feat(logging): selective error message logging by error type

Previously, all errors were logged as generic errors. This enhancement introduces selective logging of warnings
and errors based on their error type. Additionally, message interpolation has been introduced to resolve error message
placeholders into human-readable text.

lib/resolvers/error.js

@@ -2,6 +2,7 @@ const cds = require('@sap/cds')
 const LOG_CDS = cds.log()
 const LOG_GRAPHQL = cds.log('graphql')
 const { normalizeError } = require('@sap/cds/libx/_runtime/common/error/frontend')
+const { getErrorMessage } = require('@sap/cds/libx/_runtime/common/error/utils')
 const { GraphQLError } = require('graphql')
 const { IS_PRODUCTION } = require('../utils')
 
@@ -31,14 +32,49 @@ const _cdsToGraphQLError = (context, err) => {
 }
 
 const _ensureError = error => (error instanceof Error ? error : new Error(error))
+const _clone = obj => Object.create(Object.getPrototypeOf(obj), Object.getOwnPropertyDescriptors(obj))
 
 const handleCDSError = (context, error) => {
   error = _ensureError(error)
-  // TODO: choose log level depending on type of error analogous to OData adapter
-  if (LOG_CDS._error) LOG_CDS.error(error)
+  _log(context.req, error)
   return _cdsToGraphQLError(context, error)
 }
 
+const _log = (req, error) => {
+  // do not log standard errors, e.g. TypeError
+  if (error.code === undefined && error.details === undefined) return
+
+  // log errors and warnings only
+  if (LOG_CDS.level <= cds.log.levels.WARN) return
+
+  // Clone of the original error object to prevent mutation and unintended side-effects.
+  // Notice that the cloned error is logged to standard output in its default language,
+  // whether the original error message is locale-dependent as it is usually sent in the
+  // HTTP response to HTTP Clients to be displayed in the user interface.
+  const error2log = _clone(error)
+
+  // interpolate message placeholder to default language
+  error2log.message = getErrorMessage(error)
+  if (error.details) {
+    error2log.details = error.details.map(error => {
+      const clone = _clone(error)
+      clone.message = getErrorMessage(error)
+      return clone
+    })
+  }
+
+  const reqClone = _clone(req)
+  const statusCode = normalizeError(error2log, reqClone).statusCode
+
+  if (statusCode >= 400 && statusCode < 500) {
+    // client error
+    if (LOG_CDS._warn) LOG_CDS.warn(error2log)
+  } else {
+    // server error
+    if (LOG_CDS._error) LOG_CDS.error(error2log)
+  }
+}
+
 const formatError = error => {
   // CDS errors have already been logged and already have a stacktrace in extensions
   if (error.originalError?._cdsError) return error

lib/resolvers/response.js

@@ -3,8 +3,8 @@ const { handleCDSError } = require('./error')
 const setResponse = async (context, response, key, value) => {
   try {
     response[key] = await value
-  } catch (e) {
-    response[key] = handleCDSError(context, e)
+  } catch (error) {
+    response[key] = handleCDSError(context, error)
   }
 }