fix: return empty/null on 204 No Content and empty response bodies

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.2.1] - 2026-05-13
+
+### Fixed
+
+- `GetComputersAsync`, `GetProductsAsync`, `GetWebhooksAsync`, and `GetWebhookDeliveriesAsync` no longer throw `System.Text.Json.JsonException` ("The input does not contain any JSON tokens") when the server returns HTTP 204 No Content or HTTP 200 with an empty body. They now return an empty sequence.
+- The same empty-body guard was applied to the single-item `GetLicenseAsync`, `GetReceiptAsync`, `GetProductAsync`, `GetComputerAsync`, and `GetWebhookAsync` methods, which now return `null` consistently on 204 or 200-with-empty-body responses.
+- Deserialization is centralized in new `ReadJsonOrDefaultAsync<T>` / `ReadJsonOrEmptyAsync<T>` helpers so future endpoints inherit the guard automatically.
+
 ## [1.2.0] - 2025-12-17
 
 ### Added

LicenseManagement.Client.csproj

@@ -8,7 +8,7 @@
 
     <!-- NuGet Package Properties -->
     <PackageId>LicenseManagement.Client</PackageId>
-    <Version>1.2.0</Version>
+    <Version>1.2.1</Version>
     <Authors>Hymma</Authors>
     <Company>Hymma</Company>
     <Product>License Management Client SDK</Product>
@@ -27,6 +27,14 @@
     <None Include="README.md" Pack="true" PackagePath="" />
   </ItemGroup>
 
+  <!-- Test project lives under Tests/ — exclude from the package's implicit globs. -->
+  <ItemGroup>
+    <Compile Remove="Tests\**" />
+    <Content Remove="Tests\**" />
+    <EmbeddedResource Remove="Tests\**" />
+    <None Remove="Tests\**" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Http" Version="8.0.0" />

LicenseManagementClient.cs

@@ -51,12 +51,8 @@ private void ConfigureHttpClient()
     public async Task<License?> GetLicenseAsync(string productId, string computerId, CancellationToken cancellationToken = default)
     {
         var response = await _httpClient.GetAsync($"license?product={Uri.EscapeDataString(productId)}&computer={Uri.EscapeDataString(computerId)}", cancellationToken);
-
-        if (response.StatusCode == HttpStatusCode.NoContent)
-            return null;
-
         await EnsureSuccessAsync(response);
-        return await response.Content.ReadFromJsonAsync<License>(JsonOptions, cancellationToken);
+        return await ReadJsonOrDefaultAsync<License>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -91,12 +87,8 @@ public async Task UpdateLicenseAsync(UpdateLicenseRequest request, CancellationT
     public async Task<Receipt?> GetReceiptAsync(string code, CancellationToken cancellationToken = default)
     {
         var response = await _httpClient.GetAsync($"receipt?code={Uri.EscapeDataString(code)}", cancellationToken);
-
-        if (response.StatusCode == HttpStatusCode.NoContent)
-            return null;
-
         await EnsureSuccessAsync(response);
-        return await response.Content.ReadFromJsonAsync<Receipt>(JsonOptions, cancellationToken);
+        return await ReadJsonOrDefaultAsync<Receipt>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -184,12 +176,8 @@ await CreateReceiptAsync(new CreateReceiptRequest
     public async Task<IEnumerable<Receipt>> GetReceiptsAsync(string buyerEmail, string productId, CancellationToken cancellationToken = default)
     {
         var response = await _httpClient.GetAsync($"receipt/all?buyerEmail={Uri.EscapeDataString(buyerEmail)}&product={Uri.EscapeDataString(productId)}", cancellationToken);
-
-        if (response.StatusCode == HttpStatusCode.NoContent)
-            return Enumerable.Empty<Receipt>();
-
         await EnsureSuccessAsync(response);
-        return (await response.Content.ReadFromJsonAsync<IEnumerable<Receipt>>(JsonOptions, cancellationToken)) ?? Enumerable.Empty<Receipt>();
+        return await ReadJsonOrEmptyAsync<Receipt>(response, cancellationToken);
     }
 
     #endregion
@@ -200,20 +188,16 @@ public async Task<IEnumerable<Receipt>> GetReceiptsAsync(string buyerEmail, stri
     public async Task<Product?> GetProductAsync(string productId, CancellationToken cancellationToken = default)
     {
         var response = await _httpClient.GetAsync($"product?product={Uri.EscapeDataString(productId)}", cancellationToken);
-
-        if (response.StatusCode == HttpStatusCode.NoContent)
-            return null;
-
         await EnsureSuccessAsync(response);
-        return await response.Content.ReadFromJsonAsync<Product>(JsonOptions, cancellationToken);
+        return await ReadJsonOrDefaultAsync<Product>(response, cancellationToken);
     }
 
