Fix missing import in pooling implementation.

fiber_orm.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "1.0.4"
+version       = "2.1.1"
 author        = "Jonathan Bernard"
 description   = "Lightweight Postgres ORM for Nim."
 license       = "GPL-3.0"
@@ -11,4 +11,4 @@ srcDir        = "src"
 # Dependencies
 
 requires @["nim >= 1.4.0", "uuids"]
-requires "https://git.jdb-software.com/jdb/nim-namespaced-logging.git"
+requires "namespaced_logging >= 0.3.0"

src/fiber_orm.nim

@@ -104,26 +104,34 @@
 ##
 ## .. code-block:: Nim
 ##    proc getTodoItem*(db: TodoDB, id: UUID): TodoItem;
-##    proc getAllTodoItems*(db: TodoDB): seq[TodoItem];
+##
 ##    proc createTodoItem*(db: TodoDB, rec: TodoItem): TodoItem;
 ##    proc updateTodoItem*(db: TodoDB, rec: TodoItem): bool;
 ##    proc deleteTodoItem*(db: TodoDB, rec: TodoItem): bool;
 ##    proc deleteTodoItem*(db: TodoDB, id: UUID): bool;
 ##
+##    proc getAllTodoItems*(db: TodoDB,
+##      pagination = none[PaginationParams]()): seq[TodoItem];
+##
 ##    proc findTodoItemsWhere*(db: TodoDB, whereClause: string,
-##      values: varargs[string, dbFormat]): seq[TodoItem];
+##      values: varargs[string, dbFormat], pagination = none[PaginationParams]()
+##      ): seq[TodoItem];
 ##
 ##    proc getTimeEntry*(db: TodoDB, id: UUID): TimeEntry;
-##    proc getAllTimeEntries*(db: TodoDB): seq[TimeEntry];
 ##    proc createTimeEntry*(db: TodoDB, rec: TimeEntry): TimeEntry;
 ##    proc updateTimeEntry*(db: TodoDB, rec: TimeEntry): bool;
 ##    proc deleteTimeEntry*(db: TodoDB, rec: TimeEntry): bool;
 ##    proc deleteTimeEntry*(db: TodoDB, id: UUID): bool;
 ##
-##    proc findTimeEntriesWhere*(db: TodoDB, whereClause: string,
-##      values: varargs[string, dbFormat]): seq[TimeEntry];
+##    proc getAllTimeEntries*(db: TodoDB,
+##      pagination = none[PaginationParams]()): seq[TimeEntry];
 ##
-##    proc findTimeEntriesByTodoItemId(db: TodoDB, todoItemId: UUID): seq[TimeEntry];
+##    proc findTimeEntriesWhere*(db: TodoDB, whereClause: string,
+##      values: varargs[string, dbFormat], pagination = none[PaginationParams]()
+##      ): seq[TimeEntry];
+##
+##    proc findTimeEntriesByTodoItemId(db: TodoDB, todoItemId: UUID,
+##      pagination = none[PaginationParams]()): seq[TimeEntry];
 ##
 ## Object-Relational Modeling
 ## ==========================
@@ -274,11 +282,12 @@
 ##
 ## .. _pool.DbConnPool: fiber_orm/pool.html#DbConnPool
 ##
-import std/db_postgres, std/macros, std/options, std/sequtils, std/strutils
+import std/[db_common, logging, macros, options, sequtils, strutils]
 import namespaced_logging, uuids
 
 from std/unicode import capitalize
 
+import ./fiber_orm/db_common as fiber_db_common
 import ./fiber_orm/pool
 import ./fiber_orm/util
 
