fix(multipart-encoding): show encoding in snippet before file is uploaded

When the body is empty (no file selected), preserve the original
placeholder formdata params from the Postman request and apply the
selected encoding contentType to them. This ensures the code snippet
reflects the encoding selection immediately — before the user uploads
a file — since postman-code-generators emits `;type=<ct>` for FormParams
that have a contentType set.

Also wraps the Content-Type FormSelect in a div to push it onto its own
row below the property label.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sserrata

packages/docusaurus-theme-openapi-docs/src/theme/ApiExplorer/Body/FormBodyItem/index.tsx

@@ -98,16 +98,18 @@ export default function FormBodyItem({
       <>
         {label && <FormLabel label={label} required={required} />}
         {hasMultipleEncodings && (
-          <FormSelect
-            label="Content-Type"
-            options={encodingOptions}
-            value={selectedEncoding}
-            onChange={(e: React.ChangeEvent<HTMLSelectElement>) => {
-              const ct = e.target.value;
-              setSelectedEncoding(ct);
-              dispatch(setFieldEncoding({ field: id, contentType: ct }));
-            }}
-          />
+          <div style={{ marginTop: "0.5rem" }}>
+            <FormSelect
+              label="Content-Type"
+              options={encodingOptions}
+              value={selectedEncoding}
+              onChange={(e: React.ChangeEvent<HTMLSelectElement>) => {
+                const ct = e.target.value;
+                setSelectedEncoding(ct);
+                dispatch(setFieldEncoding({ field: id, contentType: ct }));
+              }}
+            />
+          </div>
         )}
         <FormFileUpload
           placeholder={schemaObject.description || id}

packages/docusaurus-theme-openapi-docs/src/theme/ApiExplorer/buildPostmanRequest.ts

@@ -303,6 +303,26 @@ function setBody(
   }
 
   if (body.type === "empty") {
+    // When the original request has formdata and encoding is declared, keep the
+    // placeholder params so the code snippet reflects the selected encoding even
+    // before the user has uploaded a file.
+    if (
+      clonedPostman.body?.mode === "formdata" &&
+      encoding &&
+      Object.keys(encoding).length > 0
+    ) {
+      const members: any[] =
+        (clonedPostman.body.formdata as any)?.members ?? [];
+      members.forEach((param: any) => {
+        const partContentType = encoding[param.key]?.contentType
+          ?.split(",")[0]
+          .trim();
+        if (partContentType) {
+          param.contentType = partContentType;
+        }
+      });
+      return;
+    }
     clonedPostman.body = undefined;
     return;
   }