[go_router] Add `encoder`,`decoder` and `compare` parameters to `TypedQueryParameter` by ValentinVignal · Pull Request #11067 · flutter/packages

ValentinVignal · 2026-02-19T05:54:54Z

Part of

[go_router_builder] Allow the user to specify a type converter of the parameters flutter#112152
[go_router_builder] Custom type conversion for parameters flutter#110781

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This pull request enhances TypedQueryParameter by adding encoder, decoder, and compare parameters, allowing for more flexible handling of query parameters in type-safe routes. The changes are well-implemented and include corresponding updates to the changelog, pubspec, and tests. I have one suggestion to improve the clarity of the documentation for the new compare parameter to prevent potential misuse.

gemini-code-assist · 2026-02-19T05:55:55Z

packages/go_router/lib/src/route_data.dart

+  /// A function that compares two parameter values for equality.
+  ///
+  /// Returns `true` if the values are different and `false` if they are the
+  /// same. This is used to determine whether a parameter should be included in
+  /// the URI when it has a default value.


The documentation for the compare function is a bit confusing. The first sentence says it's for equality comparison, but the following sentence states it returns true if the values are different. This is counter-intuitive for a function that is described as comparing for equality.

To avoid confusion for developers using this API, I suggest rephrasing the documentation to be more direct about its purpose. For example, you could describe it as an inequality check.

Suggested change

/// A function that compares two parameter values for equality.

///

/// Returns `true` if the values are different and `false` if they are the

/// same. This is used to determine whether a parameter should be included in

/// the URI when it has a default value.

/// A function that compares two parameter values for inequality.

///

/// Returns `true` if the values are considered different, and `false` if they

/// are the same. This is used to determine whether a parameter should be

/// included in the URI when it has a default value.

ValentinVignal · 2026-02-19T06:00:19Z

go_router_builder PR: #11068

ValentinVignal · 2026-02-19T06:04:14Z

The analyzer is failing because of go_router_builder example

Got dependencies in `./example`.
Running command: "dart analyze --fatal-infos" in /b/s/w/ir/x/w/packages/packages/go_router_builder
Analyzing go_router_builder...

warning - example/lib/typed_query_parameter_example.dart:30:5 - The type argument(s) of the constructor 'TypedQueryParameter' can't be inferred. Use explicit type argument(s) for 'TypedQueryParameter'. - inference_failure_on_instance_creation
warning - example/lib/typed_query_parameter_example.dart:31:5 - The type argument(s) of the constructor 'TypedQueryParameter' can't be inferred. Use explicit type argument(s) for 'TypedQueryParameter'. - inference_failure_on_instance_creation
warning - example/lib/typed_query_parameter_example.dart:33:5 - The type argument(s) of the constructor 'TypedQueryParameter' can't be inferred. Use explicit type argument(s) for 'TypedQueryParameter'. - inference_failure_on_instance_creation
warning - test_inputs/typed_query_parameter.dart:13:5 - The type argument(s) of the constructor 'TypedQueryParameter' can't be inferred. Use explicit type argument(s) for 'TypedQueryParameter'. - inference_failure_on_instance_creation
warning - test_inputs/typed_query_parameter.dart:14:5 - The type argument(s) of the constructor 'TypedQueryParameter' can't be inferred. Use explicit type argument(s) for 'TypedQueryParameter'. - inference_failure_on_instance_creation

Now, TypedQueryParameter takes a generic type. I've updated those in the go_router_builder PR: #11068.
Should I update them in this PR?

chunhtai · 2026-02-19T22:37:58Z

packages/go_router/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 17.2.0
+
+- Adds `encoder`, `decoder` and `compare` parameters to `TypedQueryParameter` annotation for custom encoding, decoding and comparison of query parameters in `TypedGoRoute` constructors.


go_router has migrated to batch release, now we should add a new entry in pending_changelogs folder. the ci also hinted this.

