vegafusion_core/expression/

visitors.rs

use crate::proto::gen::expression::property::Key;
use crate::proto::gen::expression::{
    ArrayExpression, BinaryExpression, CallExpression, ConditionalExpression, Expression,
    Identifier, Literal, LogicalExpression, MemberExpression, ObjectExpression, UnaryExpression,
};

use crate::expression::column_usage::{ColumnUsage, DatasetsColumnUsage, VlSelectionFields};
use crate::expression::supported::{
    ALL_DATA_FNS, ALL_EXPRESSION_CONSTANTS, ALL_SCALE_FNS, IMPLICIT_VARS, SUPPORTED_DATA_FNS,
    SUPPORTED_EXPRESSION_FNS, SUPPORTED_SCALE_FNS,
};
use crate::proto::gen::expression::expression::Expr;
use crate::proto::gen::expression::literal::Value;
use crate::proto::gen::tasks::Variable;
use crate::task_graph::graph::ScopedVariable;
use crate::task_graph::scope::TaskScope;
use crate::task_graph::task::InputVariable;
use std::collections::HashSet;

pub trait ExpressionVisitor {
    fn visit_expression(&mut self, _expression: &Expression) {}
    fn visit_identifier(&mut self, _node: &Identifier) {}
    fn visit_called_identifier(&mut self, _node: &Identifier, _args: &[Expression]) {}
    fn visit_literal(&mut self, _node: &Literal) {}
    fn visit_binary(&mut self, _node: &BinaryExpression) {}
    fn visit_logical(&mut self, _node: &LogicalExpression) {}
    fn visit_unary(&mut self, _node: &UnaryExpression) {}
    fn visit_conditional(&mut self, _node: &ConditionalExpression) {}
    fn visit_member(&mut self, _node: &MemberExpression) {}
    fn visit_call(&mut self, _node: &CallExpression) {}
    fn visit_array(&mut self, _node: &ArrayExpression) {}
    fn visit_object(&mut self, _node: &ObjectExpression) {}
    fn visit_object_key(&mut self, _node: &Key) {}
    fn visit_static_member_identifier(&mut self, _node: &Identifier) {}
}

pub trait MutExpressionVisitor {
    fn visit_expression(&mut self, _expression: &mut Expression) {}
    fn visit_identifier(&mut self, _node: &mut Identifier) {}
    fn visit_called_identifier(&mut self, _node: &mut Identifier, _args: &mut [Expression]) {}
    fn visit_literal(&mut self, _node: &mut Literal) {}
    fn visit_binary(&mut self, _node: &mut BinaryExpression) {}
    fn visit_logical(&mut self, _node: &mut LogicalExpression) {}
    fn visit_unary(&mut self, _node: &mut UnaryExpression) {}
    fn visit_conditional(&mut self, _node: &mut ConditionalExpression) {}
    fn visit_member(&mut self, _node: &mut MemberExpression) {}
    fn visit_call(&mut self, _node: &mut CallExpression) {}
    fn visit_array(&mut self, _node: &mut ArrayExpression) {}
    fn visit_object(&mut self, _node: &mut ObjectExpression) {}
    fn visit_object_key(&mut self, _node: &mut Key) {}
    fn visit_static_member_identifier(&mut self, _node: &mut Identifier) {}
}

/// Visitor to set all spans in the expression tree to None
#[derive(Clone, Default)]
pub struct ClearSpansVisitor {}
impl ClearSpansVisitor {
    pub fn new() -> Self {
        Self {}
    }
}

impl MutExpressionVisitor for ClearSpansVisitor {
    fn visit_expression(&mut self, expression: &mut Expression) {
        expression.span.take();
    }
    fn visit_member(&mut self, node: &mut MemberExpression) {
        node.property.as_mut().unwrap().span.take();
    }
}