     /// <inheritdoc />
     public async Task<IEnumerable<Product>> GetProductsAsync(CancellationToken cancellationToken = default)
     {
         var response = await _httpClient.GetAsync("product/all", cancellationToken);
         await EnsureSuccessAsync(response);
-        return (await response.Content.ReadFromJsonAsync<IEnumerable<Product>>(JsonOptions, cancellationToken))!;
+        return await ReadJsonOrEmptyAsync<Product>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -241,12 +225,8 @@ public async Task<Product> CreateProductAsync(CreateProductRequest request, Canc
     public async Task<Computer?> GetComputerAsync(string macAddress, CancellationToken cancellationToken = default)
     {
         var response = await _httpClient.GetAsync($"computer?macAddress={Uri.EscapeDataString(macAddress)}", cancellationToken);
-
-        if (response.StatusCode == HttpStatusCode.NoContent)
-            return null;
-
         await EnsureSuccessAsync(response);
-        return await response.Content.ReadFromJsonAsync<Computer>(JsonOptions, cancellationToken);
+        return await ReadJsonOrDefaultAsync<Computer>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -271,7 +251,7 @@ public async Task<IEnumerable<Computer>> GetComputersAsync(string receiptCode, C
     {
         var response = await _httpClient.GetAsync($"computer/all?receiptCode={Uri.EscapeDataString(receiptCode)}", cancellationToken);
         await EnsureSuccessAsync(response);
-        return (await response.Content.ReadFromJsonAsync<IEnumerable<Computer>>(JsonOptions, cancellationToken))!;
+        return await ReadJsonOrEmptyAsync<Computer>(response, cancellationToken);
     }
 
     #endregion
@@ -299,7 +279,7 @@ public async Task<IEnumerable<Webhook>> GetWebhooksAsync(CancellationToken cance
     {
         var response = await _httpClient.GetAsync("webhook", cancellationToken);
         await EnsureSuccessAsync(response);
-        return (await response.Content.ReadFromJsonAsync<IEnumerable<Webhook>>(JsonOptions, cancellationToken))!;
+        return await ReadJsonOrEmptyAsync<Webhook>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -311,7 +291,7 @@ public async Task<IEnumerable<Webhook>> GetWebhooksAsync(CancellationToken cance
             return null;
 
         await EnsureSuccessAsync(response);
-        return await response.Content.ReadFromJsonAsync<Webhook>(JsonOptions, cancellationToken);
+        return await ReadJsonOrDefaultAsync<Webhook>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -369,7 +349,7 @@ public async Task<IEnumerable<WebhookDelivery>> GetWebhookDeliveriesAsync(string
 
         var response = await _httpClient.GetAsync(url, cancellationToken);
         await EnsureSuccessAsync(response);
-        return (await response.Content.ReadFromJsonAsync<IEnumerable<WebhookDelivery>>(JsonOptions, cancellationToken))!;
+        return await ReadJsonOrEmptyAsync<WebhookDelivery>(response, cancellationToken);
     }
 
     /// <inheritdoc />
@@ -430,6 +410,30 @@ public async Task TestWebhookAsync(string webhookId, CancellationToken cancellat
 
     #region Helpers
 
+    /// <summary>
+    /// Deserializes a JSON response body, returning default(T) when the response is 204 No Content
+    /// or has an empty body. Guards against System.Text.Json throwing on empty input.
+    /// </summary>
+    private static async Task<T?> ReadJsonOrDefaultAsync<T>(HttpResponseMessage response, CancellationToken cancellationToken)
+    {
+        if (response.StatusCode == HttpStatusCode.NoContent || response.Content.Headers.ContentLength == 0)
+            return default;
+
+        return await response.Content.ReadFromJsonAsync<T>(JsonOptions, cancellationToken);
+    }
+
+    /// <summary>
+    /// Deserializes a JSON array response body, returning an empty sequence when the response is
+    /// 204 No Content, has an empty body, or deserializes to null.
+    /// </summary>
+    private static async Task<IEnumerable<T>> ReadJsonOrEmptyAsync<T>(HttpResponseMessage response, CancellationToken cancellationToken)
+    {
+        if (response.StatusCode == HttpStatusCode.NoContent || response.Content.Headers.ContentLength == 0)
+            return Enumerable.Empty<T>();
+
+        return (await response.Content.ReadFromJsonAsync<IEnumerable<T>>(JsonOptions, cancellationToken)) ?? Enumerable.Empty<T>();
+    }
+
     /// <summary>
     /// Sends a PATCH request with JSON body (cross-platform compatible).
     /// </summary>

