestion importance[1-10]: 9 Why: The suggestion addresses a critical issue that could cause infinite loops in wait conditions. The current code only checks for true values but doesn't properly handle boolean type verification, which could lead to runtime errors or unexpected behavior.	9
	Ensure consistency between method signature nullability annotations to prevent potential null reference exceptions The return value is marked as non-null with [return: NotNull] but the input parameter allows null values (TResult?). This could lead to runtime errors if null is returned. Either remove NotNull attribute or ensure the condition function cannot return null. dotnet/src/webdriver/Support/IWait{T}.cs [63-64] -[return: NotNull] -TResult Until<TResult>(Func<T, TResult?> condition); +TResult Until<TResult>(Func<T, TResult> condition) where TResult : notnull; Apply this suggestion Suggestion importance[1-10]: 9 Why: The suggestion identifies a critical inconsistency in null handling that could lead to runtime exceptions. The current implementation has contradicting nullability annotations which is a significant issue for type safety.	9
General	Enable full null reference type checking to catch potential null reference exceptions at compile time Setting Nullable to 'annotations' only enables nullable warning annotations but does not enforce null checks. For full null safety, use 'enable' instead. dotnet/src/webdriver/Support/WebDriver.Support.csproj [9] -<Nullable>annotations</Nullable> +<Nullable>enable</Nullable> Apply this suggestion Suggestion importance[1-10]: 8 Why: This is a valuable suggestion as enabling full null checking would provide stronger compile-time guarantees against null reference exceptions, which aligns with the PR's focus on improving null safety.	8
	Improve error message clarity by including the actual type received in exception messages The null check for responseObject should include a more specific error message that includes the actual type received, to help with debugging unexpected response formats. dotnet/src/support/Extensions/WebDriverExtensions.cs [54-57] if (responseObject is not Response screenshotResponse) { - throw new WebDriverException($"Unexpected failure getting screenshot; response was not in the proper format: {responseObject}"); + throw new WebDriverException($"Unexpected failure getting screenshot; response was not in the proper format. Expected Response type but got: {responseObject?.GetType().FullName ?? "null"}"); } Apply this suggestion Suggestion importance[1-10]: 4 Why: The suggestion improves error message diagnostics by including the actual type of the unexpected response, which would help with debugging. While useful, this is a minor enhancement to error reporting rather than a critical functionality fix.	4

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[nvborisenko]

Even don't spend your time on Support package, it is kind of unsupported.

[RenderMichael]

@nvborisenko I get it 😁

But it's so small, and so simple to get it working. This PR does most of the work.

The EventFiringWebDriver is the single remaining file, which I left out of this PR so it doesn't get too big. I can include it in this one, if that simplifies things.