[dotnet] [bidi] Support browser SetDownloadBehaviour command

[nvborisenko]

User description

https://w3c.github.io/webdriver-bidi/#command-browser-setDownloadBehavior

💥 What does this PR do?

Implements SetDownloadBehavior command.

💡 Additional Considerations

Not yet supported by browsers, but I verified locally whether we serialize command properly.

🔄 Types of changes

• New feature (non-breaking change which adds functionality and tests!)

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PR Type

Enhancement

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Description

• Implement WebDriver BiDi SetDownloadBehavior command

• Add support for allowed/denied download behaviors

• Include comprehensive test coverage for all scenarios

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Diagram Walkthrough

flowchart LR
  A["BrowserModule"] --> B["SetDownloadBehaviorCommand"]
  B --> C["DownloadBehavior Types"]
  C --> D["DownloadBehaviorAllowed"]
  C --> E["DownloadBehaviorDenied"]
  F["JSON Serialization"] --> B
  G["Tests"] --> A

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File Walkthrough

	Relevant files
Enhancement	BrowserModule.cs Add SetDownloadBehavior methods to BrowserModule                  dotnet/src/webdriver/BiDi/Browser/BrowserModule.cs Add three async methods for setting download behavior Support allowed behavior with destination folder Support allowed behavior with default settings Support denied behavior configuration +21/-0    SetDownloadBehaviorCommand.cs Create SetDownloadBehavior command infrastructure                dotnet/src/webdriver/BiDi/Browser/SetDownloadBehaviorCommand.cs Create new command class for SetDownloadBehavior Define polymorphic DownloadBehavior base class Implement DownloadBehaviorAllowed and DownloadBehaviorDenied types Add SetDownloadBehaviorOptions configuration class +43/-0
Configuration changes	BiDiJsonSerializerContext.cs Register command for JSON serialization                                    dotnet/src/webdriver/BiDi/Communication/Json/BiDiJsonSerializerContext.cs Register SetDownloadBehaviorCommand for JSON serialization +1/-0
Tests	BrowserTest.cs Add comprehensive SetDownloadBehavior tests                            dotnet/test/common/BiDi/Browser/BrowserTest.cs Add test for allowed download behavior with path Add test for default allowed download behavior Add test for denied download behavior Include browser ignore attributes for unsupported browsers +33/-0

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[qodo-code-review]

