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Configs: use a uniform syntax without Match exceptions (#507)

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* Configs: use a uniform syntax without Match exceptions

The old style of specifying Configs used total functions.  The only way to
indicate that a key was not matched was to throw an exception.  Not only was
this a performance concern, but it also caused confusing error messages
whenever you had a match failure from a lookup within a lookup.  The
exception could get handled by an outer-lookup that then reported the wrong
key as missing.
This commit is contained in:
Wesley W. Terpstra
2017-01-13 14:41:19 -08:00
committed by Henry Cook
parent b448387899
commit 52bb6cd9d9
5 changed files with 405 additions and 549 deletions
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44
src/main/scala/config/Config.scala
View File

@ -3,9 +3,6 @@
package config
class Field[T]
class CDEMatchError() extends Exception {
override def fillInStackTrace() = this
}
abstract class View {
final def apply[T](pname: Field[T]): T = apply(pname, this)
@ -15,38 +12,28 @@ abstract class View {
}
abstract class Parameters extends View {
final def ++ (x: Parameters): Parameters = new ChainParameters(this, x)
final def alter(f: (Any, View, View, View) => Any): Parameters = Parameters(f) ++ this
final def alter(m: Map[Any,Any]): Parameters = Parameters(m) ++ this
final def alter(f: PartialFunction[Any,Any]): Parameters = Parameters(f) ++ this
final def alterPartial(f: PartialFunction[Any,Any]): Parameters = Parameters(f) ++ this
final def ++ (x: Parameters): Parameters = new ChainParameters(this, x)
final def alter(f: (View, View, View) => PartialFunction[Any,Any]): Parameters = Parameters(f) ++ this
final def alterPartial(f: PartialFunction[Any,Any]): Parameters = Parameters((_,_,_) => f) ++ this
protected[config] def chain(site: View, tail: View, pname: Any): Any
protected[config] def find(pname: Any, site: View) = chain(site, new TerminalView, pname)
}
object Parameters {
def empty: Parameters = new EmptyParameters
def apply(f: (Any, View, View, View) => Any): Parameters = new FunctionParameters(f)
def apply(m: Map[Any,Any]): Parameters = new MapParameters(m)
def apply(f: PartialFunction[Any,Any]): Parameters = new PartialParameters(f)
def partial(f: PartialFunction[Any,Any]): Parameters = new PartialParameters(f)
def empty: Parameters = new EmptyParameters
def apply(f: (View, View, View) => PartialFunction[Any,Any]): Parameters = new PartialParameters(f)
def root(p: Parameters) = p
}
class Config(p: Parameters) extends Parameters {
def this(f: (Any, View, View) => Any) = this(Parameters((p,s,h,u) => f(p,s,h))) // backwards compat; don't use
def this(f: (Any, View, View, View) => Any) = this(Parameters(f))
def this(m: Map[Any,Any]) = this(Parameters(m))
def this(f: PartialFunction[Any,Any]) = this(Parameters(f))
def this(f: (View, View, View) => PartialFunction[Any,Any]) = this(Parameters(f))
protected[config] def chain(site: View, tail: View, pname: Any) = p.chain(site, tail, pname)
override def toString = this.getClass.getSimpleName
def toInstance = this
}
class ConfigPartial(f: PartialFunction[Any,Any]) extends Config(Parameters(f))
// Internal implementation:
private class TerminalView extends View {
@ -66,22 +53,9 @@ private class EmptyParameters extends Parameters {
def chain(site: View, tail: View, pname: Any) = tail.find(pname, site)
}
private class FunctionParameters(f: (Any, View, View, View) => Any) extends Parameters {
private class PartialParameters(f: (View, View, View) => PartialFunction[Any,Any]) extends Parameters {
protected[config] def chain(site: View, tail: View, pname: Any) = {
try f(pname, site, this, tail)
catch {
case e: CDEMatchError => tail.find(pname, site)
case e: scala.MatchError => tail.find(pname, site)
}
val g = f(site, this, tail)
if (g.isDefinedAt(pname)) g.apply(pname) else tail.find(pname, site)
}
}
private class MapParameters(map: Map[Any, Any]) extends Parameters {
protected[config] def chain(site: View, tail: View, pname: Any) =
map.get(pname).getOrElse(find(pname, site))
}
private class PartialParameters(f: PartialFunction[Any,Any]) extends Parameters {
protected[config] def chain(site: View, tail: View, pname: Any) =
if (f.isDefinedAt(pname)) f.apply(pname) else tail.find(pname, site)
}