The Stripe CLI is a developer tool to help you build, test, and manage your integration with Stripe directly from the command line. It interacts with most of Stripe API. It's written in go and is compiled into a binary for distribution.
Its functionality is organized into individual command files, found in pkg/cmd. Most files correspond to a command that can be run via the CLI. For example, the stripe login command is powered by pkg/cmd/login.go (which exposes logic from the login package in pkg/login). pkg/cmd also includes some test files (e.g. pkg/cmd/open_test.go has the tests for pkg/cmd/open.go, per language convention). Some commands have further subcommands, which are defined in a folder under pkg/cmd. For instance, pkg/cmd/plugin.go only serves to collect the sub-commands in pkg/cmd/plugins/*.go (such as stripe plugin install).
The CLI uses the Cobra library for command structure and Viper for flag parsing. Commands are registered in pkg/cmd/root.go in the init function (look for the big rootCmd.AddCommand(...) block). If a command isn't registered there, it'll give an error when invoked from the CLI (e.g. stripe missing_command gives an "unknown command" error).
root.go's Execute function handles actually invoking Cobra, via the rootCmd.ExecuteContext function. CLI input is parsed and routed to the appropriate command, which runs and/or errors accordingly. If there's an error, Execute may print additional help text before exiting.
In addition to the handwritten commands, the CLI also has many auto-generated resources that correspond to base API resources. These commands are registered in pkg/cmd/resources_cmds.go, calling the generic NewNamespaceCmd function for each resource. These auto-generated commands hold no functionality on their own and mostly rely on operation commands to do anything (see below).
The big list of commands found in resources_cmds.go is iself is an auto-generated file. It's built by running pkg/gen/gen_resource_cmds.go, which gets a big list of resources from OpenAPI via api/openapi-spec/spec3.sdk.json and generates the big command file via the pkg/gen/resources_cmds.go.tpl template. Generated commands can be manually overridden, as we do with pkg/cmd/resource/events.go taking precedence over the generated events command.
Under each generated resource are a set of operation commands, corresponding to CRUD operations for that resource (retrieve, create, etc). They are also registered in resources_cmds.go, but use the NewOperationCmd method to build a generic HTTP call and response. These sub-commands are only used for resources.
HTTP requests to the Stripe API are routed through the requests package, starting in pkg/requests/base.go. Under the hood, they use an instance of pkg/stripe/client.go's Client and it's PerformRequest method (which wraps native go HTTP code).