cedar_policy_validator/cedar_schema/
fmt.rs

/*
 * Copyright Cedar Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

//! `Display` implementations for formatting a [`json_schema::Fragment`] in the
//! Cedar schema syntax

use std::{collections::HashSet, fmt::Display};

use itertools::Itertools;
use miette::Diagnostic;
use nonempty::NonEmpty;
use thiserror::Error;

use crate::{json_schema, RawName};
use cedar_policy_core::{ast::InternalName, impl_diagnostic_from_method_on_nonempty_field};

impl<N: Display> Display for json_schema::Fragment<N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for (ns, def) in &self.0 {
            match ns {
                None => write!(f, "{def}")?,
                Some(ns) => write!(f, "{}namespace {ns} {{\n{}}}\n", def.annotations, def)?,
            }
        }
        Ok(())
    }
}

impl<N: Display> Display for json_schema::NamespaceDefinition<N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for (n, ty) in &self.common_types {
            writeln!(f, "{}type {n} = {};", ty.annotations, ty.ty)?
        }
        for (n, ty) in &self.entity_types {
            writeln!(f, "{}entity {n}{};", ty.annotations, ty)?
        }
        for (n, a) in &self.actions {
            writeln!(f, "{}action \"{}\"{};", a.annotations, n.escape_debug(), a)?
        }
        Ok(())
    }
}

impl<N: Display> Display for json_schema::Type<N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            json_schema::Type::Type { ty, .. } => match ty {
                json_schema::TypeVariant::Boolean => write!(f, "__cedar::Bool"),
                json_schema::TypeVariant::Entity { name } => write!(f, "{name}"),
                json_schema::TypeVariant::EntityOrCommon { type_name } => {
                    write!(f, "{type_name}")
                }
                json_schema::TypeVariant::Extension { name } => write!(f, "__cedar::{name}"),
                json_schema::TypeVariant::Long => write!(f, "__cedar::Long"),
                json_schema::TypeVariant::Record(rty) => write!(f, "{rty}"),
                json_schema::TypeVariant::Set { element } => write!(f, "Set < {element} >"),
                json_schema::TypeVariant::String => write!(f, "__cedar::String"),
            },
            json_schema::Type::CommonTypeRef { type_name, .. } => write!(f, "{type_name}"),
        }
    }
}

impl<N: Display> Display for json_schema::RecordType<N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{{")?;
        for (i, (n, ty)) in self.attributes.iter().enumerate() {
            write!(
                f,
                "{}\"{}\"{}: {}",
                ty.annotations,
                n.escape_debug(),
                if ty.required { "" } else { "?" },
                ty.ty
            )?;
            if i < (self.attributes.len() - 1) {
                writeln!(f, ", ")?;
            }
        }
        write!(f, "}}")?;
        Ok(())
    }
}

fn fmt_non_empty_slice<T: Display>(
    f: &mut std::fmt::Formatter<'_>,
    (head, tail): (&T, &[T]),
) -> std::fmt::Result {
    write!(f, "[{head}")?;
    for e in tail {
        write!(f, ", {e}")?;
    }
    write!(f, "]")
}

impl<N: Display> Display for json_schema::EntityType<N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        if let Some(non_empty) = self.member_of_types.split_first() {
            write!(f, " in ")?;
            fmt_non_empty_slice(f, non_empty)?;
        }

        let ty = &self.shape;
        // Don't print `= { }`
        if !ty.is_empty_record() {
            write!(f, " = {ty}")?;
        }

        if let Some(tags) = &self.tags {
            write!(f, " tags {tags}")?;
        }

        Ok(())
    }
}

impl<N: Display> Display for json_schema::ActionType<N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        if let Some(parents) = self.member_of.as_ref().and_then(|refs| refs.split_first()) {
            write!(f, " in ")?;
            fmt_non_empty_slice(f, parents)?;
        }
        if let Some(spec) = &self.applies_to {
            match (
                spec.principal_types.split_first(),
                spec.resource_types.split_first(),
            ) {
                // One of the lists is empty
                // This can only be represented by the empty action
                // This implies an action group
                (None, _) | (_, None) => {
                    write!(f, "")?;
                }
                // Both list are non empty
                (Some(ps), Some(rs)) => {
                    write!(f, " appliesTo {{")?;
                    write!(f, "\n  principal: ")?;
                    fmt_non_empty_slice(f, ps)?;
                    write!(f, ",\n  resource: ")?;
                    fmt_non_empty_slice(f, rs)?;
                    write!(f, ",\n  context: {}", &spec.context.0)?;
                    write!(f, "\n}}")?;
                }
            }
        }
        // No `appliesTo` key: action does not apply to anything
        Ok(())
    }
}