/// Visitor to collect all unbound input variables in the expression
#[derive(Clone, Default)]
pub struct GetInputVariablesVisitor {
    pub input_variables: HashSet<InputVariable>,
    pub expression_fns: HashSet<String>,
    pub data_fns: HashSet<String>,
    pub scale_fns: HashSet<String>,
}

impl GetInputVariablesVisitor {
    pub fn new() -> Self {
        Self {
            input_variables: Default::default(),
            expression_fns: Default::default(),
            data_fns: Default::default(),
            scale_fns: Default::default(),
        }
    }
}

impl ExpressionVisitor for GetInputVariablesVisitor {
    fn visit_identifier(&mut self, node: &Identifier) {
        // implicit vars like datum and event do not count as a variables
        if !IMPLICIT_VARS.contains(node.name.as_str())
            && !ALL_EXPRESSION_CONSTANTS.contains(node.name.as_str())
        {
            self.input_variables.insert(InputVariable {
                var: Variable::new_signal(&node.name),
                propagate: true,
            });
        }
    }

    /// Collect data and scale identifiers. These show up as a literal string as the first
    /// argument to a Data or Scale callable.
    fn visit_called_identifier(&mut self, node: &Identifier, args: &[Expression]) {
        if let Some(arg0) = args.first() {
            if let Ok(arg0) = arg0.as_literal() {
                if let Value::String(arg0) = arg0.value() {
                    // Check data callable
                    if ALL_DATA_FNS.contains(node.name.as_str()) {
                        // Propagate on changes to data unless this is a modify function
                        let propagate = node.name != "modify";
                        self.input_variables.insert(InputVariable {
                            var: Variable::new_data(arg0),
                            propagate,
                        });
                    }

                    // Check scale callable
                    if ALL_SCALE_FNS.contains(node.name.as_str()) {
                        self.input_variables.insert(InputVariable {
                            var: Variable::new_scale(arg0),
                            propagate: true,
                        });
                    }
                }
            }
        }

        // Record function type
        if ALL_DATA_FNS.contains(node.name.as_str()) {
            self.data_fns.insert(node.name.clone());
        } else if ALL_SCALE_FNS.contains(node.name.as_str()) {
            self.scale_fns.insert(node.name.clone());
        } else {
            self.expression_fns.insert(node.name.clone());
        }
    }
}

/// Visitor to collect all output variables in the expression
#[derive(Clone, Default)]
pub struct UpdateVariablesExprVisitor {
    pub update_variables: HashSet<Variable>,
}

impl UpdateVariablesExprVisitor {
    pub fn new() -> Self {
        Self {
            update_variables: Default::default(),
        }
    }
}

impl ExpressionVisitor for UpdateVariablesExprVisitor {
    fn visit_called_identifier(&mut self, node: &Identifier, args: &[Expression]) {
        if node.name == "modify" {
            if let Some(arg0) = args.first() {
                if let Ok(arg0) = arg0.as_literal() {
                    if let Value::String(arg0) = arg0.value() {
                        // First arg is a string, which holds the name of the output dataset
                        self.update_variables.insert(Variable::new_data(arg0));
                    }
                }
            }
        }
    }
}

/// Visitor to check whether an expression is supported by the VegaFusion Runtime
#[derive(Clone, Default)]
pub struct CheckSupportedExprVisitor {
    pub supported: bool,
}

impl CheckSupportedExprVisitor {
    pub fn new() -> Self {
        Self { supported: true }
    }
}

impl ExpressionVisitor for CheckSupportedExprVisitor {
    fn visit_called_identifier(&mut self, node: &Identifier, args: &[Expression]) {
        // Check for unsupported functions
        if ALL_DATA_FNS.contains(node.name.as_str()) {
            if !SUPPORTED_DATA_FNS.contains(node.name.as_str()) {
                self.supported = false;
            }
            if node.name == "vlSelectionResolve" && args.len() > 2 {
                // The third (multi) and forth (vl5) arguments are not supported
                self.supported = false;
            }
        } else if ALL_SCALE_FNS.contains(node.name.as_str()) {
            if !SUPPORTED_SCALE_FNS.contains(node.name.as_str()) {
                self.supported = false;
            }
        } else if !SUPPORTED_EXPRESSION_FNS.contains(node.name.as_str()) {
            self.supported = false;
        } else if node.name == "indexof" {
            // We only support the array variant of indexof (not the string variant)
            if !(args.len() == 2 && matches!(args[0].expr, Some(Expr::Array(_)))) {
                self.supported = false;
            }
        } else if node.name == "format" {
            // We only support format with an empty string as second argument
            if args.len() != 2 {
                self.supported = false;
            } else if let Some(Expr::Literal(Literal {
                value: Some(Value::String(v)),
                ..
            })) = &args[1].expr
            {
                if !v.is_empty() {
                    self.supported = false;
                }
            } else {
                self.supported = false;
            }
        }
    }