@@ -292,13 +301,24 @@ export
   util.rowToModel,
   util.tableName
 
-type NotFoundError* = object of CatchableError ##\
+type
+  PaginationParams* = object
+    pageSize*: int
+    offset*: int
+    orderBy*: Option[string]
+
+  PagedRecords*[T] = object
+    pagination*: Option[PaginationParams]
+    records*: seq[T]
+    totalRecords*: int
+
+  NotFoundError* = object of CatchableError ##\
     ## Error type raised when no record matches a given ID
 
 var logNs {.threadvar.}: LoggingNamespace
 
 template log(): untyped =
-  if logNs.isNil: logNs = initLoggingNamespace(name = "fiber_orm", level = lvlNotice)
+  if logNs.isNil: logNs = getLoggerForNamespace(namespace = "fiber_orm", level = lvlNotice)
   logNs
 
 proc newMutateClauses(): MutateClauses =
@@ -307,7 +327,7 @@ proc newMutateClauses(): MutateClauses =
     placeholders: @[],
     values: @[])
 
-proc createRecord*[T](db: DbConn, rec: T): T =
+proc createRecord*[D: DbConnType, T](db: D, rec: T): T =
   ## Create a new record. `rec` is expected to be a `model class`_. The `id`
   ## field is only set if it is non-empty (see `ID Field`_ for details).
   ##
@@ -330,7 +350,7 @@ proc createRecord*[T](db: DbConn, rec: T): T =
 
   result = rowToModel(T, newRow)
 
-proc updateRecord*[T](db: DbConn, rec: T): bool =
+proc updateRecord*[D: DbConnType, T](db: D, rec: T): bool =
   ## Update a record by id. `rec` is expected to be a `model class`_.
   var mc = newMutateClauses()
   populateMutateClauses(rec, false, mc)
@@ -346,13 +366,13 @@ proc updateRecord*[T](db: DbConn, rec: T): bool =
 
   return numRowsUpdated > 0;
 
-template deleteRecord*(db: DbConn, modelType: type, id: typed): untyped =
+template deleteRecord*[D: DbConnType](db: D, modelType: type, id: typed): untyped =
   ## Delete a record by id.
   let sqlStmt = "DELETE FROM " & tableName(modelType) & " WHERE id = ?"
   log().debug "deleteRecord: [" & sqlStmt & "] id: " & $id
   db.tryExec(sql(sqlStmt), $id)
 
-proc deleteRecord*[T](db: DbConn, rec: T): bool =
+proc deleteRecord*[D: DbConnType, T](db: D, rec: T): bool =
   ## Delete a record by `id`_.
   ##
   ## .. _id: #model-class-id-field
@@ -360,7 +380,7 @@ proc deleteRecord*[T](db: DbConn, rec: T): bool =
   log().debug "deleteRecord: [" & sqlStmt & "] id: " & $rec.id
   return db.tryExec(sql(sqlStmt), $rec.id)
 
-template getRecord*(db: DbConn, modelType: type, id: typed): untyped =
+template getRecord*[D: DbConnType](db: D, modelType: type, id: typed): untyped =
   ## Fetch a record by id.
   let sqlStmt =
     "SELECT " & columnNamesForModel(modelType).join(",") &
@@ -375,37 +395,114 @@ template getRecord*(db: DbConn, modelType: type, id: typed): untyped =
 
   rowToModel(modelType, row)
 
-template findRecordsWhere*(db: DbConn, modelType: type, whereClause: string, values: varargs[string, dbFormat]): untyped =
+template findRecordsWhere*[D: DbConnType](
+    db: D,
+    modelType: type,
+    whereClause: string,
+    values: varargs[string, dbFormat],
+    page: Option[PaginationParams]): untyped =
   ## Find all records matching a given `WHERE` clause. The number of elements in
   ## the `values` array must match the number of placeholders (`?`) in the
   ## provided `WHERE` clause.
-  let sqlStmt =
+  var fetchStmt =
     "SELECT " & columnNamesForModel(modelType).join(",") &
     " FROM " & tableName(modelType) &
     " WHERE " & whereClause
 
