Implement Html.Parser.nodeToString.

Fixes #7.

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+## [2.3.0] - 2019-03-10
+### Added
+- `Html.Parser.nodeToString` to turn parser nodes back into its HTML representation.
+
 ## [2.2.0] - 2019-02-27
 ### Added
 - Expose `Html.Parser.node` to allow other folks to build different parsers on top of this one!
@@ -38,7 +42,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 [named-character-references]: https://www.w3.org/TR/html5/syntax.html#named-character-references
 
-[Unreleased]: https://github.com/hecrj/html-parser/compare/2.2.0...HEAD
+[Unreleased]: https://github.com/hecrj/html-parser/compare/2.3.0...HEAD
+[2.3.0]: https://github.com/hecrj/html-parser/compare/2.2.0...2.3.0
 [2.2.0]: https://github.com/hecrj/html-parser/compare/2.1.0...2.2.0
 [2.1.0]: https://github.com/hecrj/html-parser/compare/2.0.1...2.1.0
 [2.0.1]: https://github.com/hecrj/html-parser/compare/2.0.0...2.0.1

elm.json

@@ -3,7 +3,7 @@
     "name": "hecrj/html-parser",
     "summary": "Parse HTML 5 in Elm",
     "license": "BSD-3-Clause",
-    "version": "2.2.0",
+    "version": "2.3.0",
     "exposed-modules": [
         "Html.Parser",
         "Html.Parser.Util"

src/Html/Parser.elm

@@ -1,6 +1,6 @@
 module Html.Parser exposing
     ( run, Node(..), Attribute
-    , node
+    , node, nodeToString
     )
 
 {-| Parse HTML 5 in Elm.
@@ -9,14 +9,14 @@ See <https://www.w3.org/TR/html5/syntax.html>
 @docs run, Node, Attribute
 
 
-# Parser internals
+# Internals
 
 If you are building a parser of your own using [`elm/parser`][elm-parser] and
 you need to parse HTML... This section is for you!
 
 [elm-parser]: https://package.elm-lang.org/packages/elm/parser/latest
 
-@docs node
+@docs node, nodeToString
 
 -}
 
@@ -67,7 +67,7 @@ type alias Attribute =
     ( String, String )
 
 
-{-| Parses an HTML node.
+{-| Parse an HTML node.
 
 You can use this in your own parser to add support for HTML 5.
 
@@ -81,6 +81,62 @@ node =
         ]
 
 
+{-| Turn a parser node back into its HTML string.
+
+For instance:
+
+    Element "a"
+        [ ( "href", "https://elm-lang.org" ) ]
+        [ Text "Elm" ]
+        |> toString
+
+Produces `<a href="https://elm-lang.org">Elm</a>`.
+
+-}
+nodeToString : Node -> String
+nodeToString node_ =
+    let
+        attributeToString ( attr, value ) =
+            attr ++ "=\"" ++ value ++ "\""
+    in
+    case node_ of
+        Text text_ ->
+            text_
+
+        Element name attributes children ->
+            let
+                maybeAttributes =
+                    case attributes of
+                        [] ->
+                            ""
+
+                        _ ->
+                            " " ++ String.join "" (List.map attributeToString attributes)
+            in
+            if isVoidElement name then
+                String.concat
+                    [ "<"
+                    , name
+                    , maybeAttributes
+                    , ">"
+                    ]
+
+            else
+                String.concat
+                    [ "<"
+                    , name
+                    , maybeAttributes
+                    , ">"
+                    , String.join "" (List.map nodeToString children)
+                    , "</"
+                    , name
+                    , ">"
+                    ]
+
+        Comment comment_ ->
+            "<!-- " ++ comment_ ++ " -->"
+
+
 
 -- Text
 

tests/Main.elm

@@ -91,6 +91,41 @@ nodeTests =
         ]
 
 
+nodeToStringTests : Test
+nodeToStringTests =
+    describe "nodeToString"
+        [ test "simple link" <|
+            \_ ->
+                Element "a" [ ( "href", "https://elm-lang.org" ) ] [ Text "Elm" ]
+                    |> Html.Parser.nodeToString
+                    |> Expect.equal "<a href=\"https://elm-lang.org\">Elm</a>"
+        , test "container" <|
+            \_ ->
+                Element "div"
+                    []
+                    [ Element "p" [] [ Text "Hello," ]
+                    , Element "p" [] [ Text "World!" ]
+                    ]
+                    |> Html.Parser.nodeToString
+                    |> Expect.equal "<div><p>Hello,</p><p>World!</p></div>"
+        , test "void element" <|
+            \_ ->
+                Element "br" [] [ Element "a" [] [ Text "should be ignored" ] ]
+                    |> Html.Parser.nodeToString
+                    |> Expect.equal "<br>"
+        , test "comment" <|
+            \_ ->
+                Comment "This is a comment"
+                    |> Html.Parser.nodeToString
+                    |> Expect.equal "<!-- This is a comment -->"
+        , test "text" <|
+            \_ ->
+                Text "Hello, world!"
+                    |> Html.Parser.nodeToString
+                    |> Expect.equal "Hello, world!"
+        ]
+
+
 scriptTests : Test
 scriptTests =
     describe "Script"
@@ -148,6 +183,7 @@ suite =
     describe "HtmlParser"
         [ textNodeTests
         , nodeTests
+        , nodeToStringTests
         , commentTests
         , attributeTests
         , errorTests