[dotnet] Add nullability to FirefoxExtension

[RenderMichael]

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Description

Annotates nullability for FirefoxExtension

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

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Description

• Enhanced type safety by adding nullability annotations to FirefoxExtension class
• Improved null handling in XML and JSON manifest parsing methods
• Added explicit null checks in constructors and methods with appropriate exceptions
• Added XML documentation for null parameter exceptions
• Made fields readonly to improve immutability
• Simplified JSON parsing logic with null-conditional operators

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Changes walkthrough 📝

Relevant files

Enhancement

FirefoxExtension.cs Add nullability annotations and improve null handling        dotnet/src/webdriver/Firefox/FirefoxExtension.cs Added nullability annotations with #nullable enable Made fields readonly and added null checks in constructor Improved null handling in XML and JSON parsing methods Added exception documentation for null parameters +19/-24  FirefoxProfile.cs Add null parameter validation for AddExtension method        dotnet/src/webdriver/Firefox/FirefoxProfile.cs Added null check for extensionToInstall parameter Added exception documentation for null parameter +6/-0

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[qodo-merge-pro]

PR Reviewer Guide 🔍

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

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Null Reference The JSON parsing code assumes manifestObject is not null and directly accesses properties with '!'. This could throw NullReferenceException if the manifest.json file is malformed. var manifestObject = JsonNode.Parse(File.ReadAllText(manifestJsonPath)); if (manifestObject!["applications"]?["gecko"]?["id"] is { } idNode) { id = idNode.ToString().Trim(); } else { string addInName = manifestObject["name"]!.ToString().Replace(" ", ""); string addInVersion = manifestObject["version"]!.ToString(); id = string.Format(CultureInfo.InvariantCulture, "{0}@{1}", addInName, addInVersion);

[RenderMichael]

This already throws ArgumentNullException because of the Dictionary.Add just below

[qodo-merge-pro]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Add proper null checks when accessing JSON properties to prevent runtime exceptions Add null check for the manifestObject before accessing its properties to prevent potential NullReferenceException. dotnet/src/webdriver/Firefox/FirefoxExtension.cs [191-192] -string addInName = manifestObject["name"]!.ToString().Replace(" ", ""); -string addInVersion = manifestObject["version"]!.ToString(); +if (manifestObject?["name"] is null || manifestObject["version"] is null) +{ + throw new WebDriverException("Extension manifest.json must contain 'name' and 'version' fields"); +} +string addInName = manifestObject["name"].ToString().Replace(" ", ""); +string addInVersion = manifestObject["version"].ToString(); Apply this suggestion Suggestion importance[1-10]: 9 Why: Critical suggestion that prevents potential NullReferenceException when accessing required JSON properties. The improved error message also helps with debugging.	9
	Add parameter validation to prevent null reference exceptions Add null check for the profileDirectory parameter in the Install method to match the documented exception. dotnet/src/webdriver/Firefox/FirefoxExtension.cs [81-83] public void Install(string profileDirectory) { + if (profileDirectory is null) + { + throw new ArgumentNullException(nameof(profileDirectory)); + } DirectoryInfo info = new DirectoryInfo(profileDirectory); Apply this suggestion Suggestion importance[1-10]: 8 Why: The suggestion correctly identifies a missing null check that should match the documented exception. This is important for maintaining API contract and preventing runtime errors.	8
	Add validation for XML node existence before accessing its properties Add null check for descriptionNode before accessing its attributes to prevent potential NullReferenceException. dotnet/src/webdriver/Firefox/FirefoxExtension.cs [152-153] XmlNode? descriptionNode = rdfXmlDocument.SelectSingleNode("//RDF:Description", rdfNamespaceManager); -XmlAttribute? attribute = descriptionNode?.Attributes?["id", EmNamespaceUri]; +if (descriptionNode is null) +{ + throw new WebDriverException("Cannot locate RDF:Description node in extension manifest"); +} +XmlAttribute? attribute = descriptionNode.Attributes?["id", EmNamespaceUri]; Apply this suggestion Suggestion importance[1-10]: 7 Why: The suggestion adds important null validation for XML parsing, though the code already has some null safety through the nullable reference types and null-conditional operators.	7

[RenderMichael]

This is already unreachable with null using normal means, but this constructor is public-facing so we need the validation.