-  log().debug "findRecordsWhere: [" & sqlStmt & "] values: (" & values.join(", ") & ")"
-  db.getAllRows(sql(sqlStmt), values).mapIt(rowToModel(modelType, it))
+  var countStmt =
+    "SELECT COUNT(*) FROM " & tableName(modelType) &
+    " WHERE " & whereClause
 
-template getAllRecords*(db: DbConn, modelType: type): untyped =
+  if page.isSome:
+    let p = page.get
+    if p.orderBy.isSome:
+      fetchStmt &= " ORDER BY " & p.orderBy.get
+    else:
+      fetchStmt &= " ORDER BY id"
+
+    fetchStmt &= " LIMIT " & $p.pageSize &
+                 " OFFSET " & $p.offset
+
+  log().debug "findRecordsWhere: [" & fetchStmt & "] values: (" & values.join(", ") & ")"
+  let records = db.getAllRows(sql(fetchStmt), values).mapIt(rowToModel(modelType, it))
+
+  PagedRecords[modelType](
+    pagination: page,
+    records: records,
+    totalRecords:
+      if page.isNone: records.len
+      else: db.getRow(sql(countStmt), values)[0].parseInt)
+
+template getAllRecords*[D: DbConnType](
+    db: D,
+    modelType: type,
+    page: Option[PaginationParams]): untyped =
   ## Fetch all records of the given type.
-  let sqlStmt =
+  var fetchStmt =
     "SELECT " & columnNamesForModel(modelType).join(",") &
     " FROM " & tableName(modelType)
 
-  log().debug "getAllRecords: [" & sqlStmt & "]"
-  db.getAllRows(sql(sqlStmt)).mapIt(rowToModel(modelType, it))
+  var countStmt = "SELECT COUNT(*) FROM " & tableName(modelType)
 
-template findRecordsBy*(db: DbConn, modelType: type, lookups: seq[tuple[field: string, value: string]]): untyped =
+  if page.isSome:
+    let p = page.get
+    if p.orderBy.isSome:
+      fetchStmt &= " ORDER BY " & p.orderBy.get
+    else:
+      fetchStmt &= " ORDER BY id"
+
+    fetchStmt &= " LIMIT " & $p.pageSize &
+                 " OFFSET " & $p.offset
+
+  log().debug "getAllRecords: [" & fetchStmt & "]"
+  let records = db.getAllRows(sql(fetchStmt)).mapIt(rowToModel(modelType, it))
+
+  PagedRecords[modelType](
+    pagination: page,
+    records: records,
+    totalRecords:
+      if page.isNone: records.len
+      else: db.getRow(sql(countStmt))[0].parseInt)
+
+
+template findRecordsBy*[D: DbConnType](
+    db: D,
+    modelType: type,
+    lookups: seq[tuple[field: string, value: string]],
+    page: Option[PaginationParams]): untyped =
   ## Find all records matching the provided lookup values.
-  let sqlStmt =
-    "SELECT " & columnNamesForModel(modelType).join(",") &
-    " FROM " & tableName(modelType) &
-    " WHERE " & lookups.mapIt(it.field & " = ?").join(" AND ")
+  let whereClause = lookups.mapIt(it.field & " = ?").join(" AND ")
   let values = lookups.mapIt(it.value)
 
-  log().debug "findRecordsBy: [" & sqlStmt & "] values (" & values.join(", ") & ")"
-  db.getAllRows(sql(sqlStmt), values).mapIt(rowToModel(modelType, it))
+  var fetchStmt =
+    "SELECT " & columnNamesForModel(modelType).join(",") &
+    " FROM " & tableName(modelType) &
+    " WHERE " & whereClause
+
+  var countStmt =
+    "SELECT COUNT(*) FROM " & tableName(modelType) &
+    " WHERE " & whereClause
+
+  if page.isSome:
+    let p = page.get
+    if p.orderBy.isSome:
+      fetchStmt &= " ORDER BY " & p.orderBy.get
+    else:
+      fetchStmt &= " ORDER BY id"
+
+    fetchStmt &= " LIMIT " & $p.pageSize &
+                 " OFFSET " & $p.offset
+
+  log().debug "findRecordsBy: [" & fetchStmt & "] values (" & values.join(", ") & ")"
+  let records = db.getAllRows(sql(fetchStmt), values).mapIt(rowToModel(modelType, it))
+
+  PagedRecords[modelType](
+    pagination: page,
+    records: records,
+    totalRecords:
+      if page.isNone: records.len
+      else: db.getRow(sql(countStmt), values)[0].parseInt)
+
 
