Add the ability to trace the provenance of config values.

cliutils.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "0.11.1"
+version       = "0.12.0"
 author        = "Jonathan Bernard"
 description   = "Helper functions for writing command line interfaces."
 license       = "MIT"
@@ -8,4 +8,4 @@ license       = "MIT"
 
 # Dependencies
 
-requires @["nim >= 1.6.0", "docopt >= 0.6.8"]
+requires @["nim >= 1.6.0", "docopt >= 0.6.8", "regex", "identcasing"]

cliutils/config.nim

@@ -1,19 +1,56 @@
-import std/[json, nre, os, sequtils, strtabs, strutils]
-import docopt
+import std/[json, os, sequtils, strtabs, strutils]
+import docopt, identcasing, regex
 
 type
   CombinedConfig* = object
     docopt*: Table[string, Value]
     json*: JsonNode
 
-proc keyNames(key: string): tuple[arg, env, json: string] {.raises: [KeyError].} =
+  ValueProvenance* {.pure.} = enum arguments, environment, json, default
+
+const argStyleRegex = re2"(--)?[[:lower:][:digit:]][[:lower:][:digit:]\-]+"
+const envStyleRegex = re2"[[:upper:][:digit:]_]+"
+const jsonStyleRegex = re2"[[:lower:]][[:lower:][:upper:][:digit:]]+"
+
+proc keyNames*(key: string): tuple[arg, env, json: string]
+    {.raises: [KeyError].} =
+  ## CombinedConfig tries to be idiomatic in its usage of key names. For
+  ## environment variables it uses `UPPER_SNAKE_CASE`-style naming. For
+  ## arguments it uses `lower-kebab-case`, and for JSON it uses
+  ## `lowerCamelCase`.
+  ##
+  ## *keyNames* takes a key in any one of the three styles and returns all
+  ## three. This is primarily a helper for other parsing functions, but is
+  ## exposed as it is sometimes useful.
   try:
-    result = (
-      "--" & key,
-      key.replace('-', '_').toUpper,
-      key.replace(re"(-\w)", proc (m: RegexMatch): string = ($m)[1..1].toUpper))
+    if match(key, argStyleRegex):
+      let unprefixed =
+        if key.startsWith("--"): key[2..^1]
+        else: key
+
+      return (
+        "--" & unprefixed,
+        convertCase(unprefixed, lowerKebabCase, upperSnakeCase),
+        convertCase(unprefixed, lowerKebabCase, lowerCamelCase))
+
+    elif match(key, envStyleRegex):
+      return (
+        "--" & convertCase(key, upperSnakeCase, lowerKebabCase),
+        key,
+        convertCase(key, upperSnakeCase, lowerCamelCase))
+
+    elif match(key, jsonStyleRegex):
+      return (
+        "--" & convertCase(key, lowerCamelCase, lowerKebabCase),
+        convertCase(key, lowerCamelCase, upperSnakeCase),
+        key)
+
+    else: raise newException(KeyError,
+      "key style must be --argument-style, ENV_STYLE, or jsonStyle")
   except Exception:
-    raise newException(KeyError, "invalid config key: '" & key & "'")
+    raise newException(KeyError, "invalid config key '" & key & "': " &
+      getCurrentExceptionMsg())
+
 
 template walkFieldDefs*(t: NimNode, body: untyped) =
   let tTypeImpl = t.getTypeImpl
@@ -51,6 +88,7 @@ proc initCombinedConfig*(
 
   result = CombinedConfig(docopt: docopt, json: parseFile(filename))
 
+
 proc findConfigFile*(name: string, otherLocations: seq[string] = @[]): string =
   let cfgLocations = @[
     $getEnv(name.strip(chars = {'.'}).toUpper()),
@@ -61,42 +99,88 @@ proc findConfigFile*(name: string, otherLocations: seq[string] = @[]): string =
   if result == "" or not fileExists(result):
     raise newException(ValueError, "could not find configuration file")
 
-proc getVal*(cfg: CombinedConfig, key: string): string =
+
+proc getValueAndProvenance*(
+    cfg: CombinedConfig,
+    key: string): tuple[value: string, provenance: ValueProvenance]
+    {. raises: [ValueError] .} =
   let (argKey, envKey, jsonKey) = keyNames(key)
 
