Structured errors for PostgreSQL DB errors

Signed-off-by: itowlson <ivan.towlson@fermyon.com>

Author: itowlson

crates/factor-outbound-pg/src/client.rs

@@ -29,6 +29,48 @@ pub trait Client {
     ) -> Result<RowSet, v4::Error>;
 }
 
+/// Extract weak-typed error data for WIT purposes
+fn pg_extras(dbe: &tokio_postgres::error::DbError) -> Vec<(String, String)> {
+    let mut extras = vec![];
+
+    macro_rules! pg_extra {
+        ( $n:ident ) => {
+            if let Some(value) = dbe.$n() {
+                extras.push((stringify!($n).to_owned(), value.to_string()));
+            }
+        };
+    }
+
+    pg_extra!(column);
+    pg_extra!(constraint);
+    pg_extra!(routine);
+    pg_extra!(hint);
+    pg_extra!(table);
+    pg_extra!(datatype);
+    pg_extra!(schema);
+    pg_extra!(file);
+    pg_extra!(line);
+    pg_extra!(where_);
+
+    extras
+}
+
+fn query_failed(e: tokio_postgres::error::Error) -> v4::Error {
+    let flattened = format!("{e:?}");
+    let query_error = match e.as_db_error() {
+        None => v4::QueryError::Text(flattened),
+        Some(dbe) => v4::QueryError::DbError(v4::DbError {
+            as_text: flattened,
+            severity: dbe.severity().to_owned(),
+            code: dbe.code().code().to_owned(),
+            message: dbe.message().to_owned(),
+            detail: dbe.detail().map(|s| s.to_owned()),
+            extras: pg_extras(dbe),
+        }),
+    };
+    v4::Error::QueryFailed(query_error)
+}
+
 #[async_trait]
 impl Client for TokioClient {
     async fn build_client(address: &str) -> Result<Self>
@@ -70,7 +112,7 @@ impl Client for TokioClient {
 
         self.execute(&statement, params_refs.as_slice())
             .await
-            .map_err(|e| v4::Error::QueryFailed(format!("{e:?}")))
+            .map_err(query_failed)
     }
 
     async fn query(
@@ -92,7 +134,7 @@ impl Client for TokioClient {
         let results = self
             .query(&statement, params_refs.as_slice())
             .await
-            .map_err(|e| v4::Error::QueryFailed(format!("{e:?}")))?;
+            .map_err(query_failed)?;
 
         if results.is_empty() {
             return Ok(RowSet {
@@ -106,7 +148,7 @@ impl Client for TokioClient {
             .iter()
             .map(convert_row)
             .collect::<Result<Vec<_>, _>>()
-            .map_err(|e| v4::Error::QueryFailed(format!("{e:?}")))?;
+            .map_err(|e| v4::Error::QueryFailed(v4::QueryError::Text(format!("{e:?}"))))?;
 
         Ok(RowSet { columns, rows })
     }

crates/world/src/conversions.rs

@@ -376,7 +376,7 @@ mod rdbms_types {
             match error {
                 pg4::Error::ConnectionFailed(e) => v1::postgres::PgError::ConnectionFailed(e),
                 pg4::Error::BadParameter(e) => v1::postgres::PgError::BadParameter(e),
-                pg4::Error::QueryFailed(e) => v1::postgres::PgError::QueryFailed(e),
+                pg4::Error::QueryFailed(e) => v1::postgres::PgError::QueryFailed(pg_error_text(e)),
                 pg4::Error::ValueConversionFailed(e) => {
                     v1::postgres::PgError::ValueConversionFailed(e)
                 }
@@ -390,7 +390,7 @@ mod rdbms_types {
             match error {
                 pg4::Error::ConnectionFailed(e) => v2::rdbms_types::Error::ConnectionFailed(e),
                 pg4::Error::BadParameter(e) => v2::rdbms_types::Error::BadParameter(e),
-                pg4::Error::QueryFailed(e) => v2::rdbms_types::Error::QueryFailed(e),
+                pg4::Error::QueryFailed(e) => v2::rdbms_types::Error::QueryFailed(pg_error_text(e)),
                 pg4::Error::ValueConversionFailed(e) => {
                     v2::rdbms_types::Error::ValueConversionFailed(e)
                 }
@@ -404,12 +404,19 @@ mod rdbms_types {
             match error {
                 pg4::Error::ConnectionFailed(e) => pg3::Error::ConnectionFailed(e),
                 pg4::Error::BadParameter(e) => pg3::Error::BadParameter(e),
-                pg4::Error::QueryFailed(e) => pg3::Error::QueryFailed(e),
+                pg4::Error::QueryFailed(e) => pg3::Error::QueryFailed(pg_error_text(e)),
                 pg4::Error::ValueConversionFailed(e) => pg3::Error::ValueConversionFailed(e),
                 pg4::Error::Other(e) => pg3::Error::Other(e),
             }
         }
     }
+
+    pub fn pg_error_text(error: pg4::QueryError) -> String {
+        match error {
+            pg4::QueryError::Text(text) => text,
+            pg4::QueryError::DbError(e) => e.as_text,
+        }
+    }
 }
 
 mod postgres {

wit/deps/spin-postgres@4.0.0/postgres.wit

@@ -5,11 +5,29 @@ interface postgres {
   variant error {
       connection-failed(string),
       bad-parameter(string),
-      query-failed(string),
+      query-failed(query-error),
       value-conversion-failed(string),
       other(string)
   }
 
+  variant query-error {
+      /// An error occurred but we do not have structured info for it
+      text(string),
+      /// Postgres returned a structured database error
+      db-error(db-error),
+  }
+
+  record db-error {
+      /// Stringised version of the error. This is primarily to facilitate migration of older code.
+      as-text: string,
+      severity: string,
+      code: string,
+      message: string,
+      detail: option<string>,
+      /// Any error information provided by Postgres and not captured above.
+      extras: list<tuple<string, string>>,
+  }
+
   /// Data types for a database column
   variant db-data-type {
       boolean,