Reusing an existing Click tool with register_commands#

The register_commands plugin hook lets you add extra sub-commands to the datasette CLI tool.

I have a lot of existing tools that I’d like to also make available as plugins. I figured out this pattern for my git-history tool today:

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from datasette import hookimpl
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from git_history.cli import cli as git_history_cli
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@hookimpl
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def register_commands(cli):
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    cli.add_command(git_history_cli, name="git-history")

Now I can run the following:

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% datasette git-history --help
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Usage: datasette git-history [OPTIONS] COMMAND [ARGS]...
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  Tools for analyzing Git history using SQLite
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Options:
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  --version  Show the version and exit.
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  --help     Show this message and exit.
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Commands:
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  file  Analyze the history of a specific file and write it to SQLite

I initially tried doing this:

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@hookimpl
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def register_commands(cli):
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    cli.command(name="git-history")(git_history_file)

But got the following error:

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TypeError: Attempted to convert a callback into a command twice.

Using cli.add_command() turns out to be the right way to do this.

Research issue for this: datasette#1538.