Add GradleSettingsVerifierCli (#71)

* Add GradleSettingsVerifierCli

* Exit with a failure

* Spotless

api/kotlin-cli-util.api

@@ -42,6 +42,11 @@ public final class slack/cli/gradle/GradleProjectFlattenerCli : com/github/ajalt
 	public fun run ()V
 }
 
+public final class slack/cli/gradle/GradleSettingsVerifierCli : com/github/ajalt/clikt/core/CliktCommand {
+	public fun <init> ()V
+	public fun run ()V
+}
+
 public final class slack/cli/lint/LintBaselineMergerCli : com/github/ajalt/clikt/core/CliktCommand {
 	public fun <init> ()V
 	public fun run ()V

src/main/kotlin/slack/cli/gradle/GradleSettingsVerifierCli.kt

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2023 Slack Technologies, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package slack.cli.gradle
+
+import com.github.ajalt.clikt.core.CliktCommand
+import com.github.ajalt.clikt.parameters.options.option
+import com.github.ajalt.clikt.parameters.options.required
+import com.github.ajalt.clikt.parameters.types.path
+import java.io.File
+import kotlin.io.path.ExperimentalPathApi
+import kotlin.io.path.exists
+import kotlin.io.path.isDirectory
+import kotlin.io.path.name
+import kotlin.io.path.readText
+import kotlin.io.path.relativeTo
+import kotlin.system.exitProcess
+import slack.cli.projectDirOption
+
+/** A CLI that verifies a given settings file has only valid projects. */
+public class GradleSettingsVerifierCli :
+  CliktCommand(help = "A CLI that verifies a given settings file has only valid projects.") {
+
+  private val projectDir by projectDirOption()
+
+  private val settingsFile by
+    option(
+        "--settings-file",
+        "-s",
+        help =
+          "The settings.gradle file to use. Note this file _must_ only have a single, top-level `include()` call " +
+            "with vararg project args."
+      )
+      .path(mustExist = true, canBeDir = false)
+      .required()
+
+  @ExperimentalPathApi
+  override fun run() {
+    val projectPaths =
+      settingsFile
+        .readText()
+        .trim()
+        .lines()
+        // Filter out commented lines
+        .filterNot { it.trimStart().startsWith("//") }
+        .joinToString("\n")
+        .removePrefix("include(")
+        .removeSuffix(")")
+        .split(",")
+
+    val errors = mutableListOf<String>()
+    @Suppress("LoopWithTooManyJumpStatements")
+    for (line in projectPaths) {
+      val path = line.trim().removeSurrounding("\"")
+      val realPath =
+        projectDir.resolve(path.removePrefix(":").removeSuffix(":").replace(":", File.separator))
+
+      fun reportError(message: String, column: Int) {
+        errors += buildString {
+          append(message)
+          appendLine(line)
+          appendLine("${" ".repeat(column)}^")
+        }
+      }
+
+      when {
+        path.endsWith(':') -> {
+          reportError("Project paths should not end with ':'", line.lastIndexOf(':') - 1)
+        }
+        !realPath.exists() -> {
+          reportError(
+            "Project dir '${realPath.relativeTo(projectDir)}' does not exist.",
+            line.indexOfFirst { !it.isWhitespace() }
+          )
+        }
+        !realPath.resolve("build.gradle.kts").exists() -> {
+          reportError(
+            "Project build file '${realPath.relativeTo(projectDir).resolve("build.gradle.kts")}' does not exist.",
+            line.indexOfFirst { !it.isWhitespace() }
+          )
+        }
+        !realPath.isDirectory() -> {
+          reportError(
+            "Expected '$realPath' to be a directory.",
+            line.indexOfFirst { !it.isWhitespace() }
+          )
+        }
+      }
+    }
+
+    if (errors.isNotEmpty()) {
+      echo("Errors found in '${settingsFile.name}'. Please fix or remove these.", err = true)
+      echo(errors.joinToString(""), err = true)
+      exitProcess(1)
+    }
+  }
+}