Merge task-007: add unnecessary else linter (resolved conflict)

Author: bm1549

buildSrc/build.gradle.kts

@@ -64,6 +64,11 @@ gradlePlugin {
       id = "dd-trace-java.empty-instrumentation-linter"
       implementationClass = "datadog.gradle.plugin.lint.EmptyInstrumentationLinter"
     }
+
+    create("unnecessary-else-linter") {
+      id = "dd-trace-java.unnecessary-else-linter"
+      implementationClass = "datadog.gradle.plugin.lint.UnnecessaryElseLinter"
+    }
   }
 }
 

buildSrc/src/main/kotlin/datadog/gradle/plugin/lint/UnnecessaryElseLinter.kt

@@ -0,0 +1,111 @@
+package datadog.gradle.plugin.lint
+
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+
+class UnnecessaryElseLinter : Plugin<Project> {
+  override fun apply(target: Project) {
+    target.tasks.register("checkUnnecessaryElse") {
+      group = "verification"
+      description = "Scan changed Java files for unnecessary else blocks after return/throw/continue/break"
+
+      doLast {
+        val baseSha = "9b933669729ea8a7af00f5cf3c36b6720ec433bd"
+        val changedFiles = getChangedJavaFiles(target, baseSha)
+        val repoRoot = target.rootProject.projectDir.toPath()
+        val warnings = mutableListOf<String>()
+
+        changedFiles.forEach { file ->
+          if (file.exists()) {
+            val relPath = repoRoot.relativize(file.toPath()).toString()
+            checkFile(file, relPath, warnings)
+          }
+        }
+
+        if (warnings.isNotEmpty()) {
+          warnings.forEach { target.logger.warn(it) }
+          target.logger.warn("Found ${warnings.size} unnecessary else block(s) — advisory only.")
+        } else {
+          target.logger.info("No unnecessary else blocks found in changed files.")
+        }
+      }
+    }
+  }
+}
+
+private fun getChangedJavaFiles(project: Project, baseSha: String): List<java.io.File> {
+  return try {
+    val process = ProcessBuilder("git", "diff", "--name-only", baseSha, "HEAD")
+      .directory(project.rootProject.projectDir)
+      .redirectErrorStream(true)
+      .start()
+    val output = process.inputStream.bufferedReader().readText()
+    process.waitFor()
+    output.trim().lines()
+      .filter { it.isNotBlank() && it.endsWith(".java") }
+      .map { project.rootProject.projectDir.resolve(it) }
+      .filter { it.exists() }
+  } catch (e: Exception) {
+    project.logger.warn("checkUnnecessaryElse: could not get changed files — ${e.message}")
+    emptyList()
+  }
+}
+
+private fun checkFile(file: java.io.File, relPath: String, warnings: MutableList<String>) {
+  val lines = file.readLines()
+  val elsePattern = Regex("""^\s*\}\s*else\s*(\{.*)?$""")
+
+  for (i in lines.indices) {
+    if (!elsePattern.containsMatchIn(lines[i])) continue
+    if (isUnnecessaryElse(lines, i)) {
+      warnings.add("STYLE: $relPath:${i + 1} — unnecessary else after return/throw/continue/break")
+    }
+  }
+}
+
+private fun isUnnecessaryElse(lines: List<String>, elseLineIdx: Int): Boolean {
+  // Walk backwards from "} else {" to find the last meaningful statement
+  var j = elseLineIdx - 1
+  while (j >= 0) {
+    val trimmed = lines[j].trim()
+    if (trimmed.isEmpty() || isCommentLine(trimmed)) {
+      j--
+      continue
+    }
+    // The last non-empty line before "} else {" must end with ";" to be a statement boundary
+    if (!trimmed.endsWith(";")) return false
+
+    // Check if this single line is itself an exit statement
+    if (isExitStatement(trimmed)) return true
+
+    // For multi-line statements (e.g. multi-line return/throw), walk further back
+    // looking for the start of the statement (a line not ending with a continuation)
+    var k = j - 1
+    while (k >= 0) {
+      val prev = lines[k].trim()
+      if (prev.isEmpty() || isCommentLine(prev)) {
+        k--
+        continue
+      }
+      // Another complete statement or block boundary — stop
+      if (prev.endsWith(";") || prev.endsWith("{") || prev.endsWith("}")) return false
+      // This line is a continuation of the same statement
+      if (startsWithExitKeyword(prev)) return true
+      k--
+    }
+    return false
+  }
+  return false
+}
+
+private fun isCommentLine(trimmed: String) =
+  trimmed.startsWith("//") || trimmed.startsWith("*") || trimmed.startsWith("/*")
+
+private fun isExitStatement(trimmed: String) =
+  startsWithExitKeyword(trimmed)
+
+private fun startsWithExitKeyword(trimmed: String) =
+  trimmed.startsWith("return ") || trimmed == "return;" ||
+    trimmed.startsWith("throw ") ||
+    trimmed == "continue;" || trimmed.startsWith("continue ") ||
+    trimmed == "break;" || trimmed.startsWith("break ")