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Merged
rameel merged 2 commits into from
Aug 6, 2026
Merged

Defer HX-Trigger header serialization until response start #9

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48e9997
Defer HX-Trigger header serialization
rameel Jul 26, 2026
85c30d8
Unify deferred HTMX event headers
rameel Aug 6, 2026
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37 changes: 8 additions & 29 deletions src/Ramstack.HtmxToolkit/HtmxResponse.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,10 @@ namespace Ramstack.HtmxToolkit;
/// <summary>
/// Represents HTTP response to set htmx response headers.
/// </summary>
/// <remarks>
/// Like <see cref="HttpContext"/> and <see cref="HttpResponse"/> themselves, this type is not thread-safe.
/// Its members should not be called concurrently from multiple threads for the same request.
/// </remarks>
[DebuggerTypeProxy(typeof(HtmxResponseDebugView))]
public readonly struct HtmxResponse
{
Expand Down Expand Up @@ -211,7 +215,7 @@ public HtmxResponse TriggerEvent(string eventName, object detail, HtmxTriggerTim
return TriggerEventImpl(this, eventName, detail, timing);

static HtmxResponse TriggerEventImpl(HtmxResponse response, string eventName, object detail, HtmxTriggerTiming timing) =>
SetEvents(response, new Dictionary<string, object> { [eventName] = detail }, timing);
AddEvents(response, new Dictionary<string, object> { [eventName] = detail }, timing);
}

/// <summary>
Expand All @@ -224,7 +228,7 @@ static HtmxResponse TriggerEventImpl(HtmxResponse response, string eventName, ob
/// The current <see cref="HtmxResponse"/> instance.
/// </returns>
public HtmxResponse TriggerEvents(IReadOnlyDictionary<string, object> events, HtmxTriggerTiming timing = HtmxTriggerTiming.Receive) =>
SetEvents(this, events, timing);
AddEvents(this, events, timing);

/// <summary>
/// Sets the special HTTP status code <c>286</c> that is used to stop the polling.
Expand Down Expand Up @@ -256,34 +260,9 @@ private static HtmxResponse SetHeader(HtmxResponse response, string key, string
return response;
}

private static HtmxResponse SetEvents(HtmxResponse response, IReadOnlyDictionary<string, object> events, HtmxTriggerTiming timing)
private static HtmxResponse AddEvents(HtmxResponse response, IReadOnlyDictionary<string, object> events, HtmxTriggerTiming timing)
{
var key = timing switch
{
HtmxTriggerTiming.Receive => HtmxResponseHeaderNames.Trigger,
HtmxTriggerTiming.AfterSettle => HtmxResponseHeaderNames.TriggerAfterSettle,
_ => HtmxResponseHeaderNames.TriggerAfterSwap
};

if (response._response.Headers.TryGetValue(key, out var values))
{
var current = JsonSerializer.Deserialize<Dictionary<string, object>>(values.ToString())!;

if (events is Dictionary<string, object> dictionary)
{
foreach (var (k, v) in dictionary)
current.TryAdd(k, v);
}
else
{
foreach (var (k, v) in events)
current.TryAdd(k, v);
}

events = current;
}

response._response.Headers[key] = JsonSerializer.Serialize(events, JsonOptions.CamelCase);
PendingEvents.GetOrCreate(response._response).AddEvents(timing, events);
return response;
}

Expand Down
79 changes: 39 additions & 40 deletions src/Ramstack.HtmxToolkit/HtmxResponseHeaders.cs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,5 @@
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Text.Json;

using Microsoft.AspNetCore.Http;

using Ramstack.HtmxToolkit.Internal;
Expand All @@ -14,23 +12,23 @@ namespace Ramstack.HtmxToolkit;
[DebuggerTypeProxy(typeof(HtmxResponseHeadersDebugView))]
public sealed class HtmxResponseHeaders
{
private readonly IHeaderDictionary _headers;
private readonly HttpResponse _response;

/// <summary>
/// Initializes a new instance of the <see cref="HtmxResponseHeaders"/> structure.
/// </summary>
/// <param name="response">The HTTP response.</param>
internal HtmxResponseHeaders(HttpResponse response) =>
_headers = response.Headers;
_response = response;

/// <summary>
/// Gets or sets the <c>HX-Location</c> header to perform a client-side redirect without a full page reload.
/// </summary>
[MaybeNull]
public string Location
{
get => GetHeader(_headers, HtmxResponseHeaderNames.Location);
set => SetHeader(_headers, HtmxResponseHeaderNames.Location, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.Location);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Location, value);
}

/// <summary>
Expand All @@ -39,8 +37,8 @@ public string Location
[MaybeNull]
public string PushUrl
{
get => GetHeader(_headers, HtmxResponseHeaderNames.PushUrl);
set => SetHeader(_headers, HtmxResponseHeaderNames.PushUrl, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.PushUrl);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.PushUrl, value);
}

/// <summary>
Expand All @@ -49,17 +47,17 @@ public string PushUrl
[MaybeNull]
public string Redirect
{
get => GetHeader(_headers, HtmxResponseHeaderNames.Redirect);
set => SetHeader(_headers, HtmxResponseHeaderNames.Redirect, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.Redirect);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Redirect, value);
}

/// <summary>
/// Gets or sets the <c>HX-Refresh</c> header to perform a full page refresh.
/// </summary>
public bool Refresh
{
get => GetHeader(_headers, HtmxResponseHeaderNames.Refresh) == "true";
set => SetHeader(_headers, HtmxResponseHeaderNames.Refresh, value ? "true" : null);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.Refresh) == "true";
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Refresh, value ? "true" : null);
}