 macro generateProcsForModels*(dbType: type, modelTypes: openarray[type]): untyped =
   ## Generate all standard access procedures for the given model types. For a
@@ -430,6 +527,10 @@ macro generateProcsForModels*(dbType: type, modelTypes: openarray[type]): untype
   result = newStmtList()
 
   for t in modelTypes:
+    if t.getType[1].typeKind == ntyRef:
+      raise newException(ValueError,
+        "fiber_orm model object must be objects, not refs")
+
     let modelName = $(t.getType[1])
     let getName = ident("get" & modelName)
     let getAllName = ident("getAll" & pluralize(modelName))
@@ -442,12 +543,16 @@ macro generateProcsForModels*(dbType: type, modelTypes: openarray[type]): untype
       proc `getName`*(db: `dbType`, id: `idType`): `t` =
         db.withConn: result = getRecord(conn, `t`, id)
 
-      proc `getAllName`*(db: `dbType`): seq[`t`] =
-        db.withConn: result = getAllRecords(conn, `t`)
+      proc `getAllName`*(db: `dbType`, pagination = none[PaginationParams]()): PagedRecords[`t`] =
+        db.withConn: result = getAllRecords(conn, `t`, pagination)
 
-      proc `findWhereName`*(db: `dbType`, whereClause: string, values: varargs[string, dbFormat]): seq[`t`] =
+      proc `findWhereName`*(
+          db: `dbType`,
+          whereClause: string,
+          values: varargs[string, dbFormat],
+          pagination = none[PaginationParams]()): PagedRecords[`t`] =
         db.withConn:
-          result = findRecordsWhere(conn, `t`, whereClause, values)
+          result = findRecordsWhere(conn, `t`, whereClause, values, pagination)
 
       proc `createName`*(db: `dbType`, rec: `t`): `t` =
         db.withConn: result = createRecord(conn, rec)
@@ -478,7 +583,7 @@ macro generateLookup*(dbType: type, modelType: type, fields: seq[string]): untyp
 
   # Create proc skeleton
   result = quote do:
-    proc `procName`*(db: `dbType`): seq[`modelType`] =
+    proc `procName`*(db: `dbType`): PagedRecords[`modelType`] =
       db.withConn: result = findRecordsBy(conn, `modelType`)
 
   var callParams = quote do: @[]
@@ -496,12 +601,18 @@ macro generateLookup*(dbType: type, modelType: type, fields: seq[string]): untyp
     # Build up the AST for the inner procedure call
     callParams[1].add(paramTuple)
 
+  # Add the optional pagination parameters to the generated proc definition
+  result[3].add(newIdentDefs(
+    ident("pagination"), newEmptyNode(),
+    quote do: none[PaginationParams]()))
+
   # Add the call params to the inner procedure call
   # result[6][0][1][0][1] is
   #   ProcDef -> [6]: StmtList (body) -> [0]: Call ->
   #     [1]: StmtList (withConn body) -> [0]: Asgn (result =) ->
   #     [1]: Call (inner findRecords invocation)
   result[6][0][1][0][1].add(callParams)
+  result[6][0][1][0][1].add(quote do: pagination)
 
 macro generateProcsForFieldLookups*(dbType: type, modelsAndFields: openarray[tuple[t: type, fields: seq[string]]]): untyped =
   result = newStmtList()
@@ -514,7 +625,7 @@ macro generateProcsForFieldLookups*(dbType: type, modelsAndFields: openarray[tup
 