    fn visit_member(&mut self, node: &MemberExpression) {
        // Check for unsupported use of member property.
        // Property cannot use implicit datum variable
        if node.computed {
            let property = node.property.as_ref().unwrap();
            if property.implicit_vars().contains(&"datum".to_string()) {
                // e.g. ([0, 1])[datum.foo]
                self.supported = false;
            }
        }

        if let Some(object) = &node.object {
            if object.implicit_vars().contains(&"datum".to_string()) {
                let object_expr = object.expr.as_ref().unwrap();
                let property = node.property.as_ref().unwrap();
                let property_expr = property.expr.as_ref().unwrap();

                // Object of member may only contain datum if it is the literal datum identifier.
                // datum["foo"] is ok, (datum["foo"])["bar"] is not
                let is_datum_literal = object_expr
                    == &Expr::Identifier(Identifier {
                        name: "datum".to_string(),
                    });

                // ... unless the property is a number. datum["foo"][0] is ok
                let is_number_index = matches!(
                    property_expr,
                    Expr::Literal(Literal {
                        value: Some(Value::Number(_)),
                        ..
                    })
                );

                if !(is_datum_literal || is_number_index) {
                    self.supported = false;
                }
            }
        }
    }
}

/// Visitor to collect all implicit variables used in an expression
#[derive(Clone, Default)]
pub struct ImplicitVariablesExprVisitor {
    pub implicit_vars: HashSet<String>,
}

impl ImplicitVariablesExprVisitor {
    pub fn new() -> Self {
        Self {
            implicit_vars: Default::default(),
        }
    }
}

impl ExpressionVisitor for ImplicitVariablesExprVisitor {
    fn visit_identifier(&mut self, node: &Identifier) {
        // implicit vars like datum and event do not count as a variables
        if IMPLICIT_VARS.contains(node.name.as_str()) {
            self.implicit_vars.insert(node.name.clone());
        }
    }
}

/// Visitor to collect the columns
#[derive(Clone)]
pub struct DatasetsColumnUsageVisitor<'a> {
    pub vl_selection_fields: &'a VlSelectionFields,
    pub datum_var: &'a Option<ScopedVariable>,
    pub usage_scope: &'a [u32],
    pub task_scope: &'a TaskScope,
    pub dataset_column_usage: DatasetsColumnUsage,
}

impl<'a> DatasetsColumnUsageVisitor<'a> {
    pub fn new(
        datum_var: &'a Option<ScopedVariable>,
        usage_scope: &'a [u32],
        task_scope: &'a TaskScope,
        vl_selection_fields: &'a VlSelectionFields,
    ) -> Self {
        Self {
            vl_selection_fields,
            datum_var,
            usage_scope,
            task_scope,
            dataset_column_usage: DatasetsColumnUsage::empty(),
        }
    }
}

impl ExpressionVisitor for DatasetsColumnUsageVisitor<'_> {
    fn visit_member(&mut self, node: &MemberExpression) {
        if let (Some(datum_var), Some(object), Some(property)) =
            (&self.datum_var, &node.object, &node.property)
        {
            if let (Some(Expr::Identifier(object_id)), Some(property_expr)) =
                (&object.expr, &property.expr)
            {
                if object_id.name == "datum" {
                    // This expression is a member expression on the datum free variable
                    if node.computed {
                        match property_expr {
                            Expr::Literal(Literal {
                                value: Some(Value::String(name)),
                                ..
                            }) => {
                                // Found `datum['col_name']` usage
                                self.dataset_column_usage = self
                                    .dataset_column_usage
                                    .with_column_usage(datum_var, ColumnUsage::from(name.as_str()));
                            }
                            _ => {
                                // Unknown usage (e.g. `datum['col_' + 'name']`)
                                self.dataset_column_usage =
                                    self.dataset_column_usage.with_unknown_usage(datum_var);
                            }
                        }
                    } else {
                        match property_expr {
                            Expr::Identifier(id) => {
                                // Found `datum.col_name` usage
                                self.dataset_column_usage =
                                    self.dataset_column_usage.with_column_usage(
                                        datum_var,
                                        ColumnUsage::from(id.name.as_str()),
                                    );
                            }
                            _ => {
                                // Unknown datum usage
                                self.dataset_column_usage =
                                    self.dataset_column_usage.with_unknown_usage(datum_var);
                            }
                        }
                    }
                }
            }
        }
    }