-  if cfg.docopt.contains(argKey) and cfg.docopt[argKey]: return $cfg.docopt[argKey]
-  elif existsEnv(envKey): return getEnv(envKey)
+  if cfg.docopt.contains(argKey) and cfg.docopt[argKey]:
+    return ($cfg.docopt[argKey], ValueProvenance.arguments)
+  elif existsEnv(envKey):
+    return (getEnv(envKey), ValueProvenance.environment)
   elif cfg.json.hasKey(jsonKey):
     let node = cfg.json[jsonKey]
-    case node.kind
-    of JString: return node.getStr
-    of JInt: return $node.getInt
-    of JFloat: return $node.getFloat
-    of JBool: return $node.getBool
-    of JNull: return ""
-    of JObject: return $node
-    of JArray: return $node
+    let value =
+      case node.kind
+      of JString: node.getStr
+      of JInt: $node.getInt
+      of JFloat: $node.getFloat
+      of JBool: $node.getBool
+      of JNull: ""
+      of JObject: $node
+      of JArray: $node
+    return (value, ValueProvenance.json)
   else: raise newException(ValueError, "cannot find a configuration value for \"" & key & "\"")
 
+
+proc getValueAndProvenance*(
+    cfg: CombinedConfig,
+    key: string,
+    default: string): tuple[value: string, provenance: ValueProvenance]
+    {.raises: [].} =
+  try: return getValueAndProvenance(cfg, key)
+  except CatchableError: return (default, ValueProvenance.default)
+
+
+proc getVal*(cfg: CombinedConfig, key: string): string =
+  getValueAndProvenance(cfg, key).value
+
+
 proc getVal*(cfg: CombinedConfig, key, default: string): string {.raises: [].} =
   try: return getVal(cfg, key)
   except CatchableError: return default
 
-proc getJson*(
+
+proc `[]`*(cfg: CombinedConfig, key: string): string = getVal(cfg, key)
+
+
+proc getJsonValueAndProvenance*(
     cfg: CombinedConfig,
-    key: string
-  ): JsonNode {.raises: [KeyError, ValueError, IOError, OSError]} =
+    key: string): tuple[value: JsonNode, provenance: ValueProvenance]
+    {.raises: [KeyError, ValueError, IOError, OSError]} =
 
   let (argKey, envKey, jsonKey) = keyNames(key)
 
   try:
-    if cfg.docopt.contains(argKey) and cfg.docopt[argKey]: return parseJson($cfg.docopt[argKey])
-    elif existsEnv(envKey): return parseJson(getEnv(envKey))
-    elif cfg.json.hasKey(jsonKey): return cfg.json[jsonKey]
+    if cfg.docopt.contains(argKey) and cfg.docopt[argKey]:
+      return (parseJson($cfg.docopt[argKey]), ValueProvenance.arguments)
+    elif existsEnv(envKey):
+      return (parseJson(getEnv(envKey)), ValueProvenance.environment)
+    elif cfg.json.hasKey(jsonKey):
+      return (cfg.json[jsonKey], ValueProvenance.json)
     else: raise newException(ValueError, "cannot find a configuration value for \"" & key & "\"")
   except Exception:
     raise newException(ValueError, "cannot parse [" & getVal(cfg, key) & "] as JSON:" & getCurrentExceptionMsg())
 
+
+proc getJsonValueAndProvenance*(
+    cfg: CombinedConfig,
+    key: string,
+    default: JsonNode): tuple[value: JsonNode, provenance: ValueProvenance]
+    {.raises: [].} =
+  try: return getJsonValueAndProvenance(cfg, key)
+  except CatchableError: return (default, ValueProvenance.default)
+
+
+proc getJson*(
+    cfg: CombinedConfig,
+    key: string
+  ): JsonNode {.raises: [KeyError, ValueError, IOError, OSError]} =
+  getJsonValueAndProvenance(cfg, key).value
+
+
 proc getJson*(
     cfg: CombinedConfig,
     key: string,
@@ -106,6 +190,7 @@ proc getJson*(
   try: return getJson(cfg, key)
   except CatchableError: return default
 
+
 proc hasKey*(cfg: CombinedConfig, key: string): bool =
   let (argKey, envKey, jsonKey) = keyNames(key)
 
@@ -114,6 +199,10 @@ proc hasKey*(cfg: CombinedConfig, key: string): bool =
     existsEnv(envKey) or
     cfg.json.hasKey(jsonKey)
 
+
+proc contains*(cfg: CombinedConfig, key: string): bool = hasKey(cfg, key)
+
+
 proc loadEnv*(): StringTableRef =
   result = newStringTable()