Redefine result[] error object as ref (see issue #1796) (#1797)

details:
 This does not affect the legacy interface which is the production one,
 currently.

nimbus/db/core_db/base.nim

@@ -21,7 +21,7 @@ import
 export
   CoreDbBackendRef,
   CoreDbCaptFlags,
-  CoreDbError,
+  CoreDbErrorRef,
   CoreDbKvtBackendRef,
   CoreDbMptBackendRef,
   CoreDbRef,
@@ -74,7 +74,7 @@ type
 
   CoreDxChldRef* = CoreDxKvtRef | CoreDxTrieRef | CoreDxTxRef | CoreDxTxID |
                    CoreDxCaptRef |
-                   CoreDbError |
+                   CoreDbErrorRef |
                    CoreDbBackendRef | CoreDbKvtBackendRef | CoreDbMptBackendRef
     ## Shortcut, all modules with a `parent`
 
@@ -194,7 +194,7 @@ proc backend*(db: CoreDbRef): CoreDbBackendRef =
   result = db.methods.backendFn()
   result.parent = db
 
-proc `$$`*(e: CoreDbError): string =
+proc `$$`*(e: CoreDbErrorRef): string =
   ## Pretty print error symbol, note that this directive may have side effects
   ## as it calls a backend function.
   e.parent.methods.errorPrintFn(e)

nimbus/db/core_db/base/base_desc.nim

@@ -31,7 +31,7 @@ const
   CoreDbPersistentTypes* = {LegacyDbPersistent}
 
 type
-  CoreDbRc*[T] = Result[T,CoreDbError]
+  CoreDbRc*[T] = Result[T,CoreDbErrorRef]
 
   CoreDbCaptFlags* {.pure.} = enum
     PersistPut
@@ -68,7 +68,7 @@ type
   # Sub-descriptor: Misc methods for main descriptor
   # --------------------------------------------------
   CoreDbBackendFn* = proc(): CoreDbBackendRef {.noRaise.}
-  CoreDbErrorPrintFn* = proc(e: CoreDbError): string {.noRaise.}
+  CoreDbErrorPrintFn* = proc(e: CoreDbErrorRef): string {.noRaise.}
   CoreDbInitLegaSetupFn* = proc() {.noRaise.}
 
   CoreDbMiscFns* = object
@@ -172,7 +172,7 @@ type
     new*: CoreDbConstructorFns
     methods*: CoreDbMiscFns
 
-  CoreDbError* = object of RootObj
+  CoreDbErrorRef* = ref object of RootRef
     ## Generic error object
     parent*: CoreDbRef
 

nimbus/db/core_db/base/validate.nim

@@ -59,7 +59,8 @@ proc validateConstructors(new: CoreDbConstructorFns) =
 
 # ------------
 
-proc validateMethodsDesc(e: CoreDbError) =
+proc validateMethodsDesc(e: CoreDbErrorRef) =
+  doAssert not e.isNil
   doAssert not e.parent.isNil
 
 proc validateMethodsDesc(eph: EphemMethodsDesc) =
@@ -111,7 +112,7 @@ proc validateMethodsDesc(db: CoreDbRef) =
 # Public debugging helpers
 # ------------------------------------------------------------------------------
 
-proc validate*(desc: MethodsDesc | EphemMethodsDesc | CoreDbError) =
+proc validate*(desc: MethodsDesc | EphemMethodsDesc | CoreDbErrorRef) =
   desc.validateMethodsDesc
 
 proc validate*(db: CoreDbRef) =

nimbus/db/core_db/legacy_db.nim

@@ -42,7 +42,7 @@ type
   LegacyCoreDbMptBE = ref object of CoreDbMptBackendRef
     mpt: HexaryTrie
 
-  LegacyCoreDbError = object of CoreDbError
+  LegacyCoreDbError = ref object of CoreDbErrorRef
     ctx: string     ## Context where the exception or error occured
     name: string    ## name of exception
     msg: string     ## Exception info
@@ -124,11 +124,13 @@ proc miscMethods(db: LegacyDbRef): CoreDbMiscFns =
     backendFn: proc(): CoreDbBackendRef =
       db.bless(LegacyCoreDbBE(base: db)),
 
-    errorPrintFn: proc(e: CoreDbError): string =
-      let e = e.LegacyCoreDbError
-      result &= "ctx=\"" & $e.ctx & "\"" & " , "
-      result &= "name=\"" & $e.name & "\"" & ", "
-      result &= "msg=\"" & $e.msg & "\"",
+    errorPrintFn: proc(e: CoreDbErrorRef): string =
+      if not e.isNil:
+        let e = e.LegacyCoreDbError
+        result &= "ctx=\"" & $e.ctx & "\"" & " , "
+        result &= "name=\"" & $e.name & "\"" & ", "
+        result &= "msg=\"" & $e.msg & "\""
+      discard,
 
     legacySetupFn: proc() =
       db.tdb.put(EMPTY_ROOT_HASH.data, @[0x80u8]))

nimbus/db/core_db/memory_only.nim

@@ -21,7 +21,7 @@ export
 
   # Not all symbols from the object sources will be exported by default
   CoreDbCaptFlags,
-  CoreDbError,
+  CoreDbErrorRef,
   CoreDbCaptRef,
   CoreDbKvtRef,
   CoreDbMptRef,