     # Create proc skeleton
     let procDefAST = quote do:
-      proc `procName`*(db: `dbType`): seq[`modelType`] =
+      proc `procName`*(db: `dbType`): PagedRecords[`modelType`] =
         db.withConn: result = findRecordsBy(conn, `modelType`)
 
     var callParams = quote do: @[]
@@ -528,15 +639,22 @@ macro generateProcsForFieldLookups*(dbType: type, modelsAndFields: openarray[tup
       procDefAST[3].add(newIdentDefs(ident(n), ident("string")))
       callParams[1].add(paramTuple)
 
+    # Add the optional pagination parameters to the generated proc definition
+    procDefAST[3].add(newIdentDefs(
+      ident("pagination"), newEmptyNode(),
+      quote do: none[PaginationParams]()))
+
     procDefAST[6][0][1][0][1].add(callParams)
+    procDefAST[6][0][1][0][1].add(quote do: pagination)
 
     result.add procDefAST
 
-proc initPool*(
-    connect: proc(): DbConn,
+proc initPool*[D: DbConnType](
+    connect: proc(): D,
     poolSize = 10,
     hardCap = false,
-    healthCheckQuery = "SELECT 'true' AS alive"): DbConnPool =
+    healthCheckQuery = "SELECT 'true' AS alive"): DbConnPool[D] =
+
   ## Initialize a new DbConnPool. See the `initDb` procedure in the `Example
   ## Fiber ORM Usage`_ for an example
   ##
@@ -554,13 +672,13 @@ proc initPool*(
   ##
   ## .. _Example Fiber ORM Usage: #basic-usage-example-fiber-orm-usage
 
-  initDbConnPool(DbConnPoolConfig(
+  initDbConnPool(DbConnPoolConfig[D](
     connect: connect,
     poolSize: poolSize,
     hardCap: hardCap,
     healthCheckQuery: healthCheckQuery))
 
-template inTransaction*(db: DbConnPool, body: untyped) =
+template inTransaction*[D: DbConnType](db: DbConnPool[D], body: untyped) =
   pool.withConn(db):
     conn.exec(sql"BEGIN TRANSACTION")
     try:

src/fiber_orm/db_common.nim

@@ -0,0 +1,3 @@
+import std/[db_postgres, db_sqlite]
+
+type DbConnType* = db_postgres.DbConn or db_sqlite.DbConn

src/fiber_orm/pool.nim

@@ -4,65 +4,70 @@
 
 ## Simple database connection pooling implementation compatible with Fiber ORM.
 
-import std/db_postgres, std/sequtils, std/strutils, std/sugar
+import std/[db_common, logging, sequtils, strutils, sugar]
+
+from std/db_sqlite import getRow, close
+from std/db_postgres import getRow, close
 
 import namespaced_logging
-
+import ./db_common as fiber_db_common
 
 type
-  DbConnPoolConfig* = object
-    connect*: () -> DbConn  ## Factory procedure to create a new DBConn
+  DbConnPoolConfig*[D: DbConnType] = object
+    connect*: () -> D   ## Factory procedure to create a new DBConn
     poolSize*: int      ## The pool capacity.
+
     hardCap*: bool      ## Is the pool capacity a hard cap?
                         ##
-                   ## When `false`, the pool can grow beyond the configured
-                   ## capacity, but will release connections down to the its
-                   ## capacity (no less than `poolSize`).
+                        ## When `false`, the pool can grow beyond the
+                        ## configured capacity, but will release connections
+                        ## down to the its capacity (no less than `poolSize`).
                         ##
                         ## When `true` the pool will not create more than its
-                   ## configured capacity.  It a connection is requested, none
-                   ## are free, and the pool is at capacity, this will result
-                   ## in an Error being raised.
+                        ## configured capacity.  It a connection is requested,
+                        ## none are free, and the pool is at capacity, this
+                        ## will result in an Error being raised.
+
     healthCheckQuery*: string ## Should be a simple and fast SQL query that the
                               ## pool can use to test the liveliness of pooled
                               ## connections.
 