    fn visit_call(&mut self, node: &CallExpression) {
        // Handle data functions
        if ALL_DATA_FNS.contains(node.callee.as_str()) {
            // First argument should be a string
            if let Some(Expression {
                expr:
                    Some(Expr::Literal(Literal {
                        value: Some(Value::String(reference_data_name)),
                        ..
                    })),
                ..
            }) = node.arguments.first()
            {
                // Resolve data variable
                let reference_data_var = Variable::new_data(reference_data_name);
                if let Ok(resolved) = self
                    .task_scope
                    .resolve_scope(&reference_data_var, self.usage_scope)
                {
                    let scoped_reference_data_var: ScopedVariable = (resolved.var, resolved.scope);
                    // e.g. data('other_dataset')
                    // We don't know which columns in the referenced dataset are used
                    self.dataset_column_usage = self
                        .dataset_column_usage
                        .with_unknown_usage(&scoped_reference_data_var);

                    // Handle vlSelectionTest, which also uses datum columns
                    if let Some(datum_var) = self.datum_var {
                        match node.callee.as_str() {
                            "vlSelectionTest" => {
                                if let Some(fields) =
                                    self.vl_selection_fields.get(&scoped_reference_data_var)
                                {
                                    // Add selection fields to usage for datum
                                    self.dataset_column_usage = self
                                        .dataset_column_usage
                                        .with_column_usage(datum_var, fields.clone());
                                } else {
                                    // Unknown fields dataset, so we don't know which datum columns
                                    // are needed at runtime
                                    self.dataset_column_usage =
                                        self.dataset_column_usage.with_unknown_usage(datum_var);
                                }
                            }
                            "vlSelectionIdTest" => {
                                // Add _vgsid_ fields usage for datum
                                self.dataset_column_usage = self
                                    .dataset_column_usage
                                    .with_column_usage(datum_var, ColumnUsage::from("_vgsid_"));
                            }
                            _ => {}
                        }
                    }
                } else {
                    // Unknown brushing dataset, so we don't know which datum columns
                    // are needed at runtime
                    if let Some(datum_var) = self.datum_var {
                        self.dataset_column_usage =
                            self.dataset_column_usage.with_unknown_usage(datum_var);
                    }
                }
            }
        } else if node.callee.as_str() == "intersect" {
            // Look for expression like:
            //     intersect(arg0, {markname: "view_10_marks"}, ...)
            // In this case "view_10_marks" is the name of a mark dataset, and we don't know what columns
            // from the mark's source dataset are used.
            if let Some(Expression {
                expr: Some(Expr::Object(arg1)),
                ..
            }) = node.arguments.get(1)
            {
                for prop in &arg1.properties {
                    if let (Some(key), Some(val)) = (&prop.key, &prop.value) {
                        let property = match key {
                            Key::Identifier(id) => id.name.clone(),
                            Key::Literal(Literal {
                                value: Some(Value::String(name)),
                                ..
                            }) => name.clone(),
                            _ => continue,
                        };
                        if property == "markname" {
                            if let Some(Expr::Literal(Literal {
                                value: Some(Value::String(mark_name)),
                                ..
                            })) = &val.expr
                            {
                                let mark_data_var = Variable::new_data(mark_name);
                                if let Ok(resolved) = self
                                    .task_scope
                                    .resolve_scope(&mark_data_var, self.usage_scope)
                                {
                                    let scoped_reference_data_var: ScopedVariable =
                                        (resolved.var, resolved.scope);
                                    self.dataset_column_usage = self
                                        .dataset_column_usage
                                        .with_unknown_usage(&scoped_reference_data_var);
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}