Twirl support in metals #7751

ajafri2001 · 2025-08-27T06:43:30Z

LSP support for Play Framework's Twirl Files.

This work was done as part of Google Summer of Code 2025. The last commit as of 1st September 2025 is this.

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Add twirl support

tgodzik

Thanks for the great work! There is some improvements here to do, but this will already be a great start if anyone wants to add further features.

tgodzik · 2025-09-04T12:02:28Z

metals/src/main/scala/scala/meta/internal/metals/BuildTargets.scala

+      // A bit suspicious o_O
+      if (source.toNIO.toString.isTwirlTemplate) {
+        return inverseSources(
+          source.parent.resolveSibling(_ => "scala").resolve("foo.scala")


This should be removed

Done! This is removed, although sbt-twirl doesn't provide a build-target by itself unlike play project, so people who want to use standalone twirl would get No Build Target Found. Although I'm not really sure how this all works 😅 so take this with a grain of salt 🧂

We can fix that later then.

tgodzik · 2025-09-08T07:56:45Z

metals/src/main/scala/scala/meta/internal/metals/Diagnostics.scala

-      path,
-      diagnostics.getOrElse(path, new ju.LinkedList[DiagnosticWithOrigin]()),
-    )
+    if (!path.isTwirlTemplate) {


I think we do want to publish those diagnotics from the build server. We should instead change the didChange method in Trees to:
case Some(parsed) if !path.isTwirlTemplate =>

Oh good point.

tgodzik · 2025-09-08T07:58:40Z

metals/src/main/scala/scala/meta/internal/metals/TwirlAdjustments.scala

+    }
+  }
+
+  def isPlayProject(implicit file: VirtualFile): Boolean =


AS an improvement, we could check in sbt project for play specific libraries. But this seems good enough for now.

That does make sense.

tgodzik · 2025-09-08T08:02:14Z

mtags/src/main/scala-2/scala/meta/internal/pc/AutoImportsProvider.scala

+
+            println("This is edits -> " + edits)
+


Suggested change

println("This is edits -> " + edits)

lol how did this get through 😅

tgodzik · 2025-09-09T09:55:48Z

metals/src/main/scala/scala/meta/internal/metals/Compilers.scala

+          if (locations.asScala.forall(loc => originalUri.equals(loc.getUri())))
+            adjust.adjustLocations(locations)


Suggested change

if (locations.asScala.forall(loc => originalUri.equals(loc.getUri())))

adjust.adjustLocations(locations)

val adjustable = locations.asScala.filter(loc => originalUri.toString == (loc.getUri()))

adjust.adjustLocations(adjustable)

two issue here, we:

equals didn't work because originalUri is an Uri, so different classes will never equal

there might be a rare scenarion with go to definition that it will return multiple locations (probably not in twirl, but other places)

tgodzik · 2025-09-09T09:57:10Z

metals/src/main/scala/scala/meta/internal/metals/TwirlAdjustments.scala

+  private def resolveVersion(scalaVersion: String): String = {
+    val base = scalaVersion.split('-')(0)
+    base match {
+      case v if v.startsWith("2") => v.split('.').take(2).mkString(".")


Suggested change

case v if v.startsWith("2") => v.split('.').take(2).mkString(".")

case v if v.startsWith("2") =>ScalaVersions.scalaBinaryVersionFromFullVersion(v)

also, do you know why for Scala 3 we have a full version and not just "3" ?

To be honest, I had this function for resolving file paths when we used the compiled .template.scala files from target/scala-XX/twirl/main/example.template.scala. I noticed that Scala 2 versions usually took the form target/scala-2.13/ or target/scala-2.12/, while in Scala 3, they took the form target/scala-3.7.2/, etc. This means that, Scala 2 versions include only the major and minor version numbers, whereas Scala 3 versions also include the patch version at the end (e.g., 3.7.2 instead of just 3.7).

After we started compiling it in memory, it served no real purpose.

why for Scala 3 we have a full version and not just "3"

TwirlCompiler.scala checks for scala versions like this, .startsWith("3.") instead of .startsWith("3"). So if we just do scalaVersion = Some("3"), it might get interpreted as compiling for a scala2 version instead 🫢.