Oh okay, I changed it in Use batch release, let me know if that's correct

chunhtai · 2026-02-19T22:42:44Z

packages/go_router/lib/src/route_data.dart

+  /// The returned string is escaped to be URL-safe. For example, a parameter
+  /// value of `'field with space'` will generate a query parameter value of
+  /// `'field+with+space'`.
+  final String? Function(T?)? encoder;


we should typedef this. also what does returning null does here? and in what case will null to be feed into this. we should document these behavior in the typedef

Good point, I made the parameter non-nullable in Better documentation

chunhtai · 2026-02-19T22:43:27Z

packages/go_router/lib/src/route_data.dart

+  /// A function that converts a string from the URI to a parameter value.
+  final T? Function(String?)? decoder;
+
+  /// A function that compares two parameter values for equality.


can you talk a bit more why this is needed?

Let me know if that's good enough or not Better documentation

chunhtai · 2026-02-23T23:50:45Z

packages/go_router/lib/src/route_data.dart

+/// For example, a parameter value of `'field with space'` will generate a query
+/// parameter value of `'field+with+space'`.
+///
+/// If the function returns `null`, the parameter will be treated as if it were


what is the use case for this?

I don't think there is really a "use-case"

A typical encoder (with a nullable type) would be something like:

String? encoder(T? value) { // Nullable T here. if (value == null) return null; // If there is no parameter in the route, we don't want any parameter in the URL // Encoder logic for non-null T. }

Maybe the phrasing is not the best?

chunhtai · 2026-02-23T23:52:02Z

packages/go_router/lib/src/route_data.dart

+/// The [value] parameter contains the encoded string from the URI, or `null`
+/// if the parameter is absent from the URI.
+///
+/// Return `null` to indicate the parameter was not provided. In this case,


Same, can you talk a bit about the use case here?

I don't think there is a use case per say.

Here, the most common use case would be to return null if String? value is null:

T? myDecoder(String? value) { if (value == null) return null; // More logic. }

chunhtai · 2026-02-23T23:53:13Z

packages/go_router/lib/src/route_data.dart

+///
+/// Converts an encoded string from the URI into a parameter value of type `T`.
+///
+/// The [value] parameter contains the encoded string from the URI, or `null`


in that case shouldn't this be handled by setting the default value in GoRouteData?

yes, if there is a default value in GoRouteData being set and the decoder returns true, it will use the default value of GoRouteData :)

chunhtai · 2026-02-23T23:54:21Z

packages/go_router/lib/src/route_data.dart

+  ///
+  /// Used to decide whether to include a parameter in the URI when a default
+  /// value exists. If the parameter equals its default value, it is omitted
+  /// from the URI; otherwise, it is included.


should mention this must be provided if the T is not primative type and has default value

Good point, I added it in Add optionalTypeArgs, assert, and better documentation

ValentinVignal requested a review from chunhtai as a code owner February 19, 2026 05:54

ValentinVignal changed the title ~~[go_router] Add encoder,decoder and compare parameters to `TypedQueryParameter~~ [go_router] Add encoder,decoder and compare parameters to TypedQueryParameter Feb 19, 2026

github-actions bot added p: go_router triage-framework Should be looked at in framework triage labels Feb 19, 2026

gemini-code-assist bot reviewed Feb 19, 2026

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ValentinVignal mentioned this pull request Feb 19, 2026

[go_router_builder] Support custom types #11068

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chunhtai reviewed Feb 19, 2026

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ValentinVignal added 4 commits February 23, 2026 15:52

Support custom types

da840ce

Better doc

9054ebe

Use batch release

b9e1129

Better documentation

624a61b

ValentinVignal force-pushed the go-router/support-custom-types branch from 3e95760 to 624a61b Compare February 23, 2026 09:30

ValentinVignal requested a review from chunhtai February 23, 2026 09:43

chunhtai reviewed Feb 23, 2026

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Add optionalTypeArgs, assert, and better documenation

0af5c25

ValentinVignal requested a review from chunhtai February 24, 2026 05:58

Fix linter

88ce580

		@@ -1,3 +1,7 @@
		## 17.2.0

		- Adds `encoder`, `decoder` and `compare` parameters to `TypedQueryParameter` annotation for custom encoding, decoding and comparison of query parameters in `TypedGoRoute` constructors.

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ValentinVignal commented Feb 19, 2026

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ValentinVignal Feb 24, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ValentinVignal Feb 24, 2026 •

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