Part of #785: run and command_batch steps can use earlier results

A run (vectorcraft-cli run, the MCP command_batch tool) had no way to use
an id an earlier step returned. A parameter string that is exactly
$N.path or $last.path now takes that value from step N's result
(0-based), e.g. {"id":"$1.id"}; $$ starts a literal $, and a
reference to nothing fails the step. Objects given to a command are now
used as given: an ids element or id that isn't an object id (or an
unresolved reference) fails instead of the command acting on the
selection. text.setRangeStyle styles the selected type object when no
id is given, as text.setStyle does.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/mod.rs

@@ -366,13 +366,23 @@ pub fn color_value(v: &Value) -> Option<Color> {
 
 /// Objects a command targets: explicit `ids` param or the selection.
 pub(crate) fn targets(s: &Session, p: &Value) -> Result<Vec<NodeId>> {
-    if let Some(ids) = ids_param(p, "ids") {
-        return Ok(ids);
+    // Objects given are used as given: a value that isn't an object id fails rather than the
+    // command acting on the selection instead (#785).
+    let object_id = |v: &Value| v.as_u64().map(NodeId).ok_or_else(|| EngineError::Other(format!("object ids are non-negative integers, not {v}")));
+    match p.get("ids").filter(|v| !v.is_null()) {
+        Some(Value::Array(a)) => return a.iter().map(object_id).collect(),
+        Some(v) => return Err(EngineError::Other(format!("`ids` must be an array of object ids, not {v}"))),
+        None => {}
     }
-    if let Some(id) = id_param(p, "id") {
-        return Ok(vec![id]);
+    match p.get("id").filter(|v| !v.is_null()) {
+        Some(v @ Value::Number(_)) => Ok(vec![object_id(v)?]),
+        // A step reference a batch couldn't resolve (other strings are other ids, such as an
+        // effect's).
+        Some(Value::String(r)) if r.starts_with('$') => {
+            Err(EngineError::Other(format!("`id` is the step reference {r:?}, which only `run` and `command_batch` resolve")))
+        }
+        _ => Ok(s.doc()?.selection.objects.clone()),
     }
-    Ok(s.doc()?.selection.objects.clone())
 }
 
 pub(crate) fn ok() -> Result<Value> {

crates/engine/src/cmd/textedit.rs

@@ -27,7 +27,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Character",
             [],
             None,
-            "{id, start?: byte, end?: byte (default: all text), font?, style?, size?: pt, leading?: pt|\"auto\", tracking?, kerning?: 1/1000 em|\"auto\", baselineShift?: pt, hScale?: %, vScale?: %, rotation?: deg, fill?: colour|\"none\", stroke?: colour|\"none\", strokeWidth?: pt, strokeOptions?: {weight?, cap?, join?, miterLimit?, dash?, dashOffset?, alignDashes?} (as stroke.set: the character stroke), underline?, strikethrough?, allCaps?: bool, smallCaps?: bool, position?: \"normal\"|\"superscript\"|\"subscript\" (sizes from Document Setup), features?: [\"dlig\", \"-liga\", …], charAlign?: \"romanBaseline\"|\"emBoxTop\"|\"emBoxCenter\"|\"emBoxBottom\"|\"icfTop\"|\"icfBottom\"} style a character range (runs are split at the range ends) → {id, runs}",
+            "{id? (default: the one selected type object), start?: byte, end?: byte (default: all text), font?, style?, size?: pt, leading?: pt|\"auto\", tracking?, kerning?: 1/1000 em|\"auto\", baselineShift?: pt, hScale?: %, vScale?: %, rotation?: deg, fill?: colour|\"none\", stroke?: colour|\"none\", strokeWidth?: pt, strokeOptions?: {weight?, cap?, join?, miterLimit?, dash?, dashOffset?, alignDashes?} (as stroke.set: the character stroke), underline?, strikethrough?, allCaps?: bool, smallCaps?: bool, position?: \"normal\"|\"superscript\"|\"subscript\" (sizes from Document Setup), features?: [\"dlig\", \"-liga\", …], charAlign?: \"romanBaseline\"|\"emBoxTop\"|\"emBoxCenter\"|\"emBoxBottom\"|\"icfTop\"|\"icfBottom\"} style a character range (runs are split at the range ends) → {id, runs}",
             has_doc,
             set_range_style
         ),
@@ -420,7 +420,14 @@ pub(crate) fn protect_missing_glyphs(before: &[TextRun], runs: &mut Vec<TextRun>
 
