lint against unknown step attributes

package.json

@@ -47,7 +47,7 @@
 		"command-line-args": "^5.2.0",
 		"command-line-usage": "^6.1.1",
 		"dedent-js": "^1.0.1",
-		"ecmarkdown": "^7.1.0",
+		"ecmarkdown": "^7.2.0",
 		"eslint-formatter-codeframe": "^7.32.1",
 		"fast-glob": "^3.2.7",
 		"grammarkdown": "^3.2.0",

src/lint/collect-algorithm-diagnostics.ts

@@ -10,12 +10,14 @@ import lintAlgorithmLineStyle from './rules/algorithm-line-style';
 import lintAlgorithmStepNumbering from './rules/algorithm-step-numbering';
 import lintAlgorithmStepLabels from './rules/algorithm-step-labels';
 import lintForEachElement from './rules/for-each-element';
+import lintStepAttributes from './rules/step-attributes';
 
 const algorithmRules = [
   lintAlgorithmLineStyle,
   lintAlgorithmStepNumbering,
   lintAlgorithmStepLabels,
   lintForEachElement,
+  lintStepAttributes,
 ];
 
 function composeObservers(...observers: Observer[]): Observer {

src/lint/rules/algorithm-step-labels.ts

@@ -15,14 +15,14 @@ export default function (report: Reporter, node: Element, algorithmSource: strin
       const idAttr = node.attrs.find(({ key }) => key === 'id');
       if (idAttr != null && !/^step-/.test(idAttr.value)) {
         const itemSource = algorithmSource.slice(
-          node.location.start.offset,
-          node.location.end.offset
+          idAttr.location.start.offset,
+          idAttr.location.end.offset
         );
-        const offset = itemSource.match(/^\s*\d+\. \[ *id *= *"/)![0].length;
+        const offset = itemSource.match(/^id *= *"/)![0].length;
         report({
           ruleId,
-          line: node.location.start.line,
-          column: node.location.start.column + offset,
+          line: idAttr.location.start.line,
+          column: idAttr.location.start.column + offset,
           message: `step labels should start with "step-"`,
         });
       }

src/lint/rules/step-attributes.ts

@@ -0,0 +1,29 @@
+import type { Node as EcmarkdownNode, Observer } from 'ecmarkdown';
+import type { Reporter } from '../algorithm-error-reporter-type';
+
+const ruleId = 'unknown-step-attribute';
+
+const KNOWN_ATTRIBUTES = ['id', 'fence-effects'];
+
+/*
+Checks for unknown attributes on steps.
+*/
+export default function (report: Reporter): Observer {
+  return {
+    enter(node: EcmarkdownNode) {
+      if (node.name !== 'ordered-list-item') {
+        return;
+      }
+      for (const attr of node.attrs) {
+        if (!KNOWN_ATTRIBUTES.includes(attr.key)) {
+          report({
+            ruleId,
+            message: `unknown step attribute ${JSON.stringify(attr.key)}`,
+            line: attr.location.start.line,
+            column: attr.location.start.column,
+          });
+        }
+      }
+    },
+  };
+}

test/lint-algorithms.js

@@ -391,6 +391,22 @@ describe('linting algorithms', () => {
     });
   });
 
+  describe('step attributes', () => {
+    const ruleId = 'unknown-step-attribute';
+    it('rejects unknown attributes', async () => {
+      await assertLint(
+        positioned`<emu-alg>
+          1. [id="step-id",${M}unknown="foo"] Step.
+        </emu-alg>`,
+        {
+          ruleId,
+          nodeType,
+          message: 'unknown step attribute "unknown"',
+        }
+      );
+    });
+  });
+
   describe('for each element', () => {
     const ruleId = 'for-each-element';
     it('rejects loops without types', async () => {