[dotnet] Annotate nullability on Firefox profile

[RenderMichael]

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Annotate nullability on Firefox profile

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 for FirefoxProfile and related classes.

• Refactored FirefoxProfile to use nullable reference types and improve code clarity.

• Added nullability checks and exceptions for better error handling.

• Updated utility methods to support nullable parameters and improve robustness.

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Changes walkthrough 📝

Relevant files

Enhancement

FirefoxProfile.cs Refactor and annotate nullability in FirefoxProfile            dotnet/src/webdriver/Firefox/FirefoxProfile.cs Enabled nullable reference types for the file. Refactored fields and properties to support nullability. Added nullability checks and exceptions for method parameters. Improved method signatures and internal logic for clarity and safety. +40/-43  FirefoxProfileManager.cs Add nullability and refactor FirefoxProfileManager              dotnet/src/webdriver/Firefox/FirefoxProfileManager.cs Enabled nullable reference types for the file. Refactored GetProfile method to handle nullable inputs. Simplified ExistingProfiles property with expression-bodied syntax. Used switch expressions for platform-specific logic. +13/-31  FileUtilities.cs Enhance FileUtilities with nullability support                      dotnet/src/webdriver/Internal/FileUtilities.cs Updated DeleteDirectory to accept nullable parameters. Added conditional compilation for GenerateRandomTempDirectoryName parameter attributes. Improved robustness of utility methods. +6/-2

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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 Reference The DirectoryInfo.Parent property access in DeleteExtensionsCache() assumes the parent directory exists. While marked with '!', this could still throw NullReferenceException if the extensions directory is at root level. string cacheFile = Path.Combine(ex.Parent!.FullName, "extensions.cache"); File Operations The DeleteLockFiles() method attempts to delete files without checking if they exist first. This could throw exceptions if the files don't exist. File.Delete(Path.Combine(profileDirectory, ".parentlock")); File.Delete(Path.Combine(profileDirectory, "parent.lock"));

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Add null check for required property Add null check for ProfileDirectory before using it in ToBase64String() to avoid potential NullReferenceException. The WriteToDisk() call may not have been made yet. dotnet/src/webdriver/Firefox/FirefoxProfile.cs [209] +if (string.IsNullOrEmpty(this.ProfileDirectory)) +{ + throw new InvalidOperationException("Profile directory not created. Call WriteToDisk() first."); +} string[] files = Directory.GetFiles(this.ProfileDirectory, "*.*", SearchOption.AllDirectories); Apply this suggestion Suggestion importance[1-10]: 8 Why: The suggestion addresses a critical null reference safety issue by adding a check for ProfileDirectory before using it in ToBase64String(). Without this check, the code could throw a NullReferenceException if WriteToDisk() hasn't been called.	8
	Validate required method parameter Add null check for profileDirectory parameter in DeleteLockFiles() to prevent potential NullReferenceException when combining paths. dotnet/src/webdriver/Firefox/FirefoxProfile.cs [236-240] private void DeleteLockFiles(string profileDirectory) { + ArgumentNullException.ThrowIfNull(profileDirectory); File.Delete(Path.Combine(profileDirectory, ".parentlock")); File.Delete(Path.Combine(profileDirectory, "parent.lock")); } Apply this suggestion Suggestion importance[1-10]: 7 Why: The suggestion improves code safety by adding parameter validation using ArgumentNullException.ThrowIfNull(), which aligns with the PR's focus on nullability and prevents potential runtime errors.	7
Learned best practice	Add null validation checks at the start of methods for required parameters marked as nullable to prevent NullReferenceExceptions The SetPreference methods should validate the name parameter at the start of the method since it's required but marked as nullable. Add ArgumentNullException checks using the recommended pattern. dotnet/src/webdriver/Firefox/FirefoxProfile.cs [127-129] public void SetPreference(string name, string value) { + ArgumentNullException.ThrowIfNull(name, nameof(name)); + ArgumentNullException.ThrowIfNull(value, nameof(value)); this.profilePreferences.SetPreference(name, value); } Apply this suggestion	6