Add fish shell completions support

core/jvm/src/main/scala/caseapp/core/app/PlatformCommandsMethods.scala

@@ -1,6 +1,6 @@
 package caseapp.core.app
 
-import caseapp.core.complete.{Bash, Zsh}
+import caseapp.core.complete.{Bash, Fish, Zsh}
 
 import java.io.File
 import java.nio.charset.{Charset, StandardCharsets}
@@ -32,14 +32,11 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
         toStderr = true
       )
       printLine("", toStderr = true)
-      printLine(
-        s"  $name ${completionsCommandName.mkString(" ")} install --shell zsh",
-        toStderr = true
-      )
-      printLine(
-        s"  $name ${completionsCommandName.mkString(" ")} install --shell bash",
-        toStderr = true
-      )
+      for (shell <- Seq(Bash.shellName, Zsh.shellName, Fish.shellName))
+        printLine(
+          s"  $name ${completionsCommandName.mkString(" ")} install --shell $shell",
+          toStderr = true
+        )
       printLine("", toStderr = true)
       exit(1)
     }
@@ -49,6 +46,15 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
         val script        = Bash.script(name)
         val defaultRcFile = Paths.get(sys.props("user.home")).resolve(".bashrc")
         (script, defaultRcFile)
+      case Fish.id | Fish.shellName =>
+        val script = Fish.script(name)
+        val defaultRcFile =
+          Option(System.getenv("XDG_CONFIG_HOME")).map(Paths.get(_))
+            .getOrElse(Paths.get(sys.props("user.home"), ".config"))
+            .resolve("fish")
+            .resolve("completions")
+            .resolve(s"$name.fish")
+        (script, defaultRcFile)
       case Zsh.id | Zsh.shellName =>
         val completionScript = Zsh.script(name)
         val zDotDir = Paths.get(Option(System.getenv("ZDOTDIR")).getOrElse(sys.props("user.home")))
@@ -69,14 +75,19 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
         ).map(_ + System.lineSeparator()).mkString
         (script, defaultRcFile)
       case _ =>
-        printLine(s"Unrecognized or unsupported shell: $format")
+        printLine(s"Unrecognized or unsupported shell: $format", toStderr = true)
         exit(1)
     }
 
     if (options.env)
       println(rcScript)
     else {
-      val rcFile = options.rcFile.map(Paths.get(_)).getOrElse(defaultRcFile)
+      val rcFile = format match {
+        case Fish.id | Fish.shellName =>
+          options.output.map(Paths.get(_, s"$name.fish")).getOrElse(defaultRcFile)
+        case _ =>
+          options.rcFile.map(Paths.get(_)).getOrElse(defaultRcFile)
+      }
       val banner = options.banner.replace("{NAME}", name)
       val updated = ProfileFileUpdater.addToProfileFile(
         rcFile,
@@ -123,9 +134,14 @@ trait PlatformCommandsMethods { self: CommandsEntryPoint =>
 
     val home    = Paths.get(sys.props("user.home"))
     val zDotDir = Option(System.getenv("ZDOTDIR")).map(Paths.get(_)).getOrElse(home)
+    val fishCompletionsDir = options.output.map(Paths.get(_))
+      .getOrElse(sys.env.get("XDG_CONFIG_HOME").map(Paths.get(_)).getOrElse(home)
+        .resolve("fish")
+        .resolve("completions"))
     val rcFiles = options.rcFile.map(file => Seq(Paths.get(file))).getOrElse(Seq(
       zDotDir.resolve(".zshrc"),
-      home.resolve(".bashrc")
+      home.resolve(".bashrc"),
+      fishCompletionsDir.resolve(s"$name.fish")
     )).filter(Files.exists(_))
 
     for (rcFile <- rcFiles) {
@@ -159,15 +175,15 @@ object PlatformCommandsMethods {
       env: Boolean = false,
     @HelpMessage("Custom completions name")
       name: Option[String] = None,
-    @HelpMessage("Name of the shell, either zsh or bash")
+    @HelpMessage("Name of the shell, either zsh, fish or bash")
     @Name("shell")
       format: Option[String] = None,
-    @HelpMessage("Completions output directory")
+    @HelpMessage("Completions output directory (defaults to $XDG_CONFIG_HOME/fish/completions on fish)")
     @Name("o")
       output: Option[String] = None,
-    @HelpMessage("Custom banner in comment placed in rc file")
+    @HelpMessage("Custom banner in comment placed in rc file (bash or zsh only)")
       banner: String = "{NAME} completions",
-    @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell")
+    @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell (bash or zsh only)")
       rcFile: Option[String] = None
   )
   // format: on
@@ -180,12 +196,15 @@ object PlatformCommandsMethods {
   // from https://github.com/VirtusLab/scala-cli/blob/eced0b35c769eca58ae6f1b1a3be0f29a8700859/modules/cli/src/main/scala/scala/cli/commands/uninstallcompletions/SharedUninstallCompletionsOptions.scala
   // format: off
   final case class CompletionsUninstallOptions(
-    @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell")
+    @HelpMessage("Path to `*rc` file, defaults to `.bashrc` or `.zshrc` depending on shell (bash or zsh only)")
       rcFile: Option[String] = None,
     @HelpMessage("Custom banner in comment placed in rc file")
       banner: String = "{NAME} completions",
     @HelpMessage("Custom completions name")
-      name: Option[String] = None
+      name: Option[String] = None,
+    @HelpMessage("Completions output directory (defaults to $XDG_CONFIG_HOME/fish/completions on fish)")
+    @Name("o")
+      output: Option[String] = None,
   )
   // format: on
 