/// <summary>
Expand All @@ -69,8 +67,8 @@ public bool Refresh
[MaybeNull]
public string ReplaceUrl
{
get => GetHeader(_headers, HtmxResponseHeaderNames.ReplaceUrl);
set => SetHeader(_headers, HtmxResponseHeaderNames.ReplaceUrl, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.ReplaceUrl);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.ReplaceUrl, value);
}

/// <summary>
Expand All @@ -79,8 +77,8 @@ public string ReplaceUrl
[DisallowNull]
public HtmxSwap? Reswap
{
get => EnumHelper.ParseHtmxSwap(GetHeader(_headers, HtmxResponseHeaderNames.Reswap));
set => SetHeader(_headers, HtmxResponseHeaderNames.Reswap, value.GetValueOrDefault().GetSwapValue());
get => EnumHelper.ParseHtmxSwap(GetHeader(_response.Headers, HtmxResponseHeaderNames.Reswap));
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Reswap, value.GetValueOrDefault().GetSwapValue());
}

/// <summary>
Expand All @@ -89,8 +87,8 @@ public HtmxSwap? Reswap
[MaybeNull]
public string ReswapExpression
{
get => GetHeader(_headers, HtmxResponseHeaderNames.Reswap);
set => SetHeader(_headers, HtmxResponseHeaderNames.Reswap, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.Reswap);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Reswap, value);
}

/// <summary>
Expand All @@ -100,8 +98,8 @@ public string ReswapExpression
[MaybeNull]
public string Retarget
{
get => GetHeader(_headers, HtmxResponseHeaderNames.Retarget);
set => SetHeader(_headers, HtmxResponseHeaderNames.Retarget, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.Retarget);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Retarget, value);
}

/// <summary>
Expand All @@ -111,41 +109,53 @@ public string Retarget
[MaybeNull]
public string Reselect
{
get => GetHeader(_headers, HtmxResponseHeaderNames.Reselect);
set => SetHeader(_headers, HtmxResponseHeaderNames.Reselect, value);
get => GetHeader(_response.Headers, HtmxResponseHeaderNames.Reselect);
set => SetHeader(_response.Headers, HtmxResponseHeaderNames.Reselect, value);
}

/// <summary>
/// Gets or sets the <c>HX-Trigger</c> header, which specifies a dictionary of client-side events
/// to trigger after the server response is processed.
/// </summary>
/// <remarks>
/// Event values are accumulated for the current response and serialized into the header immediately
/// before the response starts.
/// </remarks>
[MaybeNull]
public IReadOnlyDictionary<string, object> Trigger
{
get => GetEvents(_headers, HtmxResponseHeaderNames.Trigger);
set => SetEvents(_headers, HtmxResponseHeaderNames.Trigger, value);
get => PendingEvents.TryGet(_response)?.GetEvents(HtmxTriggerTiming.Receive);
set => PendingEvents.GetOrCreate(_response).SetEvents(HtmxTriggerTiming.Receive, value);
}

/// <summary>
/// Gets or sets the <c>HX-Trigger-After-Settle</c> header, which specifies a dictionary of client-side events
/// to trigger after the htmx request has settled.
/// </summary>
/// <remarks>
/// Event values are accumulated for the current response and serialized into the header immediately
/// before the response starts.
/// </remarks>
[MaybeNull]
public IReadOnlyDictionary<string, object> TriggerAfterSettle
{
get => GetEvents(_headers, HtmxResponseHeaderNames.TriggerAfterSettle);
set => SetEvents(_headers, HtmxResponseHeaderNames.TriggerAfterSettle, value);
get => PendingEvents.TryGet(_response)?.GetEvents(HtmxTriggerTiming.AfterSettle);
set => PendingEvents.GetOrCreate(_response).SetEvents(HtmxTriggerTiming.AfterSettle, value);
}

/// <summary>
/// Gets or sets the <c>HX-Trigger-After-Swap</c> header, which specifies a dictionary of client-side events
/// to trigger after the response content has been swapped into the DOM.
/// </summary>
/// <remarks>
/// Event values are accumulated for the current response and serialized into the header immediately
/// before the response starts.
/// </remarks>
[MaybeNull]
public IReadOnlyDictionary<string, object> TriggerAfterSwap
{
get => GetEvents(_headers, HtmxResponseHeaderNames.TriggerAfterSwap);
set => SetEvents(_headers, HtmxResponseHeaderNames.TriggerAfterSwap, value);
get => PendingEvents.TryGet(_response)?.GetEvents(HtmxTriggerTiming.AfterSwap);
set => PendingEvents.GetOrCreate(_response).SetEvents(HtmxTriggerTiming.AfterSwap, value);
}

private static string? GetHeader(IHeaderDictionary headers, string key)
Expand All @@ -160,23 +170,12 @@ private static void SetHeader(IHeaderDictionary headers, string key, string? val
headers[key] = value;
}

private static Dictionary<string, object>? GetEvents(IHeaderDictionary headers, string key)
{
if (headers.TryGetValue(key, out var values))
return JsonSerializer.Deserialize<Dictionary<string, object>>(values.ToString());

return null;
}

private static void SetEvents(IHeaderDictionary headers, string key, IReadOnlyDictionary<string, object> events) =>
headers[key] = JsonSerializer.Serialize(events, JsonOptions.CamelCase);

#region Inner type: HtmxResponseHeadersDebugView

private sealed class HtmxResponseHeadersDebugView(HtmxResponseHeaders headers)
{
[DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
public KeyValuePair<string, string>[] Items => DebugHelpers.GetHeaders(headers._headers);
public KeyValuePair<string, string>[] Items => DebugHelpers.GetHeaders(headers._response.Headers);
}

#endregion
Expand Down
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