Fail the build when a generated client dependency is not declared

The generated clients load their dependencies from our package.json, and
the set they need changes with the Smithy codegen version. A codegen bump
that adds a dependency would otherwise only break consumers at runtime.

The build now checks every dependency of the generated package.json files
is declared at the root, and prints the `yarn add` line to fix it.

Issue: CLDSRVCLT-19

Author: francoisferrand

README.md

@@ -15,7 +15,8 @@ yarn build
 ```
 
 The generated clients are shipped inside this package and load their dependencies from the root
-`package.json`, so any runtime dependency of a generated client must be declared there as well.
+`package.json`, so any runtime dependency of a generated client must be declared there as well
+(`yarn build` fails otherwise).
 `yarn check:package` packs the build and verifies it installs and loads in a clean consumer.
 
 ### Local testing

package.json

@@ -27,7 +27,8 @@
   },
   "scripts": {
     "clean:build": "rm -rf build dist",
-    "build:smithy": "smithy build && yarn clean:codegen-gitignore",
+    "build:smithy": "smithy build && yarn clean:codegen-gitignore && yarn check:deps",
+    "check:deps": "bash tests/packaging/check-deps.sh",
     "clean:codegen-gitignore": "rm -f build/smithy/*/typescript-codegen/.gitignore",
     "clean:codegen-node-modules": "rm -rf build/smithy/*/typescript-codegen/node_modules",
     "build:generated:backbeatRoutes": "cd build/smithy/cloudserverBackbeatRoutes/typescript-codegen && yarn install && yarn build",

tests/packaging/check-deps.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+# The generated clients are shipped inside this package, so their runtime
+# dependencies must be declared in the root package.json too.
+set -euo pipefail
+
+cd "$(dirname "$0")/../.."
+
+generated=(build/smithy/*/typescript-codegen/package.json)
+
+missing=$(comm -23 \
+    <(jq -r '.dependencies // {} | keys[]' "${generated[@]}" | sort -u) \
+    <(jq -r '.dependencies // {} | keys[]' package.json | sort -u))
+
+if [ -n "$missing" ]; then
+    echo "ERROR: dependencies of the generated clients missing from package.json, add them with:" >&2
+    echo "  yarn add $(for name in $missing; do
+        jq -r --arg n "$name" '.dependencies[$n] // empty | "\($n)@\(.)"' "${generated[@]}" | head -1
+    done | tr '\n' ' ')" >&2
+    exit 1
+fi