UndefinedObject: don't report continue in a for loop offset

.changeset/undefined-object-offset-continue.md

@@ -0,0 +1,5 @@
+---
+'@shopify/theme-check-common': patch
+---
+
+Stop `UndefinedObject` from reporting `continue` in `{% for ... offset: continue %}`. It is a Liquid keyword there, not a variable.

packages/theme-check-common/src/checks/undefined-object/index.spec.ts

@@ -121,6 +121,41 @@ describe('Module: UndefinedObject', () => {
     expect(offenses).toHaveLength(0);
   });
 
+  it('should not report an offense for the continue keyword in a for loop offset', async () => {
+    const sourceCode = `
+      {% for product in collections.all.products limit: 3 %}{{ product.title }}{% endfor %}
+      {% for product in collections.all.products limit: 3 offset: continue %}{{ product.title }}{% endfor %}
+      {%- for product in collections.all.products
+        limit: 3
+        offset: continue
+      -%}
+        {{ product.title }}
+      {%- endfor -%}
+    `;
+
+    const offenses = await runLiquidCheck(UndefinedObject, sourceCode);
+
+    expect(offenses).toHaveLength(0);
+  });
+
+  it('should report an offense when continue is used as a variable outside of a for loop offset', async () => {
+    const sourceCode = `
+      {{ continue }}
+      {% for product in collections.all.products limit: continue %}{% endfor %}
+      {% for product in collections.all.products offset: continue.size %}{% endfor %}
+      {% tablerow product in collections.all.products offset: continue %}{% endtablerow %}
+    `;
+
+    const offenses = await runLiquidCheck(UndefinedObject, sourceCode);
+
+    expect(offenses.map((e) => e.message)).toEqual([
+      "Unknown object 'continue' used.",
+      "Unknown object 'continue' used.",
+      "Unknown object 'continue' used.",
+      "Unknown object 'continue' used.",
+    ]);
+  });
+
   it('should report an offense when object is defined in a for loop but used outside of the scope', async () => {
     const sourceCode = `
       {% for c in collections %}

packages/theme-check-common/src/checks/undefined-object/index.ts

@@ -151,6 +151,7 @@ export const UndefinedObject: LiquidCheckDefinition = {
 
         const parent = last(ancestors);
         if (isLiquidTag(parent) && isLiquidTagCapture(parent)) return;
+        if (isForOffsetContinue(node, ancestors)) return;
 
         variables.push(node);
       },
@@ -298,6 +299,26 @@ function isDefinedInScope(variablePosition: Position, scope: Scope) {
   return isVariableAfterScopeStart && isVariableBeforeScopeEnd;
 }
 
+/**
+ * {% for x in y offset: continue %}
+ *
+ * `continue` is a keyword here, not a variable: it resumes the loop where the
+ * last loop over the same collection stopped. Only `for` supports it, not
+ * `tablerow`.
+ */
+function isForOffsetContinue(node: LiquidVariableLookup, ancestors: LiquidHtmlNode[]): boolean {
+  if (node.name !== 'continue' || node.lookups.length > 0) return false;
+
+  const [tag, markup, argument] = ancestors.slice(-3);
+  return (
+    argument?.type === NodeTypes.NamedArgument &&
+    argument.name === 'offset' &&
+    markup?.type === NodeTypes.ForMarkup &&
+    isLiquidTag(tag) &&
+    tag.name === NamedTags.for
+  );
+}
+
 function isLiquidTag(node?: LiquidHtmlNode): node is LiquidTag {
   return node?.type === NodeTypes.LiquidTag;
 }