Mateusz Sych
96356dc544
snapshot starts from --in (a design or STEP file) with the script on top, as run does, and refuses options it doesn't take; an unknown command id names the closest registered ids.
40 lines
2.2 KiB
Markdown
40 lines
2.2 KiB
Markdown
# The command engine
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Every user-visible action is a **command**: a `CommandSpec` registered in
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`crates/engine/src/cmd/`, with a dotted, lower-case id (`solid.extrude`, `sketch.create`,
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`timeline.rollback`). The toolbar, dialogs, marking menu, S box, scripts, the CLI, the control
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channel and MCP all run commands through `Session::execute(id, params)`. Commands take JSON
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parameters and never open dialogs; a dialog is a front-end form that builds the parameters.
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```rust
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CommandSpec::new("solid.fillet", "Fillet", fillet)
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.at("SOLID", "MODIFY") // toolbar tab and panel ("" = not on the toolbar)
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.icon("fillet") // drawn in code, assets/icons/ui/source/icons.rs
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.key("F") // default shortcut
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.params("edges: [[x,y,z] | {body, index}]; radius: expr; …"),
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```
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`run` is `fn(&mut Session, &Value) -> Result<Value>`, and `enabled` is
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`fn(&Session) -> Result<(), String>`; the error string is the disabled-button tooltip. The
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`params` string is the one-line documentation shown by `solidcraft-cli commands`, MCP's
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`list_commands` and the [command reference](../reference/commands.md).
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A command that changes the design is undoable by default: the session snapshots the document
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before it runs, and a failing command leaves the document unchanged. Feature commands add a
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feature to the timeline and let the document evaluate it; they validate their inputs first
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(units, ranges, references) and return `BadParams` instead of building a broken feature.
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Only the registry's own dotted ids name commands (matched ignoring case); any other id fails
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with `unknown command`, which names up to three close ids: a typo's (`solid.extrud`), or one
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ending in the same word (`file.open`: did you mean `doc.open`?).
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## Adding a command
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1. Add a `CommandSpec` to the right file in `crates/engine/src/cmd/` and implement `run`.
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2. Write engine tests that measure the result: volume, area, and face/edge/vertex counts
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against values you can derive by hand.
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3. The hostile-input test (`hostile_params_never_panic` in `crates/engine/src/tests.rs`) runs
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your command automatically with every documented parameter set to junk. It must return
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errors, never panic.
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4. For UI work, add a scenario (see [Test harnesses](testing.md)).
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