From 733ee44749811e3bb1cffb982d9c816dcdd1b996 Mon Sep 17 00:00:00 2001
From: Marcel Otto <marcelotto@gmx.de>
Date: Wed, 14 Mar 2018 11:46:11 +0100
Subject: [PATCH] Add RDF.Literal.new!/2

---
 CHANGELOG.md       | 10 ++++++++--
 README.md          |  5 +++--
 lib/rdf/inspect.ex | 16 +++++++++++-----
 lib/rdf/literal.ex | 39 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a322c91..17fdcf9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,10 +7,16 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 
 ## Unreleased
 
+### Added
+
+- `RDF.Literal.new!/2` which fails when creating an invalid literal 
+
+
 ### Changed
 
-- `Literal.new/2` can create `rdf:langString` literals without failing, they are 
-  simply invalid
+- `RDF.Literal.new/2` can create `rdf:langString` literals without failing, they  
+  are simply invalid; if you want to fail without a language tag use the new 
+  `RDF.Literal.new!/2` function
 
 
 [Compare v0.4.0...HEAD](https://github.com/marcelotto/rdf-ex/compare/v0.4.0...HEAD)
diff --git a/README.md b/README.md
index 3d15380..d8ff615 100644
--- a/README.md
+++ b/README.md
@@ -349,6 +349,8 @@ iex> RDF.Literal.valid? RDF.Integer.new("foo")
 false
 ```
 
+If you want to prohibit the creation of invalid literals, you can use the `new!` constructor function of `RDF.Datatype` or `RDF.Literal`, which will fail in case of invalid values.
+
 A RDF literal is bound to the lexical form of the initially given value. This lexical representation can be retrieved with the `RDF.Literal.lexical/1` function:
 
 ```elixir
@@ -706,8 +708,7 @@ Note: The later command requires the `json_ld` package to be defined as a depend
 The file read and write functions are also able to infer the format from the file extension of the given filename.
 
 ```elixir
-"/path/to/some_file.ttl"
-|> RDF.read_file!()
+RDF.read_file!("/path/to/some_file.ttl")
 |> RDF.write_file!("/path/to/some_file.jsonld")
 ```
 
diff --git a/lib/rdf/inspect.ex b/lib/rdf/inspect.ex
index e36a8f4..cbb5e48 100644
--- a/lib/rdf/inspect.ex
+++ b/lib/rdf/inspect.ex
@@ -48,6 +48,9 @@ defimpl Inspect, for: RDF.BlankNode do
 end
 
 defimpl Inspect, for: RDF.Literal do
+  @xsd_string RDF.Datatype.NS.XSD.string
+  @rdf_lang_string RDF.langString
+
   def inspect(%RDF.Literal{value: value, language: language}, _opts) when not is_nil(language) do
     ~s[~L"#{value}"#{language}]
   end
@@ -57,11 +60,14 @@ defimpl Inspect, for: RDF.Literal do
     "%RDF.Literal{value: #{inspect value}, lexical: #{inspect lexical}, datatype: ~I<#{datatype}>}"
   end
 
-  def inspect(%RDF.Literal{value: value, datatype: datatype}, _opts) do
-    if datatype == RDF.Datatype.NS.XSD.string do
-      ~s[~L"#{value}"]
-    else
-      "%RDF.Literal{value: #{inspect value}, datatype: ~I<#{datatype}>}"
+  def inspect(%RDF.Literal{value: value, datatype: datatype, language: language}, _opts) do
+    case datatype do
+      @xsd_string ->
+        ~s[~L"#{value}"]
+      @rdf_lang_string ->
+        "%RDF.Literal{value: #{inspect value}, datatype: ~I<#{datatype}>, language: #{inspect language}}"
+      _ ->
+        "%RDF.Literal{value: #{inspect value}, datatype: ~I<#{datatype}>}"
     end
   end
 end
diff --git a/lib/rdf/literal.ex b/lib/rdf/literal.ex
index 12f96e2..529dd24 100644
--- a/lib/rdf/literal.ex
+++ b/lib/rdf/literal.ex
@@ -59,6 +59,11 @@ defmodule RDF.Literal do
     raise RDF.Literal.InvalidError, "#{inspect value} not convertible to a RDF.Literal"
   end
 
+  @doc """
+  Creates a new `RDF.Literal` with the given datatype or language tag.
+  """
+  def new(value, opts)
+
   def new(value, opts) when is_list(opts),
     do: new(value, Map.new(opts))
 
@@ -88,6 +93,40 @@ defmodule RDF.Literal do
     do: new(value)
 
 
+  @doc """
+  Creates a new `RDF.Literal`, but fails if it's not valid.
+
+  Note: Validation is only possible if an `RDF.Datatype` with an implementation of
+    `RDF.Datatype.valid?/1` exists.
+
+  ## Examples
+
+      iex> RDF.Literal.new!("3.14", datatype: XSD.double) == RDF.Literal.new("3.14", datatype: XSD.double)
+      true
+
+      iex> RDF.Literal.new!("invalid", datatype: "http://example/unkown_datatype") == RDF.Literal.new("invalid", datatype: "http://example/unkown_datatype")
+      true
+
+      iex> RDF.Literal.new!("foo", datatype: XSD.integer)
+      ** (RDF.Literal.InvalidError) invalid RDF.Literal: %RDF.Literal{value: nil, lexical: "foo", datatype: ~I<http://www.w3.org/2001/XMLSchema#integer>}
+
+      iex> RDF.Literal.new!("foo", datatype: RDF.langString)
+      ** (RDF.Literal.InvalidError) invalid RDF.Literal: %RDF.Literal{value: "foo", datatype: ~I<http://www.w3.org/1999/02/22-rdf-syntax-ns#langString>, language: nil}
+
+  """
+  def new!(value, opts \\ %{}) do
+    with %RDF.Literal{} = literal <- new(value, opts) do
+      if valid?(literal) do
+        literal
+      else
+        raise RDF.Literal.InvalidError, "invalid RDF.Literal: #{inspect literal}"
+      end
+    else
+      invalid ->
+        raise RDF.Literal.InvalidError, "invalid result of RDF.Literal.new: #{inspect invalid}"
+    end
+  end
+
   @doc """
   Returns the given literal with the canonical lexical representation according to its datatype.
   """