move prepare_env.py to Python file in mcp-run-python (#1461)

Author: samuelcolvin

.github/workflows/ci.yml

@@ -240,24 +240,11 @@ jobs:
         with:
           deno-version: v2.x
 
-      - run: |
-          deno fmt
-          deno lint
-          deno check src
-        working-directory: mcp-run-python
+      - run: make lint-js
 
       - run: uv run --package mcp-run-python pytest mcp-run-python -v
 
-      # check warmup works
-      - name: warmup
-        run: |
-          deno run \
-            -N \
-            -R=node_modules \
-            -W=node_modules \
-            --node-modules-dir=auto \
-            src/main.ts \
-            warmup
+      - run: deno task dev warmup
         working-directory: mcp-run-python
 
   # https://github.com/marketplace/actions/alls-green#why used for branch protection checks

Makefile

@@ -80,7 +80,7 @@ testcov: test ## Run tests and generate a coverage report
 
 .PHONY: test-mrp
 test-mrp: ## Build and  tests of mcp-run-python
-	cd mcp-run-python && npm run prepare
+	cd mcp-run-python && deno task build
 	uv run --package mcp-run-python pytest mcp-run-python -v
 
 .PHONY: update-examples

mcp-run-python/.gitignore

@@ -1 +1,2 @@
 node_modules
+src/prepareEnvCode.ts

mcp-run-python/README.md

@@ -2,8 +2,8 @@
 
 [Model Context Protocol](https://modelcontextprotocol.io/) server to run Python code in a sandbox.
 
-The code is executed using [Pyodide](https://pyodide.org) in [Deno](https://deno.com/) and is therefore
-isolated from the rest of the operating system.
+The code is executed using [Pyodide](https://pyodide.org) in [Deno](https://deno.com/) and is therefore isolated from
+the rest of the operating system.
 
 **See <https://ai.pydantic.dev/mcp/run-python/> for complete documentation.**
 
@@ -17,20 +17,18 @@ deno run \
 
 where:
 
-- `-N -R=node_modules -W=node_modules` (alias of
-  `--allow-net --allow-read=node_modules --allow-write=node_modules`) allows
-  network access and read+write access to `./node_modules`. These are required
-  so pyodide can download and cache the Python standard library and packages
+- `-N -R=node_modules -W=node_modules` (alias of `--allow-net --allow-read=node_modules --allow-write=node_modules`)
+  allows network access and read+write access to `./node_modules`. These are required so pyodide can download and cache
+  the Python standard library and packages
 - `--node-modules-dir=auto` tells deno to use a local `node_modules` directory
 - `stdio` runs the server with the
-  [Stdio MCP transport](https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/transports/#stdio)
-  — suitable for running the process as a subprocess locally
+  [Stdio MCP transport](https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/transports/#stdio) —
+  suitable for running the process as a subprocess locally
 - `sse` runs the server with the
-  [SSE MCP transport](https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/transports/#http-with-sse)
-  — running the server as an HTTP server to connect locally or remotely
-- `warmup` will run a minimal Python script to download and cache the Python
-  standard library. This is also useful to check the server is running
-  correctly.
+  [SSE MCP transport](https://spec.modelcontextprotocol.io/specification/2024-11-05/basic/transports/#http-with-sse) —
+  running the server as an HTTP server to connect locally or remotely
+- `warmup` will run a minimal Python script to download and cache the Python standard library. This is also useful to
+  check the server is running correctly.
 
 Here's an example of using `@pydantic/mcp-run-python` with PydanticAI:
 

mcp-run-python/build.ts

@@ -0,0 +1,16 @@
+// inline src/prepare_env.py into src/prepareEnvCode.js
+import * as path from '@std/path'
+
+if (!import.meta.dirname) {
+  throw new Error('import.meta.dirname is not defined, unable to load prepare_env.py')
+}
+const src = path.join(import.meta.dirname, 'src/prepare_env.py')
+const dst = path.join(import.meta.dirname, 'src/prepareEnvCode.ts')
+
+let pythonCode = await Deno.readTextFile(src)
+pythonCode = pythonCode.replace(/\\/g, '\\\\')
+const jsCode = `\
+// DO NOT EDIT THIS FILE DIRECTLY, INSTEAD RUN "deno run build"
+export const preparePythonCode = \`${pythonCode}\`
+`
+await Deno.writeTextFile(dst, jsCode)

mcp-run-python/deno.json

@@ -1,17 +1,21 @@
 {
   "name": "@pydantic/mcp-run-python",
-  "version": "0.0.11",
+  "version": "0.0.13",
   "license": "MIT",
   "nodeModulesDir": "auto",
   "exports": {
     ".": "./src/main.ts"
   },
   "tasks": {
-    "lint-format": "deno fmt && deno lint && deno check src"
+    "build": "deno run -R=. -W=src build.ts",
+    "lint-format": "deno task build && deno fmt && deno lint && deno check src && deno publish --dry-run --allow-dirty",
+    "dev": "deno task build && deno run -N -R=node_modules -W=node_modules src/main.ts",
+    "build-publish": "deno task build && deno publish"
   },
   "imports": {
     "@modelcontextprotocol/sdk": "npm:@modelcontextprotocol/sdk@^1.8.0",
     "@std/cli": "jsr:@std/cli@^1.0.15",
+    "@std/path": "jsr:@std/path@^1.0.8",
     "pyodide": "npm:pyodide@^0.27.4",
     "zod": "npm:zod@^3.24.2"
   },
@@ -20,17 +24,15 @@
     "semiColons": false,
     "singleQuote": true,
     "include": [
-      "src/"
+      "."
     ]
   },
-  "compilerOptions": {
-    "types": [
-      "node"
-    ],
-    "lib": [
-      "ESNext",
-      "deno.ns",
-      "dom" // console needs this
+  "publish": {
+    "include": [
+      "src/*.ts",
+      "src/prepareEnvCode.ts", // required to override gitignore
+      "README.md",
+      "deno.json"
     ]
   }
 }

mcp-run-python/deno.lock

@@ -11,7 +11,7 @@ import { z } from 'zod'
 
 import { asXml, runCode } from './runCode.ts'
 
-const VERSION = '0.0.11'
+const VERSION = '0.0.13'
 
 export async function main() {
   const { args } = Deno

mcp-run-python/src/main.ts

@@ -1,4 +1,3 @@
-export const preparePythonCode = `
 """Logic for installing dependencies in Pyodide.
 
 Mostly taken from https://github.com/pydantic/pydantic.run/blob/main/src/frontend/src/prepare_env.py
@@ -162,7 +161,7 @@ def _read_pep723_metadata(code: str) -> dict[str, Any]:
     Copied from https://packaging.python.org/en/latest/specifications/inline-script-metadata/#reference-implementation
     """
     name = 'script'
-    magic_comment_regex = r'(?m)^# /// (?P<type>[a-zA-Z0-9-]+)$\\s(?P<content>(^#(| .*)$\\s)+)^# ///$'
+    magic_comment_regex = r'(?m)^# /// (?P<type>[a-zA-Z0-9-]+)$\s(?P<content>(^#(| .*)$\s)+)^# ///$'
     matches = list(filter(lambda m: m.group('type') == name, re.finditer(magic_comment_regex, code)))
     if len(matches) > 1:
         raise ValueError(f'Multiple {name} blocks found')
@@ -199,4 +198,3 @@ def _find_imports_to_install(imports: list[str]) -> Iterable[str]:
                 yield package_name
             elif '.' not in module:
                 yield module
-`