-  PooledDbConn = ref object
-    conn: DbConn
+  PooledDbConn[D: DbConnType] = ref object
+    conn: D
     id: int
     free: bool
 
-  DbConnPool* = ref object
+  DbConnPool*[D: DbConnType] = ref object
     ## Database connection pool
-    conns: seq[PooledDbConn]
-    cfg: DbConnPoolConfig
+    conns: seq[PooledDbConn[D]]
+    cfg: DbConnPoolConfig[D]
     lastId: int
 
 var logNs {.threadvar.}: LoggingNamespace
 
 template log(): untyped =
-  if logNs.isNil: logNs = initLoggingNamespace(name = "fiber_orm/pool", level = lvlNotice)
+  if logNs.isNil: logNs = getLoggerForNamespace(namespace = "fiber_orm/pool", level = lvlNotice)
   logNs
 
-proc initDbConnPool*(cfg: DbConnPoolConfig): DbConnPool =
+proc initDbConnPool*[D: DbConnType](cfg: DbConnPoolConfig[D]): DbConnPool[D] =
   log().debug("Initializing new pool (size: " & $cfg.poolSize)
-  result = DbConnPool(
+  result = DbConnPool[D](
     conns: @[],
     cfg: cfg)
 
-proc newConn(pool: DbConnPool): PooledDbConn =
+proc newConn[D: DbConnType](pool: DbConnPool[D]): PooledDbConn[D] =
   log().debug("Creating a new connection to add to the pool.")
   pool.lastId += 1
   let conn = pool.cfg.connect()
-  result = PooledDbConn(
+  result = PooledDbConn[D](
     conn: conn,
     id: pool.lastId,
     free: true)
   pool.conns.add(result)
 
-proc maintain(pool: DbConnPool): void =
+proc maintain[D: DbConnType](pool: DbConnPool[D]): void =
   log().debug("Maintaining pool. $# connections." % [$pool.conns.len])
-  pool.conns.keepIf(proc (pc: PooledDbConn): bool =
+  pool.conns.keepIf(proc (pc: PooledDbConn[D]): bool =
     if not pc.free: return true
 
     try:
@@ -91,7 +96,7 @@ proc maintain(pool: DbConnPool): void =
         "Trimming pool size. Culled $# free connections. $# connections remaining." %
         [$toCull.len, $pool.conns.len])
 
-proc take*(pool: DbConnPool): tuple[id: int, conn: DbConn] =
+proc take*[D: DbConnType](pool: DbConnPool[D]): tuple[id: int, conn: D] =
   ## Request a connection from the pool. Returns a DbConn if the pool has free
   ## connections, or if it has the capacity to create a new connection. If the
   ## pool is configured with a hard capacity limit and is out of free
@@ -113,13 +118,13 @@ proc take*(pool: DbConnPool): tuple[id: int, conn: DbConn] =
   log().debug("Reserve connection $#" % [$reserved.id])
   return (id: reserved.id, conn: reserved.conn)
 
-proc release*(pool: DbConnPool, connId: int): void =
+proc release*[D: DbConnType](pool: DbConnPool[D], connId: int): void =
   ## Release a connection back to the pool.
   log().debug("Reclaiming released connaction $#" % [$connId])
   let foundConn = pool.conns.filterIt(it.id == connId)
   if foundConn.len > 0: foundConn[0].free = true
 
-template withConn*(pool: DbConnPool, stmt: untyped): untyped =
+template withConn*[D: DbConnType](pool: DbConnPool[D], stmt: untyped): untyped =
   ## Convenience template to provide a connection from the pool for use in a
   ## statement block, automatically releasing that connnection when done.
   ##

src/fiber_orm/util.nim

@@ -3,10 +3,10 @@
 # Copyright 2019 Jonathan Bernard <jonathan@jdbernard.com>
 
 ## Utility methods used internally by Fiber ORM.
-import json, macros, options, sequtils, strutils, times, unicode,
-  uuids
+import std/[json, macros, options, sequtils, strutils, times, unicode]
+import uuids
 