 fn set_range_style(s: &mut Session, p: &Value) -> Result<Value> {
     const C: &str = "text.setRangeStyle";
-    let id = id_param(p, "id").ok_or_else(|| bad(C, "missing `id`"))?;
+    // The type object given, else the one selected (#785).
+    let id = match p.get("id").filter(|v| !v.is_null()) {
+        Some(v) => v.as_u64().map(NodeId).ok_or_else(|| bad(C, format!("`id` must be an object id, not {v}")))?,
+        None => match super::typecmd::text_targets(s, &json!({}), C)?.as_slice() {
+            [one] => *one,
+            _ => return Err(bad(C, "missing `id`: give one, or select one type object")),
+        },
+    };
     let change = CharChange::parse(p, C, &s.doc()?.doc.setup)?;
     if change.is_empty() {
         return Err(bad(C, "nothing to change"));

crates/engine/src/lib.rs

@@ -9,6 +9,7 @@
 pub mod cmd;
 pub mod guard;
 pub mod inspect;
+pub mod steps;
 mod tooling;
 pub mod units;
 

crates/engine/src/steps.rs

@@ -0,0 +1,138 @@
+//! References between the steps of a batch (`vectorcraft-cli run`, MCP `command_batch`): a
+//! parameter string that is exactly `$N` or `$N.path` takes that value from the result of step `N`
+//! (0-based, in the order the steps ran), and `$last…` from the step before. A path goes into
+//! objects by key and into arrays by index: `$1.id`, `$2.ids.0`, `$last.ids[0]`. `$$` at the start
+//! of a string stands for one `$` and is never a reference (text such as `$$1.99`). A string that
+//! looks like a reference but names no value is an error, so a step never runs with a reference
+//! left in it.
+
+use serde_json::Value;
+
+/// Most nesting [`resolve`] walks into: deeper parameters are left as they are.
+const MAX_DEPTH: usize = 64;
+
+/// `params` with every step reference replaced from `results` (the results of the steps run so
+/// far, in order); an error names a reference that resolves to nothing.
+pub fn resolve(params: &Value, results: &[Value]) -> Result<Value, String> {
+    resolve_at(params, results, 0)
+}
+
+fn resolve_at(v: &Value, results: &[Value], depth: usize) -> Result<Value, String> {
+    if depth > MAX_DEPTH {
+        return Ok(v.clone());
+    }
+    Ok(match v {
+        Value::String(s) => match s.strip_prefix("$$") {
+            Some(rest) => Value::String(format!("${rest}")),
+            None => match parse(s) {
+                Some((step, path)) => lookup(s, step, &path, results)?,
+                None => v.clone(),
+            },
+        },
+        Value::Array(a) => Value::Array(a.iter().map(|x| resolve_at(x, results, depth + 1)).collect::<Result<_, _>>()?),
+        Value::Object(o) => Value::Object(o.iter().map(|(k, x)| Ok((k.clone(), resolve_at(x, results, depth + 1)?))).collect::<Result<_, String>>()?),
+        _ => v.clone(),
+    })
+}
+
+/// Which step a reference names.
+#[derive(Debug, PartialEq)]
+enum Step {
+    Index(usize),
+    Last,
+}
+
+/// A path segment: an object key or an array index (`.0` is either, as the value decides).
+#[derive(Debug, PartialEq)]
+enum Seg {
+    Key(String),
+    Index(usize),
+}
+
+/// `$N…` or `$last…` → the step and the path after it; `None` for any other string.
+fn parse(s: &str) -> Option<(Step, Vec<Seg>)> {
+    let rest = s.strip_prefix('$')?;
+    let digits = rest.bytes().take_while(u8::is_ascii_digit).count();
+    let (step, mut rest) = if digits > 0 {
+        let (n, rest) = rest.split_at_checked(digits)?;
+        (Step::Index(n.parse().ok()?), rest)
+    } else {
+        (Step::Last, rest.strip_prefix("last")?)
+    };
+    let mut path = vec![];
+    while !rest.is_empty() {
+        if let Some(r) = rest.strip_prefix('.') {
+            let len = r.bytes().take_while(|b| b.is_ascii_alphanumeric() || *b == b'_').count();
+            let (key, r) = r.split_at_checked(len)?;
+            if key.is_empty() {
+                return None;
+            }
+            path.push(Seg::Key(key.to_string()));
+            rest = r;
+        } else {
+            let (n, r) = rest.strip_prefix('[')?.split_once(']')?;
+            path.push(Seg::Index(n.parse().ok()?));
+            rest = r;
+        }
+    }
+    Some((step, path))
+}
+
+fn lookup(text: &str, step: Step, path: &[Seg], results: &[Value]) -> Result<Value, String> {
+    let (i, found) = match step {
+        Step::Index(i) => (i, results.get(i)),
+        Step::Last => (results.len().saturating_sub(1), results.last()),
+    };
+    let mut cur = found.ok_or_else(|| format!("`{text}`: there is no step {i} before this one (steps count from 0; write $$ for a literal $)"))?;
+    for seg in path {
+        let next = match (seg, cur) {
+            (Seg::Key(k), Value::Object(o)) => o.get(k),
+            (Seg::Key(k), Value::Array(a)) => k.parse::<usize>().ok().and_then(|n| a.get(n)),
+            (Seg::Index(n), Value::Array(a)) => a.get(*n),
+            _ => None,
+        };
+        cur = next.ok_or_else(|| format!("`{text}`: step {i}'s result has no such value (write $$ for a literal $)"))?;
+    }
+    Ok(cur.clone())
+}
+
+#[cfg(test)]
+mod tests {
+    use serde_json::json;
+
+    use super::*;
+
+    #[test]
+    fn references_take_values_from_earlier_results() {
+        let results = [json!({"index": 0}), json!({"id": 2}), json!({"ids": [5, 6]})];
+        let p = json!({"id": "$1.id", "ids": ["$2.ids.1", "$last.ids[0]"], "nested": {"all": "$2"}, "n": 3, "flag": true});
+        assert_eq!(resolve(&p, &results).unwrap(), json!({"id": 2, "ids": [6, 5], "nested": {"all": {"ids": [5, 6]}}, "n": 3, "flag": true}));
+    }
+
+    #[test]
+    fn plain_strings_and_escapes_are_left_alone() {
+        let results = [json!({"id": 2})];
+        let p = json!({"text": "costs $1", "price": "$$1.99", "name": "a$1.id", "dollar": "$", "word": "$lastname"});
+        assert_eq!(
+            resolve(&p, &results).unwrap(),
+            json!({"text": "costs $1", "price": "$1.99", "name": "a$1.id", "dollar": "$", "word": "$lastname"})
+        );
+    }
+
+    #[test]
+    fn a_reference_to_nothing_is_an_error() {
+        let results = [json!({"id": 2})];
+        for bad in ["$1", "$1.id", "$0.ids", "$0.id.x", "$last.nope", "$7[0]"] {
+            let e = resolve(&json!({"id": bad}), &results).unwrap_err();
+            assert!(e.contains(bad), "{bad}: {e}");
+        }
+        assert!(resolve(&json!({"id": "$last"}), &[]).is_err(), "no step before the first");
+        // Huge indexes and deep nesting don't panic.
+        assert!(resolve(&json!("$99999999999999999999999.id"), &results).is_ok_and(|v| v == json!("$99999999999999999999999.id")));
+        let mut deep = json!("$0.id");
+        for _ in 0..200 {
+            deep = json!([deep]);
+        }
+        assert!(resolve(&deep, &results).is_ok());
+    }
+}