Tests/LicenseManagement.Client.Tests/EmptyResponseTests.cs

@@ -0,0 +1,177 @@
+using System.Net;
+using System.Text;
+using LicenseManagement.Client;
+using LicenseManagement.Client.Models;
+using Microsoft.Extensions.Options;
+
+namespace LicenseManagement.Client.Tests;
+
+/// <summary>
+/// Regression tests for the bug where Get* collection methods threw
+/// System.Text.Json.JsonException on HTTP 204 No Content or 200 with empty body.
+/// </summary>
+public class EmptyResponseTests
+{
+    private static LicenseManagementClient CreateClient(Func<HttpRequestMessage, HttpResponseMessage> responder)
+    {
+        var handler = new StubHandler(responder);
+        var httpClient = new HttpClient(handler);
+        var options = Options.Create(new LicenseManagementClientOptions
+        {
+            BaseUrl = "https://example.test",
+            ApiKey = "test-key",
+            TimeoutSeconds = 30
+        });
+        return new LicenseManagementClient(httpClient, options);
+    }
+
+    private static HttpResponseMessage NoContent() => new(HttpStatusCode.NoContent);
+
+    private static HttpResponseMessage OkEmpty()
+    {
+        var response = new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = new StringContent(string.Empty, Encoding.UTF8, "application/json")
+        };
+        return response;
+    }
+
+    [Fact]
+    public async Task GetComputersAsync_Returns_Empty_On_204_NoContent()
+    {
+        var client = CreateClient(_ => NoContent());
+
+        var result = await client.GetComputersAsync("RCP_123");
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetComputersAsync_Returns_Empty_On_200_With_Empty_Body()
+    {
+        var client = CreateClient(_ => OkEmpty());
+
+        var result = await client.GetComputersAsync("RCP_123");
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetComputersAsync_Returns_Items_On_200_With_Json_Array()
+    {
+        var json = "[{\"id\":\"PC_1\",\"macAddress\":\"AA:BB:CC:DD:EE:FF\",\"name\":\"Dev box\"}]";
+        var client = CreateClient(_ => new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = new StringContent(json, Encoding.UTF8, "application/json")
+        });
+
+        var result = (await client.GetComputersAsync("RCP_123")).ToList();
+
+        Assert.Single(result);
+        Assert.Equal("PC_1", result[0].Id);
+    }
+
+    [Fact]
+    public async Task GetProductsAsync_Returns_Empty_On_204_NoContent()
+    {
+        var client = CreateClient(_ => NoContent());
+
+        var result = await client.GetProductsAsync();
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetProductsAsync_Returns_Empty_On_200_With_Empty_Body()
+    {
+        var client = CreateClient(_ => OkEmpty());
+
+        var result = await client.GetProductsAsync();
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetReceiptsAsync_Returns_Empty_On_204_NoContent()
+    {
+        var client = CreateClient(_ => NoContent());
+
+        var result = await client.GetReceiptsAsync("buyer@example.com", "PRD_1");
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetReceiptsAsync_Returns_Empty_On_200_With_Empty_Body()
+    {
+        var client = CreateClient(_ => OkEmpty());
+
+        var result = await client.GetReceiptsAsync("buyer@example.com", "PRD_1");
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetWebhooksAsync_Returns_Empty_On_204_NoContent()
+    {
+        var client = CreateClient(_ => NoContent());
+
+        var result = await client.GetWebhooksAsync();
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetWebhooksAsync_Returns_Empty_On_200_With_Empty_Body()
+    {
+        var client = CreateClient(_ => OkEmpty());
+
+        var result = await client.GetWebhooksAsync();
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetWebhookDeliveriesAsync_Returns_Empty_On_204_NoContent()
+    {
+        var client = CreateClient(_ => NoContent());
+
+        var result = await client.GetWebhookDeliveriesAsync("WH_1");
+
+        Assert.NotNull(result);
+        Assert.Empty(result);
+    }
+
+    [Fact]
+    public async Task GetComputerAsync_Returns_Null_On_200_With_Empty_Body()
+    {
+        var client = CreateClient(_ => OkEmpty());
+
+        var result = await client.GetComputerAsync("AA:BB:CC:DD:EE:FF");
+
+        Assert.Null(result);
+    }
+
+    private sealed class StubHandler : HttpMessageHandler
+    {
+        private readonly Func<HttpRequestMessage, HttpResponseMessage> _responder;
+
+        public StubHandler(Func<HttpRequestMessage, HttpResponseMessage> responder)
+        {
+            _responder = responder;
+        }
+
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(_responder(request));
+        }
+    }
+}

Tests/LicenseManagement.Client.Tests/LicenseManagement.Client.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\LicenseManagement.Client.csproj" />
+  </ItemGroup>
+
+</Project>