fix: Fix commit uuid sent in github actions (#232)

When using Github Actions and the on pull request trigger, the reporter was fetching an incorrect commit UUID

build.sbt

@@ -20,7 +20,8 @@ scalacOptions := Seq(
 libraryDependencies ++= Seq(
   "com.codacy" %% "coverage-parser" % "2.5.6",
   "com.github.alexarchambault" %% "case-app" % "1.2.0",
-  "org.wvlet.airframe" %% "airframe-log" % "20.5.1"
+  "org.wvlet.airframe" %% "airframe-log" % "20.5.1",
+  "com.lihaoyi" %% "ujson" % "1.1.0"
 )
 
 // Test dependencies

src/main/scala/com/codacy/rules/commituuid/providers/GitHubActionProvider.scala

@@ -1,15 +1,56 @@
 package com.codacy.rules.commituuid.providers
 
-import com.codacy.rules.commituuid.CommitUUIDProvider
+import java.io.File
+import java.nio.file.Files
+
 import com.codacy.model.configuration.CommitUUID
+import com.codacy.rules.commituuid.CommitUUIDProvider
+import wvlet.log.LazyLogger
 
-class GitHubActionProvider extends CommitUUIDProvider {
+import scala.util.Try
+
+class GitHubActionProvider extends CommitUUIDProvider with LazyLogger {
   val name: String = "GitHub Actions"
 
-  override def validate(a: Map[String, String]): Boolean = {
-    a.get("CI").contains("true") && a.get("GITHUB_ACTIONS").contains("true")
+  override def validate(envVars: Map[String, String]): Boolean = {
+    envVars.get("CI").contains("true") && envVars.get("GITHUB_ACTIONS").contains("true")
+  }
+
+  override def getUUID(envVars: Map[String, String]): Either[String, CommitUUID] = {
+    // if the event is a pull request the GITHUB_SHA will have a different commit UUID (the id of a merge commit)
+    // https://help.github.com/en/actions/reference/events-that-trigger-workflows
+    // for this reason, we need to fetch it from the event details that GitHub provides
+    // equivalent to doing ${{github.event.pull_request.head.sha}} in a GitHub action workflow
+    if (envVars.get("GITHUB_EVENT_NAME").contains("pull_request")) {
+      getPullRequestCommit(envVars)
+    } else {
+      withErrorMessage(envVars.get("GITHUB_SHA"))
+    }
   }
 
-  override def getUUID(a: Map[String, String]): Either[String, CommitUUID] =
-    withErrorMessage(a.get("GITHUB_SHA"))
+  private def getPullRequestCommit(envVars: Map[String, String]): Either[String, CommitUUID] = {
+    for {
+      eventPath <- envVars.get("GITHUB_EVENT_PATH").toRight("Could not find event description file path")
+      eventContent <- readFile(eventPath)
+      sha <- extractHeadSHA(eventContent)
+    } yield CommitUUID(sha)
+  }
+
+  private def readFile(path: String): Either[String, String] = {
+    val contentTry = Try {
+      val fileBytes = Files.readAllBytes(new File(path).toPath)
+      new String(fileBytes)
+    }
+
+    contentTry.toEither.left.map { ex =>
+      logger.error("Failed to read event file", ex)
+      s"Failed to read event file with error: ${ex.getMessage}"
+    }
+  }
+
+  private def extractHeadSHA(event: String) = {
+    val eventJson = ujson.read(event)
+    Try(eventJson("pull_request")("head")("sha").str).toEither.left
+      .map(t => s"Unable to fetch SHA from event file. Failed with error: ${t.getMessage}")
+  }
 }