crates/engine/src/tests.rs

@@ -853,3 +853,30 @@ fn new_layers_and_sublayers_are_numbered_together() {
     let sub = s.execute("layer.newSublayer", &json!({})).unwrap();
     assert_eq!(name(&s, &sub), "Layer 4", "the art doesn't count");
 }
+
+/// #785: objects given are used as given (a value that isn't an object id fails, never the
+/// selection instead), and `text.setRangeStyle` works on the selected type object without `id`.
+#[test]
+fn given_targets_are_used_as_given_and_range_style_takes_the_selected_type() {
+    let mut s = session();
+    let first = s.execute("text.create", &json!({"x": 10, "y": 60, "text": "first", "size": 30})).unwrap()["id"].clone();
+    s.execute("text.create", &json!({"x": 10, "y": 140, "text": "second", "size": 30})).unwrap();
+    for bad in [
+        json!({"id": "$1.id", "size": 60}),
+        json!({"id": 2.5, "size": 60}),
+        json!({"ids": [first.clone(), "$1.id"], "size": 60}),
+        json!({"ids": 3, "size": 60}),
+    ] {
+        assert!(s.execute("text.setStyle", &bad).is_err(), "{bad}");
+    }
+    // Another kind of id (an effect's) is still not an object id.
+    let sel = s.doc().unwrap().selection.objects.clone();
+    assert!(s.execute("effect.apply", &json!({"id": "stylize.dropShadow"})).is_ok());
+    assert_eq!(s.doc().unwrap().selection.objects, sel);
+    // The selected type object (the second) is styled when no id is given.
+    let r = s.execute("text.setRangeStyle", &json!({"start": 0, "end": 3, "style": "Bold"})).unwrap();
+    assert_ne!(r["id"], first);
+    s.execute("select.all", &json!({})).unwrap();
+    assert!(s.execute("text.setRangeStyle", &json!({"start": 0, "end": 3, "size": 40})).is_err(), "two type objects: which one?");
+    assert!(s.execute("text.setRangeStyle", &json!({"id": "two", "size": 40})).is_err());
+}