Add err_teapot function

src/main/resources/messages/IdeaVimBundle.properties

@@ -67,6 +67,7 @@ E363=E363: pattern caused out-of-stack error
 E369=E369: invalid item in {0}%[]
 E384=E384: Search hit TOP without match for: {0}
 E385=E385: Search hit BOTTOM without match for: {0}
+E418=E418: I am a teapot
 E471=E471: Argument required
 E474=E474: Invalid argument: {0}
 E475=E475: Invalid argument: {0}
@@ -77,6 +78,7 @@ E488=E488: Trailing characters: {0}
 # Vim's message includes alternate files and the :p:h file name modifier, which we don't support
 # E499: Empty file name for '%' or '#', only works with ":p:h"
 E499=E499: Empty file name for '%'
+E503=E503: Coffee is currently not available
 E518=E518: Unknown option: {0}
 E521=E521: Number required after =: {0}
 E545=E545: Missing colon: {0}

src/test/java/org/jetbrains/plugins/ideavim/ex/implementation/functions/variousFunctions/ErrTeapotFunctionTest.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2003-2025 The IdeaVim authors
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE.txt file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+package org.jetbrains.plugins.ideavim.ex.implementation.functions.variousFunctions
+
+import org.jetbrains.plugins.ideavim.VimTestCase
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.TestInfo
+
+class ErrTeapotFunctionTest : VimTestCase() {
+  @BeforeEach
+  override fun setUp(testInfo: TestInfo) {
+    super.setUp(testInfo)
+    configureByText("\n")
+  }
+
+  @Test
+  fun `test err_teapot`() {
+    enterCommand("echo err_teapot()")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E418: I am a teapot")
+  }
+
+  @Test
+  fun `test err_teapot with boolean false argument`() {
+    enterCommand("echo err_teapot(0)")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E418: I am a teapot")
+  }
+
+  @Test
+  fun `test err_teapot with boolean true argument`() {
+    enterCommand("echo err_teapot(1)")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E503: Coffee is currently not available")
+  }
+
+  @Test
+  fun `test err_teapot with false string argument`() {
+    enterCommand("echo err_teapot(\"0\")")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E418: I am a teapot")
+  }
+
+  @Test
+  fun `test err_teapot with true string argument`() {
+    enterCommand("echo err_teapot(\"1\")")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E503: Coffee is currently not available")
+  }
+
+  @Test
+  fun `test err_teapot with list argument`() {
+    enterCommand("echo err_teapot([0])")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E745: Using a List as a Number")
+  }
+
+  @Test
+  fun `test err_teapot with dictionary argument`() {
+    enterCommand("echo err_teapot({1: 0})")
+    assertPluginError(true)
+    assertPluginErrorMessageContains("E728: Using a Dictionary as a Number")
+  }
+}

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/vimscript/model/functions/handlers/variousFunctions/ErrTeapotFunctionHandler.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2003-2025 The IdeaVim authors
+ *
+ * Use of this source code is governed by an MIT-style
+ * license that can be found in the LICENSE.txt file or at
+ * https://opensource.org/licenses/MIT.
+ */
+
+package com.maddyhome.idea.vim.vimscript.model.functions.handlers.variousFunctions
+
+import com.intellij.vim.annotations.VimscriptFunction
+import com.maddyhome.idea.vim.api.ExecutionContext
+import com.maddyhome.idea.vim.api.VimEditor
+import com.maddyhome.idea.vim.ex.exExceptionMessage
+import com.maddyhome.idea.vim.vimscript.model.VimLContext
+import com.maddyhome.idea.vim.vimscript.model.datatypes.VimDataType
+import com.maddyhome.idea.vim.vimscript.model.expressions.Expression
+import com.maddyhome.idea.vim.vimscript.model.functions.FunctionHandler
+
+@VimscriptFunction(name = "err_teapot")
+class ErrTeapotFunctionHandler : FunctionHandler() {
+  override val minimumNumberOfArguments = 0
+  override val maximumNumberOfArguments: Int? = 1
+
+  override fun doFunction(
+    argumentValues: List<Expression>,
+    editor: VimEditor,
+    context: ExecutionContext,
+    vimContext: VimLContext,
+  ): VimDataType {
+    val arg1 = argumentValues.getOrNull(0)?.evaluate(editor, context, vimContext)?.asBoolean() ?: false
+    if (arg1) {
+      throw exExceptionMessage("E503")
+    }
+    else {
+      throw exExceptionMessage("E418")
+    }
+  }
+}

vim-engine/src/main/resources/ksp-generated/engine_vimscript_functions.json

@@ -10,6 +10,7 @@
     "cos": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.floatFunctions.CosFunctionHandler",
     "cosh": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.floatFunctions.CoshFunctionHandler",
     "empty": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.EmptyFunctionHandler",
+    "err_teapot": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.variousFunctions.ErrTeapotFunctionHandler",
     "escape": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.stringFunctions.EscapeFunctionHandler",
     "exists": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.variousFunctions.ExistsFunctionHandler",
     "exp": "com.maddyhome.idea.vim.vimscript.model.functions.handlers.floatFunctions.ExpFunctionHandler",