/// Error converting a schema to the Cedar syntax
#[derive(Debug, Diagnostic, Error)]
pub enum ToCedarSchemaSyntaxError {
    /// Collisions between names prevented the conversion to the Cedar syntax
    #[diagnostic(transparent)]
    #[error(transparent)]
    NameCollisions(#[from] NameCollisionsError),
}

/// Duplicate names were found in the schema
//
// This is NOT a publicly exported error type.
#[derive(Debug, Error)]
#[error("There are name collisions: [{}]", .names.iter().join(", "))]
pub struct NameCollisionsError {
    /// Names that had collisions
    names: NonEmpty<InternalName>,
}

impl Diagnostic for NameCollisionsError {
    impl_diagnostic_from_method_on_nonempty_field!(names, loc);
}

impl NameCollisionsError {
    /// Get the names that had collisions
    pub fn names(&self) -> impl Iterator<Item = &InternalName> {
        self.names.iter()
    }
}

/// Convert a [`json_schema::Fragment`] to a string containing the Cedar schema syntax
///
/// As of this writing, this existing code throws an error if any
/// fully-qualified name in a non-empty namespace is a valid common type and
/// also a valid entity type.
//
// Two notes:
// 1) This check is more conservative than necessary. Schemas are allowed to
// shadow an entity type with a common type declaration in the same namespace;
// see RFCs 24 and 70. What the Cedar syntax can't express is if, in that
// situation, we then specifically refer to the shadowed entity type name.  But
// it's harder to walk all type references than it is to walk all type
// declarations, so the conservative code here is fine; we can always make it
// less conservative in the future without breaking people.
// 2) This code is also likely the cause of #1063; see that issue
pub fn json_schema_to_cedar_schema_str<N: Display>(
    json_schema: &json_schema::Fragment<N>,
) -> Result<String, ToCedarSchemaSyntaxError> {
    let mut name_collisions: Vec<InternalName> = Vec::new();
    for (name, ns) in json_schema.0.iter().filter(|(name, _)| !name.is_none()) {
        let entity_types: HashSet<InternalName> = ns
            .entity_types
            .keys()
            .map(|ty_name| {
                RawName::new_from_unreserved(ty_name.clone()).qualify_with_name(name.as_ref())
            })
            .collect();
        let common_types: HashSet<InternalName> = ns
            .common_types
            .keys()
            .map(|ty_name| {
                RawName::new_from_unreserved(ty_name.clone().into())
                    .qualify_with_name(name.as_ref())
            })
            .collect();
        name_collisions.extend(entity_types.intersection(&common_types).cloned());
    }
    if let Some(non_empty_collisions) = NonEmpty::from_vec(name_collisions) {
        return Err(NameCollisionsError {
            names: non_empty_collisions,
        }
        .into());
    }
    Ok(json_schema.to_string())
}

#[cfg(test)]
mod tests {
    use cedar_policy_core::extensions::Extensions;

    use crate::cedar_schema::parser::parse_cedar_schema_fragment;

    #[track_caller]
    fn test_round_trip(src: &str) {
        let (cedar_schema, _) =
            parse_cedar_schema_fragment(src, Extensions::none()).expect("should parse");
        let printed_cedar_schema = cedar_schema.to_cedarschema().expect("should convert");
        let (parsed_cedar_schema, _) =
            parse_cedar_schema_fragment(&printed_cedar_schema, Extensions::none())
                .expect("should parse");
        assert_eq!(cedar_schema, parsed_cedar_schema);
    }

    #[test]
    fn rfc_example() {
        let src = "entity User = {
            jobLevel: Long,
          } tags Set<String>;
          entity Document = {
            owner: User,
          } tags Set<String>;";
        test_round_trip(src);
    }

    #[test]
    fn annotations() {
        let src = r#"@doc("this is the namespace")
namespace TinyTodo {
    @doc("a common type representing a task")
    type Task = {
        @doc("task id")
        "id": Long,
        "name": String,
        "state": String,
    };
    @doc("a common type representing a set of tasks")
    type Tasks = Set<Task>;

    @doc("an entity type representing a list")
    @docComment("any entity type is a child of type `Application`")
    entity List in [Application] = {
        @doc("editors of a list")
        "editors": Team,
        "name": String,
        "owner": User,
        @doc("readers of a list")
        "readers": Team,
        "tasks": Tasks,
    };

    @doc("actions that a user can operate on a list")
    action DeleteList, GetList, UpdateList appliesTo {
        principal: [User],
        resource: [List]
    };
}"#;
        test_round_trip(src);
    }
}
cedar_policy_validator/cedar_schema/fmt.rs

cedar_policy_validator/cedar_schema/
fmt.rs
