[dotnet] Make FirefoxProfile AOT-safe

[RenderMichael]

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Description

This PR hand-rolls parsing of the webdriver_prefs.json file, instead of parsing into a Dictionary<string, object>

This PR is a lot easier to read with whitespace disabled.

Motivation and Context

An open-typed object dictionary is inherently AOT-unsafe. In this scenario, we know the expected structure of the JSON, so we can manually parse the values.

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

• Refactored JSON parsing in FirefoxProfile to use JsonObject instead of Dictionary<string, object>, enhancing AOT safety.
• Updated Preferences class to handle preferences using JsonNode, improving type safety and performance.
• Added nullability annotations to improve code quality and prevent null reference exceptions.
• Enhanced exception handling for preference setting and JSON parsing.

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Changes walkthrough 📝

Relevant files

Enhancement

FirefoxProfile.cs Refactor JSON Parsing to Use JsonObject for AOT Safety      dotnet/src/webdriver/Firefox/FirefoxProfile.cs Replaced Dictionary with JsonObject for JSON parsing. Removed custom JSON serialization options. Improved exception handling for JSON parsing. +6/-12    Preferences.cs Update Preferences Handling with JsonNode and Nullability dotnet/src/webdriver/Firefox/Preferences.cs Changed preference storage to use JsonNode. Updated SetPreferenceValue to handle JsonNode. Added nullability annotations. Improved exception handling for preference setting. +40/-26

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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 Handling The code assumes JsonNode values will be JsonValue and can be converted to primitive types. Need to validate the error handling for null or invalid JSON node types. Error Handling The null coalescing operator for JsonObject casting should include more descriptive error message about the expected JSON structure. Type Safety The preference value parsing logic could be more robust by handling additional numeric types like double/float that may appear in the JSON.

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PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Score
Possible issue	Add input validation to prevent null reference exceptions when parsing JSON data Add null check for defaultPreferences string before parsing to prevent potential NullReferenceException. dotnet/src/webdriver/Firefox/FirefoxProfile.cs [303-304] string defaultPreferences = reader.ReadToEnd(); +if (string.IsNullOrEmpty(defaultPreferences)) + throw new WebDriverException("webdriver_prefs.json was empty"); JsonObject deserializedPreferences = JsonNode.Parse(defaultPreferences) as JsonObject Apply this suggestion Suggestion importance[1-10]: 8 Why: The suggestion adds important null validation for JSON data, preventing potential runtime crashes. This is a critical defensive programming practice for handling external data.	8
Possible bug	✅ Add parameter validation to prevent null reference exceptions Suggestion Impact: The commit added a null check for the key parameter in the SetPreference method, which aligns with the suggestion to prevent null reference exceptions. code diff: internal void SetPreference(string key, string value) { - this.SetPreferenceValue(key, value); + if (key is null) + { + throw new ArgumentNullException(nameof(key)); + } Add null check for key parameter in SetPreferenceValue method to prevent potential issues with null keys. dotnet/src/webdriver/Firefox/Preferences.cs [166-168] private void SetPreferenceValue(string key, JsonNode? value) { + if (key == null) + throw new ArgumentNullException(nameof(key)); if (!this.IsSettablePreference(key)) Apply this suggestion Suggestion importance[1-10]: 7 Why: Adding null validation for method parameters is a crucial defensive programming practice that prevents potential null reference exceptions and improves code reliability.	7

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[RenderMichael]

Support for floating-point preferences has been added and the error message has been changed to reflect that.

This PR is ready for another look!

[nvborisenko]

Thank you, @RenderMichael !