add support for PATCH_PACKAGE_IGNORE_MISSING env var

Author: andyjy

integration-tests/ignore-missing/__snapshots__/ignore-missing.test.ts.snap

@@ -16,3 +16,12 @@ [email protected] ✔
 Skipping missing [email protected] ✔
 END SNAPSHOT"
 `;
+
+exports[`Test ignore-missing: setting PATCH_PACKAGE_IGNORE_MISSING=1 forces patch-package to return 0 1`] = `
+"SNAPSHOT: setting PATCH_PACKAGE_IGNORE_MISSING=1 forces patch-package to return 0
+patch-package 0.0.0
+Applying patches...
+[email protected] ✔
+Skipping missing [email protected] ✔
+END SNAPSHOT"
+`;

integration-tests/ignore-missing/ignore-missing.sh

@@ -15,3 +15,8 @@ fi
 echo "SNAPSHOT: adding --ignore-missing forces patch-package to return 0"
 patch-package --ignore-missing;
 echo "END SNAPSHOT"
+
+export PATCH_PACKAGE_IGNORE_MISSING=1
+echo "SNAPSHOT: setting PATCH_PACKAGE_IGNORE_MISSING=1 forces patch-package to return 0"
+patch-package;
+echo "END SNAPSHOT"

src/index.ts

@@ -86,7 +86,8 @@ if (argv.version || argv.v) {
 
     const shouldExitWithWarning = !!argv["error-on-warn"]
 
-    const ignoreMissing = !!argv["ignore-missing"]
+    const ignoreMissing =
+      !!argv["ignore-missing"] || !!process.env.PATCH_PACKAGE_IGNORE_MISSING
 
     applyPatchesForApp({
       appPath,
@@ -157,6 +158,13 @@ Usage:
       This is useful when working with monorepos and wanting to install sub-packages
       separately from the root package, with pruned dependencies.
 
+      This option is can also be set via the environment variable
+      PATCH_PACKAGE_IGNORE_MISSING=1. Setting this env variable during the deployment
+      build process is recommended instead of using the --ignore-missing command option
+      when we want to ignore missing packages during deployment (of a monorepo with
+      pruned dependencies), but ensure we fail loudly during development if any
+      dependencies are moved or removed without updating the patches accordingly.
+
       See https://github.com/ds300/patch-package/issues/339 for background.