[dotnet] Annotate nullability on Navigate() and SwitchTo()

[RenderMichael]

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Annotate nullability on Navigate() and SwitchTo()

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

• Enabled nullable reference types in multiple files for better null safety.

• Added ArgumentNullException checks for method parameters to improve error handling.

• Updated Navigator and TargetLocator classes to use readonly fields and sealed classes.

• Improved exception messages and type safety in Frame and Window methods.

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Changes walkthrough 📝

Relevant files

Enhancement

INavigation.cs Add nullability annotations and exceptions in `INavigation` dotnet/src/webdriver/INavigation.cs Enabled nullable reference types. Added ArgumentNullException for GoToUrl and GoToUrlAsync methods. Improved documentation with exception details. +6/-0      ITargetLocator.cs Add nullability annotations and exceptions in `ITargetLocator` dotnet/src/webdriver/ITargetLocator.cs Enabled nullable reference types. Added ArgumentNullException for Frame and Window methods. Improved exception handling with detailed messages. +8/-0      Navigator.cs Enhance null safety and immutability in `Navigator`            dotnet/src/webdriver/Navigator.cs Enabled nullable reference types. Added ArgumentNullException for constructor and GoToUrl methods. Updated driver field to readonly and class to sealed. +10/-3    TargetLocator.cs Enhance null safety and immutability in `TargetLocator`    dotnet/src/webdriver/TargetLocator.cs Enabled nullable reference types. Added ArgumentNullException for constructor and Frame/Window methods. Improved exception messages and type safety in Frame method. Updated driver field to readonly and class to sealed. +25/-11

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PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Potential Race Condition The GoToUrl method uses Task.Run to execute asynchronous code synchronously, which could lead to race conditions or deadlocks. Consider using async/await pattern consistently. Task.Run(async delegate { Null Check Ordering The Frame method checks elementReference for null after trying to cast it, which could be reordered for better efficiency and clarity. IWebDriverObjectReference? elementReference = frameElement as IWebDriverObjectReference; if (elementReference == null)

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Fix unsafe async operation pattern The GoToUrl(string url) method uses Task.Run without proper exception handling, which could swallow exceptions. Implement proper async/await pattern. dotnet/src/webdriver/Navigator.cs [90-93] public void GoToUrl(string url) { - Task.Run(async delegate - { + if (url == null) + throw new ArgumentNullException(nameof(url)); + this.GoToUrlAsync(url).GetAwaiter().GetResult(); Apply this suggestion Suggestion importance[1-10]: 9 Why: The suggestion fixes a significant issue with async/await pattern implementation that could hide exceptions and cause unexpected behavior. The proposed solution properly handles synchronization and exception propagation.	9
	Add null checks for response handling The NewWindow method should handle potential null values in the response dictionary to prevent runtime exceptions. Add null checks and proper type casting. dotnet/src/webdriver/TargetLocator.cs [200-201] -Dictionary<string, object> result = (Dictionary<string, object>)response.Value!; -string newWindowHandle = result["handle"].ToString()!; +var result = response.Value as Dictionary<string, object> ?? throw new WebDriverException("Invalid response format"); +var handle = result["handle"] ?? throw new WebDriverException("Window handle not found in response"); +string newWindowHandle = handle.ToString() ?? throw new WebDriverException("Invalid window handle"); Apply this suggestion Suggestion importance[1-10]: 8 Why: The suggestion addresses potential runtime exceptions by adding proper null checks and error handling for the response dictionary, which is critical for application stability and error reporting.	8
Learned best practice	Add null validation check at the start of method to prevent potential NullReferenceException The GoToUrl(string url) method should validate the url parameter for null at the start of the method, similar to how it's done in GoToUrlAsync. Add an ArgumentNullException check to maintain consistency and prevent potential NullReferenceException. dotnet/src/webdriver/Navigator.cs [90-93] public void GoToUrl(string url) { + if (url == null) + { + throw new ArgumentNullException(nameof(url)); + } Task.Run(async delegate { await GoToUrlAsync(url).ConfigureAwait(false); }).GetAwaiter().GetResult(); } Apply this suggestion	6

[nvborisenko]

langword null?

[RenderMichael]

Will fix in a quick follow-up