Add support for multipart/data uploads in swagger

src/FrameProcessor/Program.cs

@@ -5,6 +5,7 @@ using FrameProcessor.Middleware;
 using FrameProcessor.Mqtt;
 using FrameProcessor.Storage;
 using FrameProcessor.UrlFetch;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
 using Microsoft.Extensions.Options;
 using Microsoft.OpenApi;
 using Serilog;
@@ -50,6 +51,68 @@ builder.Services.AddOpenApi(options =>
         ];
         return Task.CompletedTask;
     });
+
+    // Microsoft.AspNetCore.OpenApi (10.0) does not emit a multipart/form-data
+    // request body for [FromForm] IFormFile parameters on MVC controllers, so
+    // Swagger UI renders no upload widget. Synthesize one here for any operation
+    // whose action takes form-bound parameters.
+    options.AddOperationTransformer((operation, context, _) =>
+    {
+        var formParams = context.Description.ParameterDescriptions
+            .Where(p => p.Source == BindingSource.FormFile || p.Source == BindingSource.Form)
+            .ToList();
+
+        if (formParams.Count == 0)
+        {
+            return Task.CompletedTask;
+        }
+
+        var properties = new Dictionary<string, IOpenApiSchema>();
+        var required = new HashSet<string>();
+
+        foreach (var p in formParams)
+        {
+            var isFile = p.Source == BindingSource.FormFile
+                || typeof(IFormFile).IsAssignableFrom(p.ModelMetadata?.ModelType);
+
+            properties[p.Name] = new OpenApiSchema
+            {
+                Type = JsonSchemaType.String,
+                Format = isFile ? "binary" : null,
+            };
+
+            if (p.IsRequired)
+            {
+                required.Add(p.Name);
+            }
+        }
+
+        operation.RequestBody = new OpenApiRequestBody
+        {
+            Required = true,
+            Content = new Dictionary<string, OpenApiMediaType>
+            {
+                ["multipart/form-data"] = new OpenApiMediaType
+                {
+                    Schema = new OpenApiSchema
+                    {
+                        Type = JsonSchemaType.Object,
+                        Properties = properties,
+                        Required = required,
+                    },
+                },
+            },
+        };
+
+        if (operation.Parameters is { Count: > 0 })
+        {
+            var formNames = formParams.Select(p => p.Name).ToHashSet(StringComparer.OrdinalIgnoreCase);
+            var filtered = operation.Parameters.Where(p => p.Name is null || !formNames.Contains(p.Name)).ToList();
+            operation.Parameters = filtered.Count > 0 ? filtered : null;
+        }
+
+        return Task.CompletedTask;
+    });
 });
 
 builder.Services.AddOptions<MqttOptions>()