Feat: Add a blog configuration with yaml (#17214)

- Add input config, who allow to define the path import
- Add output config, who allow to define the path destination
- Add hidden, who allow to not generate the blog

Should I add warnings? For example when the path is not found. If so,
how do I test? Because the path is searched for _blog but it is not
found so the assert that asks for no warnings does not work as in [this
one](https://github.com/lampepfl/dotty/blob/d4a86000404cd3bb774025d48151c6311d6bc96d/scaladoc/test/dotty/tools/scaladoc/ReportingTest.scala#L73).

Here is my proposal to add a blog configuration using a .yaml in the
same place as the sidebar.yaml. This
[feature](#14487) request is a
bit old but I thought it would be interesting to create it to give a bit
more flexibility to Scaladoc users.
This first PR allows me to validate with you if this feature is good to
implement and also to have some feedbacks I answer well to what is asked
and that my code is relevant. So if it is the case, I will do the tests
and the associated documentation.

### TO-DO list:
- [x] First version of the code
- [x] Add documentation

Will be implemented in docs.scala-lang, [PR
#2796](scala/docs.scala-lang#2796):
***
### Blog Configuration Documentation
Blog configuration is an important aspect of any blog platform. In order
to customize the configuration of a blog, it is often necessary to
modify the default settings. In this document, we will explain how to
change the default config of a blog documentation with a file blog.yaml.

In order to modify the default settings of the blog documentation, users
need to create a file named "blog.yaml" in the root directory of the
blog. The file should contain the parameters that the user wants to
change. For example, if a user wants to change the input directory to
"my_posts", the output directory to "my_docs", and temporarily hide the
blog, they can create a file with the following content:

`blog.yaml:`
```
input: my_posts
output: my_docs
hidden: true
```
Parameters:

The blog.yaml file is a configuration file that allows users to modify
the default settings of their blog documentation. The following
parameters can be configured in the blog.yaml file:

input: This parameter specifies the directory where the markdown pages
and other files will be taken for the blogs page. By default, this is
set to the "_posts" folder in the "docs" directory of the blog. However,
users can change this to any other directory in "docs".

output: This parameter specifies the folder where the HTML pages will be
generated. By default, this is set to the "blog" folder in the
"target/docs" directory. However, users can change this to any other
directory on "target/docs".

hidden: This parameter allows users to hide or unhide the blog
temporarily. By default, this is set to "false", which means that the
blog is visible to all users. However, if a user wants to temporarily
hide the blog, they can set this parameter to "true". This can be useful
if the user wants to make some changes to the blog and doesn't want
anyone to see the changes until they are ready.

Once the file is created, the user needs to save it in the root
directory of the blog. The next time the blog is built, the new settings
will be applied.
***
- [x] Add tests

## Example (Success)

### Code & Input
<img width="328" alt="Screenshot 2023-04-06 at 14 41 47"
src="https://user-images.githubusercontent.com/44496264/230382241-9433d641-03ec-4495-8fd2-81fa6ce3bc17.png">
<img width="329" alt="Screenshot 2023-04-06 at 14 41 58"
src="https://user-images.githubusercontent.com/44496264/230382414-7876c601-b1f0-498f-85e1-71ecc500cf09.png">

### Result
<img width="326" alt="Screenshot 2023-04-06 at 14 42 09"
src="https://user-images.githubusercontent.com/44496264/230382463-9fe234ac-3fd0-4d56-a04c-6f6deb01a308.png">

## First example (Hidden)

### Code
<img width="254" alt="Screenshot 2023-04-06 at 14 46 27"
src="https://user-images.githubusercontent.com/44496264/230382770-7aabf9a2-e46f-429d-b1c9-97892072349a.png">

### Result
<img width="335" alt="Screenshot 2023-04-06 at 14 42 36"
src="https://user-images.githubusercontent.com/44496264/230383192-05e0187f-5ecf-4bd9-8697-122093577d43.png">
<img width="316" alt="Screenshot 2023-04-06 at 14 42 47"
src="https://user-images.githubusercontent.com/44496264/230382928-8130cddd-f8dd-4b43-bee1-15129af308c8.png">

