Merge pull request #44 from mkantor/panic-keyword

Add `@panic` keyword expression

Author: mkantor

README.md

@@ -153,7 +153,7 @@ keyword expressions.
 Under the hood, keyword expressions are modeled as objects. For example, `:foo`
 desugars to `{@lookup key: foo}`. All such expressions have a key `0` referring
 to a value that is an `@`-prefixed atom (the keyword). Keywords include
-`@function`, `@lookup`, `@apply`, `@check`, `@index`, and `@runtime`.
+`@function`, `@lookup`, `@apply`, `@check`, `@index`, `@panic`, and `@runtime`.
 
 Currently only `@function`, `@lookup`, `@index`, and `@apply` have syntax
 sugars.

src/end-to-end.test.ts

@@ -27,6 +27,22 @@ testCases(endToEnd, code => code)('end-to-end tests', [
   ['{a,1:overwritten,c}', either.makeRight({ 0: 'a', 1: 'c' })],
   ['{overwritten,0:a,c}', either.makeRight({ 0: 'a', 1: 'c' })],
   ['{@check type:true value:true}', either.makeRight('true')],
+  [
+    '{@panic}',
+    result => {
+      assert(either.isLeft(result))
+      assert('kind' in result.value)
+      assert.deepEqual(result.value.kind, 'panic')
+    },
+  ],
+  [
+    '{@runtime _ => {@panic}}',
+    result => {
+      assert(either.isLeft(result))
+      assert('kind' in result.value)
+      assert.deepEqual(result.value.kind, 'panic')
+    },
+  ],
   ['{a:A b:{@lookup a}}', either.makeRight({ a: 'A', b: 'A' })],
   ['{a:A b: :a}', either.makeRight({ a: 'A', b: 'A' })],
   ['{a:A {@lookup a}}', either.makeRight({ a: 'A', 0: 'A' })],

src/language/compiling/semantics/keyword-handlers/panic-handler.test.ts

@@ -0,0 +1,27 @@
+import either from '@matt.kantor/either'
+import assert from 'node:assert'
+import { elaborationSuite } from '../test-utilities.test.js'
+
+elaborationSuite('@panic', [
+  [
+    { 0: '@panic' },
+    output => {
+      assert(either.isLeft(output))
+      assert.deepEqual(output.value.kind, 'panic')
+    },
+  ],
+  [
+    { 0: '@panic', 1: 'blah' },
+    output => {
+      assert(either.isLeft(output))
+      assert.deepEqual(output.value.kind, 'panic')
+    },
+  ],
+  [
+    { 0: '@panic', message: { a: { b: 'c' } } },
+    output => {
+      assert(either.isLeft(output))
+      assert.deepEqual(output.value.kind, 'panic')
+    },
+  ],
+])

src/language/compiling/semantics/keyword-handlers/panic-handler.ts

@@ -0,0 +1,19 @@
+import either, { type Either } from '@matt.kantor/either'
+import type { ElaborationError } from '../../../errors.js'
+import {
+  asSemanticGraph,
+  stringifySemanticGraphForEndUser,
+  type Expression,
+  type ExpressionContext,
+  type KeywordHandler,
+  type SemanticGraph,
+} from '../../../semantics.js'
+
+export const panicKeywordHandler: KeywordHandler = (
+  expression: Expression,
+  _context: ExpressionContext,
+): Either<ElaborationError, SemanticGraph> =>
+  either.makeLeft({
+    kind: 'panic',
+    message: stringifySemanticGraphForEndUser(asSemanticGraph(expression)),
+  })

src/language/compiling/semantics/keywords.ts

@@ -4,6 +4,7 @@ import { checkKeywordHandler } from './keyword-handlers/check-handler.js'
 import { functionKeywordHandler } from './keyword-handlers/function-handler.js'
 import { indexKeywordHandler } from './keyword-handlers/index-handler.js'
 import { lookupKeywordHandler } from './keyword-handlers/lookup-handler.js'
+import { panicKeywordHandler } from './keyword-handlers/panic-handler.js'
 import { runtimeKeywordHandler } from './keyword-handlers/runtime-handler.js'
 import { todoKeywordHandler } from './keyword-handlers/todo-handler.js'
 
@@ -33,6 +34,11 @@ export const keywordHandlers: KeywordHandlers = {
    */
   '@lookup': lookupKeywordHandler,
 
+  /**
+   * Immediately terminates the process when evaluated.
+   */
+  '@panic': panicKeywordHandler,
+
   /**
    * Defers evaluation until runtime.
    */

src/language/semantics/keyword.ts

@@ -4,6 +4,7 @@ export const isKeyword = (input: string) =>
   input === '@function' ||
   input === '@index' ||
   input === '@lookup' ||
+  input === '@panic' ||
   input === '@runtime' ||
   input === '@todo'