Scaffold an Explicit Document to Avoid Error When Creating Indexes in Google Cloud Datastore

When working with Google Cloud Datastore, I would like to design each kind (collection or table) with its own schema and index files:

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$ tree
.
├── index.yml
└── schema.yml

But not every kind has to have something in the index.yml file. So, what to do? Will the index creation command accept an empty index.yml file with zero byte? Let’s give try:

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$ gcloud preview datastore create-indexes index.yml
ERROR: (gcloud.preview.datastore.create-indexes) An error occurred while parsing file: [/home/chao/kind/index.yml]
The file is empty

No, it does not like it. Then, what’s the minimum required? The answer is an explicit document with an empty document content:

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---

The three dashes form a directives end marker line. YAML uses three dashes to separate directives from document content.

When creating indexes with the file, it will proceed without errors or warnings:

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$ gcloud preview datastore create-indexes index.yml
You are about to update the following configurations:
- myproj/index  From: [/home/chao/kind/index.yml]
Do you want to continue (Y/n)?

Therefore, to avoid error, when scaffold an index.yml file for indexing, use an explicit document with an empty document content.