Implement a prereqCmd option for installing system deps

closes #101

Author: dschep

README.md

@@ -113,6 +113,16 @@ custom:
     pythonBin: /opt/python3.6/bin/python
 ```
 
+### Run Custom extra packaging scripts
+As a convenience method for if you need to install system dependencies for your python package you
+can specify a command to do so. It honors the `dockerizePip` command so you can `yum install`
+anything available in Amazon Linux if using that option. Example config:
+```yaml
+custom:
+  pythonRequirements:
+    prereqCmd: bash -c "yum install mysql-devel && cp /usr/lib64/mysql/libmysqlclient.so.18.0.0 ./libmysqlclient.so.18"
+```
+
 ## Manual invocations
 
 The `.requirements` and `requirements.zip`(if using zip support) files are left

example/prereq

@@ -0,0 +1,2 @@
+#!/bin/bash
+echo foobar > foobar

example/serverless.yml

@@ -11,6 +11,7 @@ custom:
     zip: false
     cleanupZipHelper: true
     dockerizePip: false
+    prereqCmd: null
 
 package:
   exclude:

index.js

@@ -5,6 +5,7 @@ const BbPromise = require('bluebird');
 const fse = require('fs-extra');
 const {addVendorHelper, removeVendorHelper, packRequirements} = require('./lib/zip');
 const {installRequirements} = require('./lib/pip');
+const {runPrereqCmd} = require('./lib/prereqCmd');
 const {pipfileToRequirements} = require('./lib/pipenv');
 const {linkRequirements, unlinkRequirements} = require('./lib/link');
 const {cleanup} = require('./lib/clean');
@@ -30,6 +31,7 @@ class ServerlessPythonRequirements {
       dockerizePip: false,
       dockerImage: `lambci/lambda:build-${this.serverless.service.provider.runtime}`,
       pipCmdExtraArgs: [],
+      prereqCmd: null,
       noDeploy: [
         'boto3',
         'botocore',
@@ -80,6 +82,7 @@ class ServerlessPythonRequirements {
       .then(pipfileToRequirements)
       .then(addVendorHelper)
       .then(installRequirements)
+      .then(runPrereqCmd)
       .then(packRequirements)
       .then(linkRequirements);
 
@@ -105,6 +108,7 @@ class ServerlessPythonRequirements {
       'requirements:install:install': () => BbPromise.bind(this)
         .then(pipfileToRequirements)
         .then(addVendorHelper)
+        .then(runPrereqCmd)
         .then(installRequirements)
         .then(packRequirements),
       'requirements:clean:clean': () => BbPromise.bind(this)

lib/prereqCmd.js

@@ -0,0 +1,45 @@
+const fse = require('fs-extra');
+const path = require('path');
+const {spawnSync} = require('child_process');
+
+/**
+ * run a prerequisite script if provided
+ * @return {Promise}
+ */
+function runPrereqCmd() {
+  const {prereqCmd} = this.options;
+  this.serverless.cli.log(`Running prerequisite script: ${prereqCmd}`);
+  if (!prereqCmd)
+    return;
+  this.serverless.cli.log(`Running prerequisite script: ${prereqCmd}`);
+  let options = [];
+  if (this.options.dockerizePip) {
+    cmd = 'docker';
+    options = [
+      'run', '--rm',
+      '-v', `${this.servicePath}:/var/task:z`,
+      prereqCmd,
+    ];
+    if (process.platform === 'linux')
+      options.push('-u', `${process.getuid()}:${process.getgid()}`);
+    options.push(this.options.dockerImage);
+    options.push(...pipCmd);
+  } else {
+    cmd = prereqCmd;
+  }
+  const res = spawnSync(cmd, options, {cwd: this.servicePath});
+  if (res.error) {
+    if (res.error.code === 'ENOENT') {
+      if (this.options.dockerizePip) {
+        throw new Error('docker not found! Please install it.');
+      } else {
+        throw new Error(`${prereqCmd} not found!`);
+      }
+    }
+    throw new Error(res.error);
+  }
+  if (res.status != 0)
+    throw new Error(res.stderr);
+};
+
+module.exports = {runPrereqCmd};

test.bats

@@ -14,6 +14,7 @@ setup() {
 teardown() {
     sls requirements clean
     rm -rf puck node_modules
+    rm -f foobar
     if [ -f serverless.yml.bak ]; then mv serverless.yml.bak serverless.yml; fi
 }
 
@@ -148,3 +149,10 @@ teardown() {
     unzip .serverless/sls-py-req-test.zip -d puck
     ls puck/.requirements.zip puck/unzip_requirements.py
 }
+
+@test "py3.6 runs prereq script" {
+    sed -i'.bak' -e 's;prereqCmd: *null;prereqCmd: ./prereq;' serverless.yml
+    sls package
+    unzip .serverless/sls-py-req-test.zip -d puck
+    ls foobar
+}