One way we could do is remove the method resolveVersion entirely and just do Some(scalaVersion) instead of Some(resolveVersion(scalaVersion)). What do you think? 🤔

If it works I would opt for removing the method.

It worked!, I will push it along maybe some more commits so that the CI won't run for all of the commits.

PS - Is there a way on github to stop CI from running automatically? Because sometimes it's just a commit that changes comments etc, and I think the CI should be run automatically only when the full test suites are needed, or maybe when it's not a draft pr atleast 🤔.

You can add a tag to the commit like [skip ci], though that might only work in the PRs, not sure

tgodzik · 2025-09-09T10:00:46Z

metals/src/main/scala/scala/meta/internal/metals/TwirlAdjustments.scala

+   * @return An array of tuples representing (originalIndex, generatedIndex) pairs
+   */
+  private def getMatrix(compiledTwirl: String): Array[(Int, Int)] = {
+    val pattern = """(\d+)->(\d+)""".r


You can extract that patter outside so that it's not recompiled every time.

tgodzik · 2025-09-09T10:05:17Z

tests/slow/src/test/scala/tests/sbt/SbtTwirlSuite.scala

+      _ <- assertCompletionEdit(
+        "File@@",
+        """
+          |@import java.io.File


There seems to be small issue that if a second symbol such as Paths is imported then no newline is inserted.

was able to reproduce it, will fix it and add it to the twirl-import test.

Hmm, the fix is kinda weird for me 😅 , and I couldn't find something satisfactory yet, for now instead of prepending @, I basically prepend \n@ , this provides autoimports that actually work, but there is an extra new line at the start 😢 .

Also, I could've swore the imports were working correctly on sbt-twirl instead of an the webjar play project. Have to investigate more 🫨 .

this might be due to the reverse mapping. We might be losing some newlines because of that. MAybe it's fine to add \n@ for now 🤔

tgodzik · 2025-09-09T10:05:51Z

tests/slow/src/test/scala/tests/sbt/SbtTwirlSuite.scala

+      res <- definitionsAt(
+        "src/main/twirl/example.scala.html",
+        """|@(name: String)
+           |<h1>Hello @name.toI@@nt</h1>


We should also add a check for "name", can just be the next step like:

res2...

tgodzik · 2025-10-03T11:20:03Z

@ajafri2001 will you have time to finish this?

ajafri2001 · 2025-10-03T20:44:14Z

@ajafri2001 will you have time to finish this?

oh yes I forgot, I'll wrap it up by tomorrow.

ajafri2001 · 2025-10-15T19:53:01Z

Am in last stretch of exam season, HAVE NOT ABANDONED!

ajafri2001 and others added 20 commits July 1, 2025 18:58

solid progress

2bbfab6

Improved formatting

3923c42

Added TwirlSuite

59ed984

Wip commit

ac617ee

completions don't work

c6fe993

removed vars

b787d54

wip add tests and docs

ba91d3c

added play imports

6af579c

format

5850a63

format

45c3364

WIP - Added play's DI

28de74f

wip - fixed twirl imports

8984c6b

remove publishDiagnostics for twirl files

306300d

added tests

e61bed8

Merge branch 'main' into metals-play

a1b9ac8

Merge pull request #2 from ajafri2001/metals-play

a2a181f

Add twirl support

remove duplicate test from completionlspsuite.scala

9fdeab3

fix tests

3c1bce9

add import and rename tests

921ebb1

fix twirl-hover-method test

7329e96

ajafri2001 self-assigned this Aug 30, 2025

tgodzik requested changes Sep 9, 2025

View reviewed changes

Accomodate review changes

0ef0e15

Merge branch 'scalameta:main' into main

113c98d

		if (locations.asScala.forall(loc => originalUri.equals(loc.getUri())))
		adjust.adjustLocations(locations)

	case v if v.startsWith("2") => v.split('.').take(2).mkString(".")
	case v if v.startsWith("2") =>ScalaVersions.scalaBinaryVersionFromFullVersion(v)

Twirl support in metals #7751

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Twirl support in metals #7751

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tgodzik commented Oct 3, 2025

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ajafri2001 commented Oct 3, 2025

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ajafri2001 commented Oct 15, 2025

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