Merge bitcoin/bitcoin#19762: rpc: Allow named and positional arguments to be used together

d8b12a75dbfdc1d3e62352f0fa815bbbdc685caf rpc: Allow named and positional arguments to be used together (Ryan Ofsky)

Pull request description:

  It's nice to be able to use named options and positional arguments together.

  Most shell tools accept both, and python functions combine options and arguments allowing them to be passed with even more flexibility. This change adds support for python's approach so as a motivating example:

  ```sh
  bitcoin-cli -named createwallet wallet_name=mywallet load_on_startup=1
  ```

  Can be shortened to:

  ```sh
  bitcoin-cli -named createwallet mywallet load_on_startup=1
  ```

  JSON-RPC standard doesn't have a convention for passing named and positional parameters together, so this implementation makes one up and interprets any unused `"args"` named parameter as a positional parameter array.

  This change is backwards compatible. It doesn't change the interpretation of any previously valid calls, just treats some previously invalid calls as valid.

  Another use case even if you only occasionally use named arguments is that you can define an alias:

  ```
  alias bcli='bitcoin-cli -named'
  ```

  And now use both named named and unnamed arguments from the same alias without having to manually add `-named` option for named arguments or see annoying error "No '=' in named argument... this needs to be present for every argument (even if it is empty)`" for unnamed arguments

ACKs for top commit:
  achow101:
    ACK d8b12a75dbfdc1d3e62352f0fa815bbbdc685caf
  stickies-v:
    re-ACK d8b12a75d
  aureleoules:
    re-ACK d8b12a75dbfdc1d3e62352f0fa815bbbdc685caf

Tree-SHA512: 0cff8b50f584bcbbd376624adccf40536566ed8d1bcd6c88ad565dbc208f19d5e7a48c994efd6329d42b560149340d330397278f08a2912af5f3418d8c8837a9

1 files changed, 22 insertions, 0 deletions

diff --git a/doc/JSON-RPC-interface.md b/doc/JSON-RPC-interface.md
index 12807bfb86..ab5db58cdd 100644
--- a/doc/JSON-RPC-interface.md
+++ b/doc/JSON-RPC-interface.md
@@ -5,6 +5,28 @@ The headless daemon `bitcoind` has the JSON-RPC API enabled by default, the GUI
 option. In the GUI it is possible to execute RPC methods in the Debug Console
 Dialog.
 
+## Parameter passing
+
+The JSON-RPC server supports both _by-position_ and _by-name_ [parameter
+structures](https://www.jsonrpc.org/specification#parameter_structures)
+described in the JSON-RPC specification. For extra convenience, to avoid the
+need to name every parameter value, all RPC methods accept a named parameter
+called `args`, which can be set to an array of initial positional values that
+are combined with named values.
+
+Examples:
+
+```sh
+# "params": ["mywallet", false, false, "", false, false, true]
+bitcoin-cli createwallet mywallet false false "" false false true
+
+# "params": {"wallet_name": "mywallet", "load_on_startup": true}
+bitcoin-cli -named createwallet wallet_name=mywallet load_on_startup=true
+
+# "params": {"args": ["mywallet"], "load_on_startup": true}
+bitcoin-cli -named createwallet mywallet load_on_startup=true
+```
+
 ## Versioning
 
 The RPC interface might change from one major version of Bitcoin Core to the