## Example (Error)
<img width="316" alt="Screenshot 2023-04-06 at 14 43 03"
src="https://user-images.githubusercontent.com/44496264/230383219-ff6844e2-47c5-40d6-9056-a8ab1dc6f8e6.png">
<img width="945" alt="Screenshot 2023-04-06 at 14 43 14"
src="https://user-images.githubusercontent.com/44496264/230383236-2ee07f63-640c-4bc1-a3b1-e0785ff467e9.png">


Fixes: #14487

Author: Florian3k

scaladoc/src/dotty/tools/scaladoc/site/BlogParser.scala

@@ -0,0 +1,26 @@
+package dotty.tools.scaladoc.site
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.dataformat.yaml.YAMLFactory
+import com.fasterxml.jackson.databind.DeserializationFeature
+import java.io.File
+import scala.beans.{BooleanBeanProperty, BeanProperty}
+import scala.util.Try
+
+case class BlogConfig(
+  @BeanProperty input: String,
+  @BeanProperty output: String,
+  @BooleanBeanProperty hidden: Boolean
+):
+  def this() = this(null, null, false)
+
+object BlogParser:
+  def readYml(content: File | String): BlogConfig =
+    val mapper = ObjectMapper(YAMLFactory())
+      .findAndRegisterModules()
+
+    content match
+      case f: File =>
+        val ymlFile = f.toPath.resolve("blog.yml").toFile
+        if ymlFile.exists then mapper.readValue(ymlFile, classOf[BlogConfig]) else new BlogConfig
+      case s: String => Try(mapper.readValue(s, classOf[BlogConfig])).getOrElse(new BlogConfig)

scaladoc/src/dotty/tools/scaladoc/site/StaticSiteContext.scala

@@ -23,6 +23,10 @@ class StaticSiteContext(
   val docsPath = root.toPath.resolve("_docs")
   val blogPath = root.toPath.resolve("_blog")
 
+  def resolveNewBlogPath(stringPath: String): Path =
+    if stringPath.nonEmpty then root.toPath.resolve(stringPath)
+    else blogPath
+
   def relativize(path: Path): Path =
     if args.apiSubdirectory then
       docsPath.relativize(path)

scaladoc/src/dotty/tools/scaladoc/site/StaticSiteLoader.scala

@@ -5,6 +5,7 @@ import java.io.File
 import java.nio.file.Files
 import java.nio.file.{ Paths, Path }
 import scala.io._
+import dotty.tools.scaladoc.site.BlogParser
 
 class StaticSiteLoader(val root: File, val args: Scaladoc.Args)(using StaticSiteContext, CompilerContext):
   val ctx: StaticSiteContext = summon[StaticSiteContext]
@@ -114,10 +115,12 @@ class StaticSiteLoader(val root: File, val args: Scaladoc.Args)(using StaticSite
   }
 
   def loadBlog(): Option[LoadedTemplate] = {
+    val blogConfig = BlogParser.readYml(root)
+    val rootPath = Option(blogConfig.input).map(input => ctx.resolveNewBlogPath(input)).getOrElse(ctx.blogPath)
+    val defaultDirectory = Option(blogConfig.output).getOrElse("blog")
+
     type Date = (String, String, String)
-    val rootPath = ctx.blogPath
-    val defaultDirectory = "blog"
-    if (!Files.exists(rootPath)) None
+    if (!Files.exists(rootPath) || blogConfig.hidden) None
     else {
       val indexPageOpt = Seq(
           rootPath.resolve("index.md"),

scaladoc/test/dotty/tools/scaladoc/site/BlogParserTest.scala

@@ -0,0 +1,19 @@
+package dotty.tools.scaladoc
+package site
+
+import org.junit.Test
+import org.junit.Assert._
+
+class BlogParserTest:
+
+  private val blogConfig =
+    """input: blog
+      |output: blog
+      |hidden: false
+      |""".stripMargin
+
+  @Test
+  def loadBlog(): Unit = assertEquals(
+    BlogConfig("blog", "blog", false),
+    BlogParser.readYml(blogConfig)
+  )