From 07508fb1108d7fb503471a433395838fd13567ed Mon Sep 17 00:00:00 2001
From: Joonas Koivunen <joonas@neon.tech>
Date: Fri, 15 Dec 2023 12:18:22 +0200
Subject: [PATCH] fix: better Json parsing errors (#6135)

Before any json parsing from the http api only returned errors were per
field errors. Now they are done using `serde_path_to_error`, which at
least helped greatly with the `disk_usage_eviction_run` used for
testing. I don't think this can conflict with anything added in #5310.
---
 Cargo.lock                    | 1 +
 libs/utils/Cargo.toml         | 2 ++
 libs/utils/src/http/json.rs   | 8 ++++++--
 pageserver/src/http/routes.rs | 4 +---
 4 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 71c2c976a7..7bf9209395 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5765,6 +5765,7 @@ dependencies = [
  "serde",
  "serde_assert",
  "serde_json",
+ "serde_path_to_error",
  "serde_with",
  "signal-hook",
  "strum",
diff --git a/libs/utils/Cargo.toml b/libs/utils/Cargo.toml
index ccf6f4f2d7..af0414daa2 100644
--- a/libs/utils/Cargo.toml
+++ b/libs/utils/Cargo.toml
@@ -50,6 +50,8 @@ const_format.workspace = true
 # why is it only here? no other crate should use it, streams are rarely needed.
 tokio-stream = { version = "0.1.14" }
 
+serde_path_to_error.workspace = true
+
 [dev-dependencies]
 byteorder.workspace = true
 bytes.workspace = true
diff --git a/libs/utils/src/http/json.rs b/libs/utils/src/http/json.rs
index 70e682cb76..7ca62561fe 100644
--- a/libs/utils/src/http/json.rs
+++ b/libs/utils/src/http/json.rs
@@ -25,8 +25,12 @@ pub async fn json_request_or_empty_body<T: for<'de> Deserialize<'de>>(
     if body.remaining() == 0 {
         return Ok(None);
     }
-    serde_json::from_reader(body.reader())
-        .context("Failed to parse json request")
+
+    let mut deser = serde_json::de::Deserializer::from_reader(body.reader());
+
+    serde_path_to_error::deserialize(&mut deser)
+        // intentionally stringify because the debug version is not helpful in python logs
+        .map_err(|e| anyhow::anyhow!("Failed to parse json request: {e}"))
         .map(Some)
         .map_err(ApiError::BadRequest)
 }
diff --git a/pageserver/src/http/routes.rs b/pageserver/src/http/routes.rs
index 14107557d9..102c9d9a6a 100644
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -1621,9 +1621,7 @@ async fn disk_usage_eviction_run(
         }
     }
 
-    let config = json_request::<Config>(&mut r)
-        .await
-        .map_err(|_| ApiError::BadRequest(anyhow::anyhow!("invalid JSON body")))?;
+    let config = json_request::<Config>(&mut r).await?;
 
     let usage = Usage {
         config,