-import nre except toSeq
+import std/nre except toSeq
 
 type
   MutateClauses* = object
@@ -207,21 +207,14 @@ proc parseDbArray*(val: string): seq[string] =
   if not (parseState == inQuote) and curStr.len > 0:
     result.add(curStr)
 
-proc createParseStmt*(t, value: NimNode): NimNode =
+func createParseStmt*(t, value: NimNode): NimNode =
   ## Utility method to create the Nim cod required to parse a value coming from
   ## the a database query. This is used by functions like `rowToModel` to parse
   ## the dataabase columns into the Nim object fields.
 
-  #echo "Creating parse statment for ", t.treeRepr
   if t.typeKind == ntyObject:
 
-    if t.getType == UUID.getType:
-      result = quote do: parseUUID(`value`)
-
-    elif t.getType == DateTime.getType:
-      result = quote do: parsePGDatetime(`value`)
-
-    elif t.getTypeInst == Option.getType:
+    if t.getTypeInst == Option.getType:
       var innerType = t.getTypeImpl[2][0] # start at the first RecList
       # If the value is a non-pointer type, there is another inner RecList
       if innerType.kind == nnkRecList: innerType = innerType[0]
@@ -232,8 +225,28 @@ proc createParseStmt*(t, value: NimNode): NimNode =
         if `value`.len == 0:  none[`innerType`]()
         else:                 some(`parseStmt`)
 
+    elif t.getType == UUID.getType:
+      result = quote do: parseUUID(`value`)
+
+    elif t.getType == DateTime.getType:
+      result = quote do: parsePGDatetime(`value`)
+
     else: error "Unknown value object type: " & $t.getTypeInst
 
+  elif t.typeKind == ntyGenericInst:
+
+    if t.kind == nnkBracketExpr and
+       t.len > 0 and
+       t[0] == Option.getType:
+
+      var innerType = t.getTypeInst[1]
+      let parseStmt = createParseStmt(innerType, value)
+      result = quote do:
+        if `value`.len == 0:  none[`innerType`]()
+        else:                 some(`parseStmt`)
+
+    else: error "Unknown generic instance type: " & $t.getTypeInst
+
   elif t.typeKind == ntyRef:
 
     if $t.getTypeInst == "JsonNode":
@@ -268,28 +281,72 @@ proc createParseStmt*(t, value: NimNode): NimNode =
   else:
     error "Unknown value type: " & $t.typeKind
 
