Fix (android): show payload preview for FormData and one-shot uploads in DevTools (#55764)

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/modules/network/NetworkEventUtil.kt

@@ -260,15 +260,16 @@ internal object NetworkEventUtil {
     val body = (requestBody as? ProgressRequestBody)?.innerBody() ?: requestBody
 
     if (body.isOneShot()) {
-      // Fallback - body cannot be read twice
-      return "[Preview unavailable]"
+      // Reading would drain the underlying stream and break the real upload,
+      // so fall back to a placeholder that includes the byte count when known
+      return binaryPartLabel(body)
     }
 
     // MultipartBody does not propagate isOneShot() from its parts, so check each
     // part explicitly. Reading a one-shot part here would drain the underlying
     // stream and cause the real request to fail.
     if (body is MultipartBody && body.parts().any { it.body().isOneShot() }) {
-      return "[Preview unavailable]"
+      return previewMultipartWithBinaryParts(body)
     }
 
     return try {
@@ -285,4 +286,53 @@ internal object NetworkEventUtil {
       "[Preview unavailable]"
     }
   }
+
+  private fun previewMultipartWithBinaryParts(body: MultipartBody): String {
+    val boundary = body.boundary()
+    val out = StringBuilder()
+
+    for (part in body.parts()) {
+      out.append("--").append(boundary).append("\r\n")
+
+      part.headers()?.let { headers ->
+        for (i in 0 until headers.size()) {
+          out.append(headers.name(i)).append(": ").append(headers.value(i)).append("\r\n")
+        }
+      }
+      val partBody = part.body()
+      partBody.contentType()?.let { out.append("Content-Type: ").append(it).append("\r\n") }
+      out.append("\r\n")
+
+      if (partBody.isOneShot()) {
+        out.append(binaryPartLabel(partBody))
+      } else {
+        try {
+          val partBuffer = Buffer()
+          partBody.writeTo(partBuffer)
+          out.append(partBuffer.readUtf8())
+        } catch (e: IOException) {
+          out.append("[Preview unavailable]")
+        }
+      }
+      out.append("\r\n")
+    }
+    out.append("--").append(boundary).append("--\r\n")
+
+    return if (out.length <= MAX_BODY_PREVIEW_SIZE) {
+      out.toString()
+    } else {
+      out.substring(0, MAX_BODY_PREVIEW_SIZE) + "... (truncated, ${out.length} bytes total)"
+    }
+  }
+
+  /** Placeholder for a one-shot body, including the byte count when known. */
+  private fun binaryPartLabel(body: RequestBody): String {
+    val length =
+        try {
+          body.contentLength()
+        } catch (e: IOException) {
+          -1L
+        }
+    return if (length >= 0) "[Binary data, $length bytes]" else "[Binary data]"
+  }
 }

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/modules/network/NetworkEventUtilTest.kt

@@ -5,6 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+@file:Suppress("DEPRECATION_ERROR") // Conflicting okhttp versions
+
 package com.facebook.react.modules.network
 
 import com.facebook.react.bridge.Arguments
@@ -15,7 +17,13 @@ import com.facebook.react.internal.featureflags.ReactNativeFeatureFlags
 import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsDefaults
 import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsForTests
 import com.facebook.testutils.shadows.ShadowArguments
+import java.io.ByteArrayInputStream
 import java.net.SocketTimeoutException
+import okhttp3.MediaType
+import okhttp3.MediaType.Companion.toMediaTypeOrNull
+import okhttp3.MultipartBody
+import okhttp3.RequestBody
+import okhttp3.RequestBody.Companion.toRequestBody
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.After
 import org.junit.Before
@@ -292,6 +300,84 @@ class NetworkEventUtilTest {
     assertThat(args.getString(3)).isEqualTo(url)
   }
 
+  @Test
+  fun testGetRequestBodyPreviewReturnsNullForNullBody() {
+    assertThat(NetworkEventUtil.getRequestBodyPreview(null)).isNull()
+  }
+
+  @Test
+  fun testGetRequestBodyPreviewReturnsBodyForStringRequest() {
+    val payload = """{"key":"value"}"""
+    val body = payload.toRequestBody("application/json".toMediaTypeOrNull())
+
+    assertThat(NetworkEventUtil.getRequestBodyPreview(body)).isEqualTo(payload)
+  }
+
+  @Test
+  fun testGetRequestBodyPreviewUnwrapsProgressRequestBody() {
+    val payload = "hello world"
+    val inner = payload.toRequestBody("text/plain".toMediaTypeOrNull())
+    val wrapped = ProgressRequestBody(inner) { _, _, _ -> }
+
+    assertThat(NetworkEventUtil.getRequestBodyPreview(wrapped)).isEqualTo(payload)
+  }
+
+  @Test
+  fun testGetRequestBodyPreviewMultipartWithTextParts() {
+    val body =
+        MultipartBody.Builder("test-boundary")
+            .setType(MultipartBody.FORM)
+            .addFormDataPart("field1", "value1")
+            .addFormDataPart("field2", "value2")
+            .build()
+
+    val preview = NetworkEventUtil.getRequestBodyPreview(body)
+
+    assertThat(preview).isNotNull()
+    assertThat(preview).contains("--test-boundary")
+    assertThat(preview).contains("--test-boundary--")
+    assertThat(preview).contains("name=\"field1\"")
+    assertThat(preview).contains("value1")
+    assertThat(preview).contains("name=\"field2\"")
+    assertThat(preview).contains("value2")
+    assertThat(preview).doesNotContain("[Preview unavailable]")
+  }
+
+  @Test
+  fun testGetRequestBodyPreviewMultipartWithFilePartReplacesBinaryContent() {
+    val fileBytes = ByteArray(2048) { it.toByte() }
+    val streamingPart =
+        RequestBodyUtil.create(MediaType.parse("application/octet-stream"), ByteArrayInputStream(fileBytes))
+    val body =
+        MultipartBody.Builder("test-boundary")
+            .setType(MultipartBody.FORM)
+            .addFormDataPart("description", "an image")
+            .addFormDataPart("file", "photo.jpg", streamingPart)
+            .build()
+
+    val preview = NetworkEventUtil.getRequestBodyPreview(body)
+
+    assertThat(preview).isNotNull()
+    assertThat(preview).contains("--test-boundary")
+    assertThat(preview).contains("name=\"description\"")
+    assertThat(preview).contains("an image")
+    assertThat(preview).contains("name=\"file\"")
+    assertThat(preview).contains("filename=\"photo.jpg\"")
+    assertThat(preview).contains("[Binary data, 2048 bytes]")
+    assertThat(preview).doesNotContain("[Preview unavailable]")
+  }
+
+  @Test
+  fun testGetRequestBodyPreviewSingleOneShotBodyShowsPlaceholder() {
+    val fileBytes = ByteArray(512) { it.toByte() }
+    val body =
+        RequestBodyUtil.create(MediaType.parse("application/octet-stream"), ByteArrayInputStream(fileBytes))
+
+    val preview = NetworkEventUtil.getRequestBodyPreview(body)
+
+    assertThat(preview).isEqualTo("[Binary data, 512 bytes]")
+  }
+
   @Test
   fun testNullReactContext() {
     val url = "http://example.com"