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Implement hover, completions and signature help.
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This is a large commit that adds new infrastructure to use the Scala
presentation compiler for interactive features like completions and
"show type".

This commit implements several features together because we could have
used a simpler architecture if we for example only implemented hover
first. That architecture would then need to be redesigned as we
implemented more features. Instead, by implmenting several features
together we reach the final design faster.

Features
--------

The presentation compiler provides decent APIs to implement hover and
completions. We make a few customizations:

- signature help is implemented from scratch using a custom tree traverser
  to track the active argument tree, including named arguments.
- scope completions perform a workspace/symbol search for symbols that
  are not in scope.
- we use our own fuzzy string matcher so for example `uService<TAB>`
  matches `userDatabaseService`.
- Java and Scala docstrings are extracted from library dependency
  sources.
- we have a custom signature printer that implements several niceties:
  - fully qualified types are shortened so they are easier to read, take
  up less space.
  - Java parameter names are extracted from library source code to avoid
  method signatures with parameters named `x$1`. A lot of Java code
  (including the JDK) is not compiled with -parameter so the only way to
  recover the parameter names is from source code.
  - Scala parameter default values are extracted from source when
  possible, for example `Iterator.sliding(size: Int, step: Int = 1)`
  instead of `Iterator.sliding(size: Int, step: Int = {})`.

Performance
-----------

It costs around 150-250ms to start a new presentation compiler, which
happens every time a build target has finished compilation.

Benchmarks show that a warmed up presentation compiler responds
comfortably within 100ms even for large source files with 7k lines of
code. I suspect the performance is slower for macro-heavy code, but
I was nevertheless impressed by the performance in the cases I tried.

Build changes
-------------

The following projects have been added to the sbt build:
- `pc-interfaces` module that is a pure Java API enabling Metals
  to communicate with the 2.11/2.12 compiler via reflection.
- `pc` module that is cross-built against exact Scala compiler
  versions and implements the `pc-interfaces` Java APIs, support both
  Scala 2.11 and 2.12.
- internal `cross` module that is used for testing 2.11/2.12
  cross-built modules like `pc`.
- internal `mtest` module that is used for sharing testing
  infrastructure between 2.11 and 2.12.

The implementation for workspace/symbol has moved from the `metals`
project into the `pc` project to facilitate testing on 2.11.
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@olafurpg
olafurpg committed Mar 7, 2019
1 parent c0a1330 commit 80341b7
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2 changes: 1 addition & 1 deletion .jvmopts
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@@ -1,6 +1,6 @@
-Xss4m
-Xms1G
-Xmx4G
-Xmx5G
-XX:ReservedCodeCacheSize=1024m
-XX:+TieredCompilation
-XX:+CMSClassUnloadingEnabled
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1 change: 1 addition & 0 deletions .scalafmt.conf
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Expand Up @@ -13,6 +13,7 @@ To fix this problem:

