Add error handling.

db_migrate.nim

@@ -8,22 +8,16 @@ import json, times, os, docopt
 type DbMigrateConfig* = tuple[ driver, sqlDir, connectionString: string ]
 
 proc loadConfig*(filename: string): DbMigrateConfig =
+  ## Load DbMigrateConfig from a file. 
   let cfg = json.parseFile(filename)
-  let config = (
+
+  return (
     driver: if cfg.hasKey("driver"): cfg["driver"].getStr else: "postres",
     sqlDir: if cfg.hasKey("sqlDir"): cfg["sqlDir"].getStr else: "migrations",
     connectionString: cfg["connectionString"].getStr)
 
-  # Check for migrations directory
-  # TODO: try/except
-  if not existsDir config.sqlDir:
-    echo "SQL directory '" & config.sqlDir &
-      "' does not exist and will be created."
-    createDir config.sqlDir
-
-  return config
-
 proc createMigration*(config: DBMigrateConfig, migrationName: string): seq[string] =
+  ## Create a new set of database migration files.
   let timestamp = getTime().getLocalTime().format("yyyyMMddHHmmss")
   let filenamePrefix =  timestamp & "-" & migrationName
 
@@ -32,7 +26,6 @@ proc createMigration*(config: DBMigrateConfig, migrationName: string): seq[strin
 
   let scriptDesc = migrationName & " (" & timestamp & ")"
 
-  # TODO: try/except and catch errors creating files.
   let upFile = open(upFilename, fmWrite)
   let downFile = open(downFilename, fmWrite)
 
@@ -57,17 +50,39 @@ Options:
   # Parse arguments
   let args = docopt(doc, version = "db-migrate 0.1.0")
 
-  echo $args
+  let exitErr = proc(msg: string): void = 
+    stderr.writeLine("db_migrate: " & msg)
+    quit(QuitFailure)
+
 
   # Load configuration file
   let configFilename =
     if args["--config"]: $args["--config"]
     else: "database.json"
 
-  let config = loadConfig(configFilename)
+  var config: DbMigrateConfig
+  try:
+    config = loadConfig(configFilename)
+  except IOError:
+    exitErr "Cannot open config file: " & configFilename
+  except:
+    exitErr "Error parsing config file: " & configFilename & "\L\t" & getCurrentExceptionMsg()
+
+  # Check for migrations directory
+  if not existsDir config.sqlDir:
+    try:
+      echo "SQL directory '" & config.sqlDir &
+      "' does not exist and will be created."
+      createDir config.sqlDir
+    except IOError:
+      exitErr "Unable to create directory: " & config.sqlDir & ":\L\T" & getCurrentExceptionMsg()
 
   # Execute commands
   if args["create"]:
-    let filesCreated = createMigration(config, $args["<migration-name>"])
+    try:
-    echo "Created new migration files:"
+      let filesCreated = createMigration(config, $args["<migration-name>"])
-    for filename in filesCreated: echo "\t" & filename
+      echo "Created new migration files:"
+      for filename in filesCreated: echo "\t" & filename
+    except IOError:
+      exitErr "Unable to create migration scripts: " & getCurrentExceptionMsg()
+