Give useful exceptions when a requested psi body is null

doks-gradle-plugin/src/main/kotlin/com/rickbusarow/doks/internal/psi/NamedSamples.kt

@@ -44,6 +44,7 @@ import org.jetbrains.kotlin.psi.psiUtil.getChildrenOfType
 import org.jetbrains.kotlin.psi.psiUtil.parents
 import java.io.File
 import kotlin.LazyThreadSafetyMode.NONE
+import kotlin.contracts.contract
 import kotlin.io.path.Path
 
 @Serializable
@@ -118,29 +119,35 @@ internal class NamedSamples(
       val content =
         when (val namedDeclaration = cache[request.fqName]) {
           is KtClassOrObject -> if (request.bodyOnly) {
-            namedDeclaration.body!!.textInScope()
+            namedDeclaration.body
+              .requireBodyNotNull(namedDeclaration, request.fqName) {
+                "A type declaration must have a body"
+              }
+              .textInScope()
           } else {
             namedDeclaration.text.trimIndentAfterFirstLine()
           }
 
           is KtProperty -> if (request.bodyOnly) {
             namedDeclaration.initializer
-              .requireNotNull {
-                "${namedDeclaration.containingKtFile} > " +
-                  "A property must have an initializer when using 'bodyOnly = true'."
+              .requireBodyNotNull(namedDeclaration, request.fqName) {
+                "A property must have an initializer"
               }
               .let { (it as? KtStringTemplateExpression) ?: it.getChildOfType() }
-              .requireNotNull {
-                "${namedDeclaration.containingKtFile} > " +
-                  "A property initializer must be a string template."
+              .requireBodyNotNull(namedDeclaration, request.fqName) {
+                "A property initializer must be a string template"
               }
               .textInScope()
           } else {
             namedDeclaration.text
           }
 
           is KtNamedFunction -> if (request.bodyOnly) {
-            namedDeclaration.bodyBlockExpression!!.textInScope()
+            namedDeclaration.bodyBlockExpression
+              .requireBodyNotNull(namedDeclaration, request.fqName) {
+                "A function must use body syntax"
+              }
+              .textInScope()
           } else {
             namedDeclaration.text.trimIndentAfterFirstLine()
           }
@@ -156,6 +163,26 @@ internal class NamedSamples(
     }
   }
 
+  inline fun <T : Any> T?.requireBodyNotNull(
+    psi: KtElement,
+    fqName: String,
+    message: () -> String
+  ): T {
+    contract {
+      returns() implies (this@requireBodyNotNull != null)
+    }
+    return requireNotNull(this) {
+      """
+      |${psi.containingKtFile.absolutePath()} > ${message()} when using 'bodyOnly = true'.
+      |requested name: $fqName
+      |matched code:
+      |---
+      |${psi.text.trimIndentAfterFirstLine()}
+      |---
+      """.trimMargin()
+    }
+  }
+
   private fun createDeclarationCache(
     ktFiles: Sequence<KtFile>,
     requests: List<SampleRequest>

doks-gradle-plugin/src/main/kotlin/com/rickbusarow/doks/internal/stdlib/string.kt

@@ -133,7 +133,13 @@ internal fun String.remove(vararg regex: Regex): String = regex.fold(this) { acc
 
 internal fun String.trimIndentAfterFirstLine(): String {
   val split = lines()
+
+  // If there's only one line, there's nothing to trim,
+  // and the remaining logic would just append an extra newline.
+  if (split.size == 1) return this
+
   val first = split.first()
-  val remaining = split.drop(1).joinToString("\n").trimIndent()
+  val remaining = split.drop(1).joinToString("\n")
+    .trimIndent()
   return "$first\n$remaining"
 }

doks-gradle-plugin/src/test/kotlin/com/rickbusarow/doks/internal/psi/NamedSamplesTest.kt

@@ -16,6 +16,7 @@
 package com.rickbusarow.doks.internal.psi
 
 import io.kotest.assertions.throwables.shouldNotThrowAny
+import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.matchers.shouldBe
 import org.intellij.lang.annotations.Language
 import org.junit.jupiter.api.Test
@@ -239,6 +240,95 @@ class NamedSamplesTest {
     """.trimIndent()
   }
 
+  @Test
+  fun `an class without a body and bodyOnly = true`() {
+
+    // test for: https://github.com/rickbusarow/Doks/issues/223
+
+    val exception = shouldThrow<IllegalArgumentException> {
+      parse(
+        fqName = "com.test.MyClass",
+        bodyOnly = true,
+        """
+      package com.test
+
+      class MyClass
+      """
+      )
+    }
+
+    exception.message shouldBe """
+      src/Source_0.kt > A type declaration must have a body when using 'bodyOnly = true'.
+      requested name: com.test.MyClass
+      matched code:
+      ---
+      class MyClass
+      ---
+    """.trimIndent()
+  }
+
+  @Test
+  fun `an expression syntax function that invokes a lambda and bodyOnly = true`() {
+
+    // test for: https://github.com/rickbusarow/Doks/issues/223
+
+    val exception = shouldThrow<IllegalArgumentException> {
+      parse(
+        fqName = "com.test.MyClass.myFunction",
+        bodyOnly = true,
+        """
+      package com.test
+
+      class MyClass {
+        fun myFunction() = runBlocking {
+          println("boo!")
+        }
+      }
+      """
+      )
+    }
+
+    exception.message shouldBe """
+      src/Source_0.kt > A function must use body syntax when using 'bodyOnly = true'.
+      requested name: com.test.MyClass.myFunction
+      matched code:
+      ---
+      fun myFunction() = runBlocking {
+        println("boo!")
+      }
+      ---
+    """.trimIndent()
+  }
+
+  @Test
+  fun `an expression syntax function that does not invoke lambda and bodyOnly = true`() {
+
+    // test for: https://github.com/rickbusarow/Doks/issues/223
+
+    val exception = shouldThrow<IllegalArgumentException> {
+      parse(
+        fqName = "com.test.MyClass.myFunction",
+        bodyOnly = true,
+        """
+      package com.test
+
+      class MyClass {
+        fun myFunction() = Unit
+      }
+      """
+      )
+    }
+
+    exception.message shouldBe """
+      src/Source_0.kt > A function must use body syntax when using 'bodyOnly = true'.
+      requested name: com.test.MyClass.myFunction
+      matched code:
+      ---
+      fun myFunction() = Unit
+      ---
+    """.trimIndent()
+  }
+
   @Test
   fun `a variable inside a nested function can be resolved`() {
 
@@ -370,7 +460,6 @@ class NamedSamplesTest {
       """
     ) shouldBe """
       |object Foo
-      |
     """.trimMargin()
   }
 
@@ -379,7 +468,7 @@ class NamedSamplesTest {
       DoksPsiFileFactory()
         .createKotlin(
           name = "Source_$index.kt",
-          path = "Source_$index.kt",
+          path = "src/Source_$index.kt",
           content = code.trimIndent()
         )
     }