project.excludeFilters = [
"test-workspace"
"metals-bench/src/main/resources"
"tests/unit/src/test/resources"
"sbt-metals/src/sbt-test"
]
218 changes: 218 additions & 0 deletions NOTICE.md
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Expand Up @@ -242,3 +242,221 @@ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
```

# License notice for Akka
Metals contains parts which are derived from
[the akka project](https://github.com/akka/akka). We
include the text of the original license below:

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63 changes: 60 additions & 3 deletions build.sbt
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@@ -1,8 +1,9 @@
def localSnapshotVersion = "0.5.0-SNAPSHOT"
def isCI = System.getProperty("CI") != null
inThisBuild(
List(
version ~= { dynVer =>
if (sys.env.contains("CI")) dynVer
if (isCI) dynVer
else localSnapshotVersion // only for local publishng
},
scalaVersion := V.scala212,
Expand Down Expand Up @@ -82,6 +83,7 @@ inThisBuild(
)

cancelable.in(Global) := true
crossScalaVersions := Nil

addCommandAlias("scalafixAll", "all compile:scalafix test:scalafix")
addCommandAlias("scalafixCheck", "; scalafix --check ; test:scalafix --check")
Expand Down Expand Up @@ -111,8 +113,36 @@ lazy val V = new {

skip.in(publish) := true

lazy val interfaces = project
.in(file("pc/interfaces"))
.settings(
moduleName := "pc-interfaces",
autoScalaLibrary := false,
libraryDependencies ++= List(
"org.eclipse.lsp4j" % "org.eclipse.lsp4j" % "0.5.0"
),
crossVersion := CrossVersion.disabled
)
lazy val pc = project
.in(file("pc/core"))
.settings(
moduleName := "pc",
crossVersion := CrossVersion.full,
crossScalaVersions := List(V.scala212, V.scala211),
libraryDependencies ++= {
if (isCI) Nil
else List("com.lihaoyi" %% "pprint" % "0.5.3")
},
libraryDependencies ++= List(
"org.scala-lang" % "scala-compiler" % scalaVersion.value,
"org.scalameta" % "semanticdb-scalac-core" % V.scalameta cross CrossVersion.full
)
)
.dependsOn(interfaces, mtags)

lazy val mtags = project
.settings(
moduleName := "mtags",
crossScalaVersions := List(V.scala212, V.scala211),
libraryDependencies ++= List(
"com.thoughtworks.qdox" % "qdox" % "2.0-M9", // for java mtags
Expand Down Expand Up @@ -191,7 +221,7 @@ lazy val metals = project
"scala212" -> V.scala212
)
)
.dependsOn(mtags)
.dependsOn(pc, mtags)
.enablePlugins(BuildInfoPlugin)

lazy val `sbt-metals` = project
Expand Down Expand Up @@ -229,6 +259,7 @@ lazy val input = project
"org.scalameta" %% "scalameta" % V.scalameta,
"io.circe" %% "circe-derivation-annotations" % "0.9.0-M5"
),
scalacOptions += "-P:semanticdb:synthetics:on",
addCompilerPlugin(
"org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full
)
Expand All @@ -240,6 +271,32 @@ lazy val testSettings: Seq[Def.Setting[_]] = List(
testFrameworks := List(new TestFramework("utest.runner.Framework"))
)

lazy val mtest = project
.in(file("tests/mtest"))
.settings(
skip.in(publish) := true,
crossScalaVersions := List(V.scala212, V.scala211),
libraryDependencies ++= List(
"com.geirsson" %% "coursier-small" % "1.3.3",
"org.scalameta" %% "testkit" % V.scalameta,
"com.lihaoyi" %% "utest" % "0.6.0"
),
buildInfoPackage := "tests",
buildInfoObject := "BuildInfoVersions",
buildInfoKeys := Seq[BuildInfoKey](
"scala211" -> V.scala211,
"scala212" -> V.scala212
)
)
.enablePlugins(BuildInfoPlugin)

lazy val cross = project
.in(file("tests/cross"))
.settings(
testSettings,
crossScalaVersions := V.supportedScalaVersions
)
.dependsOn(mtest, pc)
lazy val unit = project
.in(file("tests/unit"))
.settings(
Expand All @@ -262,7 +319,7 @@ lazy val unit = project
"testResourceDirectory" -> resourceDirectory.in(Test).value
)
)
.dependsOn(metals)
.dependsOn(mtest, metals, pc)
.enablePlugins(BuildInfoPlugin)
lazy val slow = project
.in(file("tests/slow"))
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15 changes: 15 additions & 0 deletions metals-bench/readme.md
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Expand Up @@ -45,6 +45,21 @@ Date: 2018 October 8th, commit 59bda2ac81a497fa168677499bd1a9df60fec5ab
[info] WorkspaceFuzzBench.upper abcdefghijklmnopqrstabcdefghijkl ss 30 202.464 ± 1.423 ms/op
```

## textDocument/completions

First results show that loading a global instance of every request is too expensive.

Commit: 65a2baea48637e44dc619dce46a164dc0aa055f9
```
[info] Benchmark (completion) Mode Cnt Score Error Units
[info] CachedSearchAndCompilerCompletionBench.complete scopeOpen ss 30 20.760 ± 1.387 ms/op
[info] CachedSearchAndCompilerCompletionBench.complete scopeDeep ss 30 61.732 ± 13.112 ms/op
[info] CachedSearchAndCompilerCompletionBench.complete memberDeep ss 30 62.284 ± 64.132 ms/op
[info] CachedSearchCompletionBench.complete scopeOpen ss 30 156.566 ± 178.618 ms/op
[info] CachedSearchCompletionBench.complete scopeDeep ss 30 233.977 ± 222.032 ms/op
[info] CachedSearchCompletionBench.complete memberDeep ss 30 154.681 ± 198.653 ms/op
```

## Flamegraphs

Required steps before running.
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