[ISSUE-296] Add support for fish autocompletions

modules/cli/src/main/scala/scala/cli/commands/installcompletions/InstallCompletions.scala

@@ -1,7 +1,7 @@
 package scala.cli.commands.installcompletions
 
 import caseapp.*
-import caseapp.core.complete.{Bash, Zsh}
+import caseapp.core.complete.{Bash, Fish, Zsh}
 import caseapp.core.help.HelpFormat
 
 import java.io.File
@@ -47,6 +47,7 @@ object InstallCompletions extends ScalaCommand[InstallCompletionsOptions] {
         )
         System.err.println(s"$name install completions --shell zsh")
         System.err.println(s"$name install completions --shell bash")
+        System.err.println(s"$name install completions --shell fish")
         sys.exit(1)
       }
     }
@@ -76,6 +77,10 @@ object InstallCompletions extends ScalaCommand[InstallCompletionsOptions] {
           "compinit"
         ).map(_ + System.lineSeparator()).mkString
         (script, defaultRcFile)
+      case Fish.id | "fish" =>
+        val script        = Fish.script(name)
+        val defaultRcFile = os.home / ".config" / "fish" / "config.fish"
+        (script, defaultRcFile)
       case _ =>
         System.err.println(s"Unrecognized or unsupported shell: $format")
         sys.exit(1)
@@ -118,6 +123,7 @@ object InstallCompletions extends ScalaCommand[InstallCompletionsOptions] {
         EnvVar.Misc.shell.valueOpt.map(_.split("[\\/]+").last).map {
           case "bash" => Bash.id
           case "zsh"  => Zsh.id
+          case "fish" => Fish.id
           case other  => other
         }
       }

modules/cli/src/main/scala/scala/cli/commands/uninstallcompletions/UninstallCompletions.scala

@@ -37,7 +37,8 @@ object UninstallCompletions extends ScalaCommand[UninstallCompletionsOptions] {
       .getOrElse(os.home)
     val rcFiles = options.shared.rcFile.map(file => Seq(os.Path(file, os.pwd))).getOrElse(Seq(
       zDotDir / ".zshrc",
-      os.home / ".bashrc"
+      os.home / ".bashrc",
+      os.home / ".config" / "fish" / "config.fish"
     )).filter(os.exists(_))
 
     rcFiles.foreach { rcFile =>

modules/integration/src/test/scala/scala/cli/integration/InstallAndUninstallCompletionsTests.scala

@@ -8,32 +8,41 @@ import scala.util.Properties
 class InstallAndUninstallCompletionsTests extends ScalaCliSuite {
   val zshRcFile: String  = ".zshrc"
   val bashRcFile: String = ".bashrc"
+  val fishRcFile: String = "config.fish"
   val rcContent: String = s"""
                              |dummy line
                              |dummy line""".stripMargin
   val testInputs: TestInputs = TestInputs(
-    os.rel / zshRcFile  -> rcContent,
-    os.rel / bashRcFile -> rcContent
+    os.rel / zshRcFile                       -> rcContent,
+    os.rel / bashRcFile                      -> rcContent,
+    os.rel / ".config" / "fish" / fishRcFile -> rcContent
   )
 
   def runInstallAndUninstallCompletions(): Unit = {
     testInputs.fromRoot { root =>
       val zshRcPath  = root / zshRcFile
       val bashRcPath = root / bashRcFile
+      val fishRcPath = root / ".config" / "fish" / fishRcFile
       // install completions to the dummy rc files
       os.proc(TestUtil.cli, "install-completions", "--rc-file", zshRcPath, "--shell", "zsh").call(
         cwd = root
       )
       os.proc(TestUtil.cli, "install-completions", "--rc-file", bashRcPath, "--shell", "bash").call(
         cwd = root
       )
+      os.proc(TestUtil.cli, "install-completions", "--rc-file", fishRcPath, "--shell", "fish").call(
+        cwd = root
+      )
       expect(os.read(bashRcPath).contains(bashRcScript))
       expect(os.read(zshRcPath).contains(zshRcScript))
+      expect(os.read(fishRcPath).contains(fishRcScript))
       // uninstall completions from the dummy rc files
       os.proc(TestUtil.cli, "uninstall-completions", "--rc-file", zshRcPath).call(cwd = root)
       os.proc(TestUtil.cli, "uninstall-completions", "--rc-file", bashRcPath).call(cwd = root)
+      os.proc(TestUtil.cli, "uninstall-completions", "--rc-file", fishRcPath).call(cwd = root)
       expect(os.read(zshRcPath) == rcContent)
       expect(os.read(bashRcPath) == rcContent)
+      expect(os.read(fishRcPath) == rcContent)
     }
   }
 
@@ -57,6 +66,15 @@ class InstallAndUninstallCompletionsTests extends ScalaCliSuite {
     addTags(script)
   }
 
+  lazy val fishRcScript: String = {
+    val progName = "scala-cli"
+    val script =
+      s"""
+    complete $progName -a '($progName complete fish-v1 (math 1 + (count (__fish_print_cmd_args))) (__fish_print_cmd_args))'
+         |""".stripMargin
+    addTags(script)
+  }
+
   lazy val zshRcScript: String = {
     val projDirs = ProjectDirectories.from(null, null, "ScalaCli")
     val dir      = os.Path(projDirs.dataLocalDir, TestUtil.pwd) / "completions" / "zsh"

website/docs/_advanced_install.mdx

@@ -447,9 +447,11 @@ Alternatively, you can directly download it from the Maven repository [here](htt
         values={[
         {label: 'Bash', value: 'bash'},
         {label: 'zsh', value: 'zsh'},
+        {label: 'fish', value: 'fish'},
         ]}>
      <TabItem value="bash"></TabItem>
      <TabItem value="zsh"></TabItem>
+     <TabItem value="fish"></TabItem>
     </Tabs>
 </SectionAbout>
 
@@ -463,6 +465,7 @@ Try the completions with
       values={[
         {label: 'Bash', value: 'bash'},
         {label: 'zsh', value: 'zsh'},
+        {label: 'fish', value: 'fish'},
         ]}>
 <TabItem value="bash">
 
@@ -479,6 +482,15 @@ eval "$(scala-cli install completions --env --shell zsh)"
 scala-cli --<TAB>
 ```
 
+</TabItem>
+<TabItem value="fish">
+
+```
+eval "$(scala-cli install completions --env --shell fish)"
+fish
+scala-cli --<TAB>
+```
+
 </TabItem>
 </Tabs>
 
@@ -493,6 +505,7 @@ with `--shell`
       values={[
         {label: 'Bash', value: 'bash'},
         {label: 'zsh', value: 'zsh'},
+        {label: 'fish', value: 'fish'},
         ]}>
 <TabItem value="bash">
 
@@ -507,6 +520,13 @@ scala-cli install completions --shell bash
 scala-cli install completions --shell zsh
 ```
 
+</TabItem>
+<TabItem value="fish">
+
+```bash
+scala-cli install completions --shell fish
+```
+
 </TabItem>
 </Tabs>
 </div></div>