+func fields(t: NimNode): seq[tuple[fieldIdent: NimNode, fieldType: NimNode]] =
+  #[
+  debugEcho "T: " & t.treeRepr
+  debugEcho "T.kind: " & $t.kind
+  debugEcho "T.typeKind: " & $t.typeKind
+  debugEcho "T.GET_TYPE[1]: " & t.getType[1].treeRepr
+  debugEcho "T.GET_TYPE[1].kind: " & $t.getType[1].kind
+  debugEcho "T.GET_TYPE[1].typeKind: " & $t.getType[1].typeKind
+
+  debugEcho "T.GET_TYPE: " & t.getType.treeRepr
+  debugEcho "T.GET_TYPE[1].GET_TYPE: " & t.getType[1].getType.treeRepr
+  ]#
+
+  # Get the object type AST, with base object (if present) and record list.
+  var objDefAst: NimNode
+  if t.typeKind == ntyObject: objDefAst = t.getType
+  elif t.typeKind == ntyTypeDesc:
+    # In this case we have a type AST that is like:
+    # BracketExpr
+    #   Sym "typeDesc"
+    #   Sym "ModelType"
+    objDefAst = t.
+      getType[1].         # get the Sym "ModelType"
+      getType             # get the object definition type
+
+    if objDefAst.kind != nnkObjectTy:
+      error ("unable to enumerate the fields for model type '$#', " &
+        "tried to resolve the type of the provided symbol to an object " &
+        "definition (nnkObjectTy) but got a '$#'.\pAST:\p$#") % [
+          $t, $objDefAst.kind, objDefAst.treeRepr ]
+  else:
+    error ("unable to enumerate the fields for model type '$#', " &
+      "expected a symbol with type ntyTypeDesc but got a '$#'.\pAST:\p$#") % [
+        $t, $t.typeKind, t.treeRepr ]
+
+  # At this point objDefAst should look something like:
+  # ObjectTy
+  #   Empty
+  #   Sym "BaseObject"" | Empty
+  #   RecList
+  #     Sym "field1"
+  #     Sym "field2"
+  #     ...
+
+  if objDefAst[1].kind == nnkSym:
+    # We have a base class symbol, let's recurse and try and resolve the fields
+    # for the base class
+    for fieldDef in objDefAst[1].fields: result.add(fieldDef)
+
+  for fieldDef in objDefAst[2].children:
+    # objDefAst[2] is a RecList of
+    # ignore AST nodes that are not field definitions
+    if fieldDef.kind == nnkIdentDefs: result.add((fieldDef[0], fieldDef[1]))
+    elif fieldDef.kind == nnkSym: result.add((fieldDef, fieldDef.getTypeInst))
+    else: error "unknown object field definition AST: $#" % $fieldDef.kind
+
 template walkFieldDefs*(t: NimNode, body: untyped) =
   ## Iterate over every field of the given Nim object, yielding and defining
   ## `fieldIdent` and `fieldType`, the name of the field as a Nim Ident node
   ## and the type of the field as a Nim Type node respectively.
-  let tTypeImpl = t.getTypeImpl
+  for (fieldIdent {.inject.}, fieldType {.inject.}) in t.fields: body
 
-  var nodeToItr: NimNode
-  if tTypeImpl.typeKind == ntyObject: nodeToItr = tTypeImpl[2]
-  elif tTypeImpl.typeKind == ntyTypeDesc: nodeToItr = tTypeImpl.getType[1].getType[2]
-  else: error $t & " is not an object or type desc (it's a " & $tTypeImpl.typeKind & ")."
-
-  for fieldDef {.inject.} in nodeToItr.children:
-    # ignore AST nodes that are not field definitions
-    if fieldDef.kind == nnkIdentDefs:
-      let fieldIdent {.inject.} = fieldDef[0]
-      let fieldType {.inject.} = fieldDef[1]
-      body
-
-    elif fieldDef.kind == nnkSym:
-      let fieldIdent {.inject.} = fieldDef
-      let fieldType {.inject.} = fieldDef.getType
-      body
+#[ TODO: replace walkFieldDefs with things like this:
+func columnNamesForModel*(modelType: typedesc): seq[string] =
+  modelType.fields.mapIt(identNameToDb($it[0]))
+]#
 
 macro columnNamesForModel*(modelType: typed): seq[string] =
   ## Return the column names corresponding to the the fields of the given
@@ -317,6 +374,7 @@ macro rowToModel*(modelType: typed, row: seq[string]): untyped =
       createParseStmt(fieldType, itemLookup)))
     idx += 1
 
+#[
 macro listFields*(t: typed): untyped =
   var fields: seq[tuple[n: string, t: string]] = @[]
   t.walkFieldDefs:
@@ -324,6 +382,7 @@ macro listFields*(t: typed): untyped =
     else: fields.add((n: $fieldIdent, t: $fieldType))
 
   result = newLit(fields)
+]#
 
 proc typeOfColumn*(modelType: NimNode, colName: string): NimNode =
   ## Given a model type and a column name, return the Nim type for that column.