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[qodo-code-review]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
High-level	Re-evaluate the command parameter serialization The command parameter serialization for SetDownloadBehaviorCommand is incorrect. The implementation uses a nested, polymorphic object structure instead of the flat JSON structure with behavior and downloadPath fields required by the WebDriver BiDi specification. Examples: dotnet/src/webdriver/BiDi/Browser/SetDownloadBehaviorCommand.cs [29-38] internal sealed record SetDownloadBehaviorParameters([property: JsonIgnore(Condition = JsonIgnoreCondition.Never)] DownloadBehavior? DownloadBehavior, IEnumerable<UserContext>? UserContexts) : Parameters; [JsonPolymorphic(TypeDiscriminatorPropertyName = "type")] [JsonDerivedType(typeof(DownloadBehaviorAllowed), "allowed")] [JsonDerivedType(typeof(DownloadBehaviorDenied), "denied")] internal abstract record DownloadBehavior; internal sealed record DownloadBehaviorAllowed(string DestinationFolder) : DownloadBehavior; internal sealed record DownloadBehaviorDenied : DownloadBehavior; Solution Walkthrough: Before: // dotnet/src/webdriver/BiDi/Browser/SetDownloadBehaviorCommand.cs internal sealed record SetDownloadBehaviorParameters( DownloadBehavior? DownloadBehavior, IEnumerable<UserContext>? UserContexts) : Parameters; [JsonPolymorphic(TypeDiscriminatorPropertyName = "type")] [JsonDerivedType(typeof(DownloadBehaviorAllowed), "allowed")] [JsonDerivedType(typeof(DownloadBehaviorDenied), "denied")] internal abstract record DownloadBehavior; internal sealed record DownloadBehaviorAllowed(string DestinationFolder) : DownloadBehavior; internal sealed record DownloadBehaviorDenied : DownloadBehavior; After: // dotnet/src/webdriver/BiDi/Browser/SetDownloadBehaviorCommand.cs internal sealed record SetDownloadBehaviorParameters(string Behavior) : Parameters { [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] public string? DownloadPath { get; init; } [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] public IEnumerable<UserContext>? UserContexts { get; init; } } // dotnet/src/webdriver/BiDi/Browser/BrowserModule.cs public async Task<EmptyResult> SetDownloadBehaviorAllowedAsync(string destinationFolder, ...) { var @params = new SetDownloadBehaviorParameters("allow") { DownloadPath = destinationFolder, ... }; // ... } Suggestion importance[1-10]: 9 __ Why: The suggestion correctly identifies a critical serialization issue where the implemented JSON structure for SetDownloadBehaviorCommand parameters does not match the WebDriver BiDi specification, rendering the command incompatible.	High
Possible issue	Align download behavior models with spec Update the SetDownloadBehaviorParameters and DownloadBehaviorAllowed records to match the BiDi specification by making the behavior parameter non-nullable, renaming DestinationFolder to DownloadPath, making it optional, and adding correct JSON serialization attributes. dotnet/src/webdriver/BiDi/Browser/SetDownloadBehaviorCommand.cs [29-36] -internal sealed record SetDownloadBehaviorParameters([property: JsonIgnore(Condition = JsonIgnoreCondition.Never)] DownloadBehavior? DownloadBehavior, IEnumerable<UserContext>? UserContexts) : Parameters; +internal sealed record SetDownloadBehaviorParameters(DownloadBehavior Behavior, IEnumerable<UserContext>? UserContexts) : Parameters; [JsonPolymorphic(TypeDiscriminatorPropertyName = "type")] [JsonDerivedType(typeof(DownloadBehaviorAllowed), "allowed")] [JsonDerivedType(typeof(DownloadBehaviorDenied), "denied")] internal abstract record DownloadBehavior; -internal sealed record DownloadBehaviorAllowed(string DestinationFolder) : DownloadBehavior; +internal sealed record DownloadBehaviorAllowed( + [property: JsonPropertyName("downloadPath")] + [property: JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] + string? DownloadPath) : DownloadBehavior; Apply / Chat Suggestion importance[1-10]: 9 __ Why: The suggestion correctly identifies that the data models do not align with the BiDi specification, fixing nullability, property names, and optionality, which is critical for correct serialization and functionality.	High
	Update method calls for new models In BrowserModule.cs, update the SetDownloadBehaviorAllowedAsync overload to pass new DownloadBehaviorAllowed(null) instead of null for the behavior parameter to align with model changes and prevent a runtime error. dotnet/src/webdriver/BiDi/Browser/BrowserModule.cs [56-75] public async Task<EmptyResult> SetDownloadBehaviorAllowedAsync(string destinationFolder, SetDownloadBehaviorOptions? options = null) { var @params = new SetDownloadBehaviorParameters(new DownloadBehaviorAllowed(destinationFolder), options?.UserContexts); return await Broker.ExecuteCommandAsync<SetDownloadBehaviorCommand, EmptyResult>(new SetDownloadBehaviorCommand(@params), options).ConfigureAwait(false); } public async Task<EmptyResult> SetDownloadBehaviorAllowedAsync(SetDownloadBehaviorOptions? options = null) { - var @params = new SetDownloadBehaviorParameters(null, options?.UserContexts); + var @params = new SetDownloadBehaviorParameters(new DownloadBehaviorAllowed(null), options?.UserContexts); return await Broker.ExecuteCommandAsync<SetDownloadBehaviorCommand, EmptyResult>(new SetDownloadBehaviorCommand(@params), options).ConfigureAwait(false); } public async Task<EmptyResult> SetDownloadBehaviorDeniedAsync(SetDownloadBehaviorOptions? options = null) { var @params = new SetDownloadBehaviorParameters(new DownloadBehaviorDenied(), options?.UserContexts); return await Broker.ExecuteCommandAsync<SetDownloadBehaviorCommand, EmptyResult>(new SetDownloadBehaviorCommand(@params), options).ConfigureAwait(false); } Apply / Chat Suggestion importance[1-10]: 9 __ Why: This suggestion fixes a bug where a null value was passed for a required parameter, which would cause a runtime failure. The proposed change correctly instantiates the behavior object, ensuring the feature works as intended.	High
Learned best practice	Validate required string parameter Guard destinationFolder with null/empty/whitespace validation and throw a precise exception message before constructing parameters. dotnet/src/webdriver/BiDi/Browser/BrowserModule.cs [56-61] public async Task<EmptyResult> SetDownloadBehaviorAllowedAsync(string destinationFolder, SetDownloadBehaviorOptions? options = null) { + if (string.IsNullOrWhiteSpace(destinationFolder)) + { + throw new ArgumentException("destinationFolder is required and must be a non-empty path.", nameof(destinationFolder)); + } + var @params = new SetDownloadBehaviorParameters(new DownloadBehaviorAllowed(destinationFolder), options?.UserContexts); return await Broker.ExecuteCommandAsync<SetDownloadBehaviorCommand, EmptyResult>(new SetDownloadBehaviorCommand(@params), options).ConfigureAwait(false); } Apply / Chat Suggestion importance[1-10]: 6 __ Why: Relevant best practice - Validate inputs early to prevent null/invalid state; check required string parameters for null/empty before use.	Low
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