@@ -199,6 +218,7 @@ object PlatformCommandsMethods {
       .orElse {
         Option(System.getenv("SHELL")).map(_.split(File.separator).last).map {
           case Bash.shellName => Bash.id
+          case Fish.shellName => Fish.id
           case Zsh.shellName  => Zsh.id
           case other          => other
         }

core/shared/src/main/scala/caseapp/core/app/CommandsEntryPoint.scala

@@ -1,7 +1,7 @@
 package caseapp.core.app
 
 import caseapp.core.commandparser.RuntimeCommandParser
-import caseapp.core.complete.{Bash, CompletionItem, Zsh}
+import caseapp.core.complete.{Bash, CompletionItem, Fish, Zsh}
 import caseapp.core.help.{Help, HelpFormat, RuntimeCommandHelp, RuntimeCommandsHelp}
 
 abstract class CommandsEntryPoint extends PlatformCommandsMethods {
@@ -70,6 +70,7 @@ abstract class CommandsEntryPoint extends PlatformCommandsMethods {
     def script(format: String): String =
       format match {
         case Bash.shellName | Bash.id => Bash.script(progName)
+        case Fish.shellName | Fish.id => Fish.script(progName)
         case Zsh.shellName | Zsh.id   => Zsh.script(progName)
         case _ =>
           completeUnrecognizedFormat(format)
@@ -114,6 +115,8 @@ abstract class CommandsEntryPoint extends PlatformCommandsMethods {
         format match {
           case Bash.id =>
             printLine(Bash.print(items))
+          case Fish.id =>
+            printLine(Fish.print(items))
           case Zsh.id =>
             printLine(Zsh.print(items))
           case _ =>

core/shared/src/main/scala/caseapp/core/complete/Fish.scala

@@ -0,0 +1,30 @@
+package caseapp.core.complete
+
+object Fish {
+
+  val shellName: String =
+    "fish"
+  val id: String =
+    s"$shellName-v1"
+
+  def script(progName: String): String =
+    s"""
+    complete $progName -a '($progName complete $id (math 1 + (count (__fish_print_cmd_args))) (__fish_print_cmd_args))'
+       |""".stripMargin
+
+  private def escape(s: String): String =
+    s.replace("\t", "  ").linesIterator.find(_ => true).getOrElse("")
+  def print(items: Seq[CompletionItem]): String = {
+    val newLine = System.lineSeparator()
+    val b       = new StringBuilder
+    for (item <- items; value <- item.values) {
+      b.append(escape(value))
+      for (desc <- item.description) {
+        b.append("\t")
+        b.append(escape(desc))
+      }
+      b.append(newLine)
+    }
+    b.result()
+  }
+}

project/Mima.scala

@@ -8,7 +8,7 @@ import scala.sys.process._
 object Mima {
 
   def binaryCompatibilityVersions: Set[String] =
-    Seq("git", "tag", "--merged", "HEAD^", "--contains", "8e0544e5ce1f9ce1dd3bd85308332b5dd1cd4985")
+    Seq("git", "tag", "--merged", "HEAD^", "--contains", "920fb43865d3f35c5f2c9abb5bcc91768ab9de45")
       .!!
       .linesIterator
       .map(_.trim)

tests/shared/src/test/scala/caseapp/CompletionTests.scala

@@ -1,6 +1,6 @@
 package caseapp
 
-import caseapp.core.complete.{Bash, CompletionItem, Zsh}
+import caseapp.core.complete.{Bash, CompletionItem, Fish, Zsh}
 import utest._
 
 object CompletionTests extends TestSuite {
@@ -155,6 +155,13 @@ object CompletionTests extends TestSuite {
 
         assert(compRely.contains(expectedCompRely))
       }
+      test("fish") {
+        val res              = Prog.complete(Seq("back-tick", "-"), 1)
+        val compRely         = Fish.print(res)
+        val expectedCompRely = "--backtick\tA pattern with backtick `--`\n".stripMargin
+
+        assert(compRely.contains(expectedCompRely))
+      }
       test("zsh") {
         val res = Prog.complete(Seq("back-tick", "-"), 1)
         val expected = List(