--- name: shopify-functions description: 'Build Shopify Functions for custom discount, payment, and delivery logic in a WASM sandbox. Use when creating custom discount rules, payment customizations, delivery options, or cart transformations that run server-side at checkout. Trigger with phrases like "shopify functions", "shopify discounts", "shopify wasm", "custom discount function", "shopify checkout customization". ' allowed-tools: Read, Write, Edit, Bash(npm:*), Grep version: 2.7.0 license: MIT author: Jeremy Longshore tags: - saas - ecommerce - shopify compatibility: Designed for Claude Code --- # Shopify Functions ## Overview Shopify Functions execute custom business logic in a WebAssembly sandbox at checkout: discounts, payment filtering, delivery customization, and cart transforms. They run server-side with strict constraints (11ms execution, 1MB memory, no network access) and replace Shopify Scripts. ## Prerequisites - Shopify CLI 3.x+ installed (`npm install -g @shopify/cli`) - Shopify Partners account with a development store - App configured for the target function API type ## Instructions ### Step 1: Configure the Function Extension ```toml # extensions/product-discount/shopify.extension.toml api_version = "2025-01" type = "product_discounts" [[targeting]] target = "purchase.product-discount.run" input_query = "extensions/product-discount/input.graphql" export = "run" ``` ### Step 2: Define the Input Query The input query declares what data your function receives at runtime: ```graphql # extensions/product-discount/input.graphql query Input { cart { lines { quantity merchandise { ... on ProductVariant { id product { hasAnyTag(tags: ["VIP-DISCOUNT"]) } } } } } discountNode { metafield(namespace: "$app:discount-config", key: "percentage") { value } } } ``` ### Step 3: Implement the Function ```typescript // extensions/product-discount/src/run.ts import type { Input, FunctionRunResult } from "../generated/api"; export function run(input: Input): FunctionRunResult { const percentage = parseFloat(input.discountNode?.metafield?.value ?? "0"); if (percentage === 0) return { discounts: [], discountApplicationStrategy: "FIRST" }; const targets = input.cart.lines .filter((line) => line.merchandise.product.hasAnyTag) .map((line) => ({ productVariant: { id: line.merchandise.id } })); return { discounts: [{ targets, value: { percentage: { value: percentage.toString() } }, message: `${percentage}% VIP Discount`, }], discountApplicationStrategy: "FIRST", }; } ``` ### Step 4: Test and Deploy ```bash shopify app function typegen # Generate types from input query shopify app function build # Build to WASM shopify app function run --input test-input.json # Test locally shopify app deploy # Deploy with app ``` See [function-types.md](references/function-types.md) for all function types, [input-output-schemas.md](references/input-output-schemas.md) for I/O shapes, and [wasm-constraints.md](references/wasm-constraints.md) for sandbox limitations. ## Output - WASM binary deployed as a Shopify Function extension - Custom discount/payment/delivery logic running server-side at checkout - Type-safe input/output via generated TypeScript types - Configurable via metafields (merchant-editable without code changes) ## Error Handling | Error | Cause | Solution | |-------|-------|----------| | `FunctionError` | Runtime panic or unhandled exception in WASM | Add error handling; check optional fields for null | | `FUNCTION_TOO_LARGE` | WASM binary exceeds 256KB | Tree-shake deps; use Rust for smaller binaries | | Input query validation | Query references unavailable fields | Match `api_version` to available schema fields | | Timeout (>11ms) | Function exceeds execution limit | Reduce iterations; pre-compute in metafields | ## Examples ### Creating a VIP Discount Function Build a product discount function that applies a configurable percentage off for items tagged "VIP-DISCOUNT" using metafield-driven configuration. See [Function Types](references/function-types.md) for all available function types and their targeting. ### Defining Input Queries and Output Schemas Design the GraphQL input query that declares what cart data your function receives, and return the correctly shaped `FunctionRunResult`. See [Input/Output Schemas](references/input-output-schemas.md) for I/O shapes per function type. ### Working Within WASM Sandbox Limits Your function hits the 11ms execution timeout or 256KB binary size limit. Apply optimization strategies for the constrained WASM environment. See [WASM Constraints](references/wasm-constraints.md) for sandbox limitations and workarounds. ## Resources - [Shopify Functions Overview](https://shopify.dev/docs/apps/build/functions) - [Product Discount Tutorial](https://shopify.dev/docs/apps/build/discounts/build-discount-function) - [Function APIs Reference](https://shopify.dev/docs/api/functions) - [WASM Limitations](https://shopify.dev/docs/apps/build/functions/input-output#limitations) --- Source attribution: jeremylongshore Original project: https://github.com/jeremylongshore/claude-code-plugins-plus-skills/blob/ab85a061f7bcc039dac13ee193de7a4cd4388571/plugins/saas-packs/shopify-pack/skills/shopify-functions/SKILL.md License: MIT License information: https://opensource.org/license/mit Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice MIT License Copyright (c) 2025 Jeremy Longshore Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. # Mega AI Hub resource metadata Creator / publisher: jeremylongshore Original project: https://github.com/jeremylongshore/claude-code-plugins-plus-skills/blob/ab85a061f7bcc039dac13ee193de7a4cd4388571/plugins/saas-packs/shopify-pack/skills/shopify-functions/SKILL.md Attribution basis: Source repository record Fields of work: Marketing, Sales Roles: Business Development, Growth Marketer, Product Marketer, Sales Engineer, Sales Development Rep (SDR) Specialties: API Tools: Shopify Cli Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: 75a1c3a44287a74bc822fdd9a2ade82e97ec453c95a25c2970af51a5d9c77199