node-translator.h

// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
// Licensed under the MIT License:
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// THE SOFTWARE.

#ifndef CAPNP_COMPILER_NODE_TRANSLATOR_H_
#define CAPNP_COMPILER_NODE_TRANSLATOR_H_

#include <capnp/orphan.h>
#include <capnp/compiler/grammar.capnp.h>
#include <capnp/schema.capnp.h>
#include <capnp/dynamic.h>
#include <kj/vector.h>
#include <kj/one-of.h>
#include "error-reporter.h"

namespace capnp {
namespace compiler {

class NodeTranslator {
  // Translates one node in the schema from AST form to final schema form.  A "node" is anything
  // that has a unique ID, such as structs, enums, constants, and annotations, but not fields,
  // unions, enumerants, or methods (the latter set have 16-bit ordinals but not 64-bit global IDs).

public:
  class Resolver {
    // Callback class used to find other nodes relative to this one.
    //
    // TODO(cleanup): This has evolved into being a full interface for traversing the node tree.
    //   Maybe we should rename it as such, and move it out of NodeTranslator. See also
    //   TODO(cleanup) on NodeTranslator::BrandedDecl.

  public:
    struct ResolvedDecl {
      uint64_t id;
      uint genericParamCount;
      uint64_t scopeId;
      Declaration::Which kind;
      Resolver* resolver;

      kj::Maybe<schema::Brand::Reader> brand;
      // If present, then it is necessary to replace the brand scope with the given brand before
      // using the target type. This happens when the decl resolved to an alias; all other fields
      // of `ResolvedDecl` refer to the target of the alias, except for `scopeId` which is the
      // scope that contained the alias.
    };

    struct ResolvedParameter {
      uint64_t id;  // ID of the node declaring the parameter.
      uint index;   // Index of the parameter.
    };

    typedef kj::OneOf<ResolvedDecl, ResolvedParameter> ResolveResult;

    virtual kj::Maybe<ResolveResult> resolve(kj::StringPtr name) = 0;
    // Look up the given name, relative to this node, and return basic information about the
    // target.

    virtual kj::Maybe<ResolveResult> resolveMember(kj::StringPtr name) = 0;
    // Look up a member of this node.

    virtual ResolvedDecl resolveBuiltin(Declaration::Which which) = 0;
    virtual ResolvedDecl resolveId(uint64_t id) = 0;

    virtual kj::Maybe<ResolvedDecl> getParent() = 0;
    // Returns the parent of this scope, or null if this is the top scope.

    virtual ResolvedDecl getTopScope() = 0;
    // Get the top-level scope containing this node.

    virtual kj::Maybe<Schema> resolveBootstrapSchema(uint64_t id, schema::Brand::Reader brand) = 0;
    // Get the schema for the given ID.  If a schema is returned, it must be safe to traverse its
    // dependencies via the Schema API.  A schema that is only at the bootstrap stage is
    // acceptable.
    //
    // Throws an exception if the id is not one that was found by calling resolve() or by
    // traversing other schemas.  Returns null if the ID is recognized, but the corresponding
    // schema node failed to be built for reasons that were already reported.

    virtual kj::Maybe<schema::Node::Reader> resolveFinalSchema(uint64_t id) = 0;
    // Get the final schema for the given ID.  A bootstrap schema is not acceptable.  A raw
    // node reader is returned rather than a Schema object because using a Schema object built
    // by the final schema loader could trigger lazy initialization of dependencies which could
    // lead to a cycle and deadlock.
    //
    // Throws an exception if the id is not one that was found by calling resolve() or by
    // traversing other schemas.  Returns null if the ID is recognized, but the corresponding
    // schema node failed to be built for reasons that were already reported.

    virtual kj::Maybe<ResolvedDecl> resolveImport(kj::StringPtr name) = 0;
    // Get the ID of an imported file given the import path.

    virtual kj::Maybe<Type> resolveBootstrapType(schema::Type::Reader type, Schema scope) = 0;
    // Compile a schema::Type into a Type whose dependencies may safely be traversed via the schema
    // API. These dependencies may have only bootstrap schemas. Returns null if the type could not
    // be constructed due to already-reported errors.
    //
    // `scope` is the schema
  };

  NodeTranslator(Resolver& resolver, ErrorReporter& errorReporter,
                 const Declaration::Reader& decl, Orphan<schema::Node> wipNode,
                 bool compileAnnotations);
  // Construct a NodeTranslator to translate the given declaration.  The wipNode starts out with
  // `displayName`, `id`, `scopeId`, and `nestedNodes` already initialized.  The `NodeTranslator`
  // fills in the rest.

  ~NodeTranslator() noexcept(false);

  struct NodeSet {
    schema::Node::Reader node;
    // The main node.

    kj::Array<schema::Node::Reader> auxNodes;
    // Auxiliary nodes that were produced when translating this node and should be loaded along
    // with it.  In particular, structs that contain groups (or named unions) spawn extra nodes
    // representing those, and interfaces spawn struct nodes representing method params/results.
  };

  NodeSet getBootstrapNode();
  // Get an incomplete version of the node in which pointer-typed value expressions have not yet
  // been translated.  Instead, for all `schema.Value` objects representing pointer-type values,
  // the value is set to an appropriate "empty" value.  This version of the schema can be used to
  // bootstrap the dynamic API which can then in turn be used to encode the missing complex values.
  //
  // If the final node has already been built, this will actually return the final node (in fact,
  // it's the same node object).

  NodeSet finish();
  // Finish translating the node (including filling in all the pieces that are missing from the
  // bootstrap node) and return it.

  static kj::Maybe<Resolver::ResolveResult> compileDecl(
      uint64_t scopeId, uint scopeParameterCount, Resolver& resolver, ErrorReporter& errorReporter,
      Expression::Reader expression, schema::Brand::Builder brandBuilder);
  // Compile a one-off declaration expression without building a NodeTranslator. Used for
  // evaluating aliases.
  //
  // `brandBuilder` may be used to construct a message which will fill in ResolvedDecl::brand in
  // the result.

private:
  class DuplicateNameDetector;
  class DuplicateOrdinalDetector;
  class StructLayout;
  class StructTranslator;
  class BrandedDecl;
  class BrandScope;

  Resolver& resolver;
  ErrorReporter& errorReporter;
  Orphanage orphanage;
  bool compileAnnotations;
  kj::Own<BrandScope> localBrand;

  Orphan<schema::Node> wipNode;
  // The work-in-progress schema node.

  kj::Vector<Orphan<schema::Node>> groups;
  // If this is a struct node and it contains groups, these are the nodes for those groups,  which
  // must be loaded together with the top-level node.

  kj::Vector<Orphan<schema::Node>> paramStructs;
  // If this is an interface, these are the auto-generated structs representing params and results.

  struct UnfinishedValue {
    Expression::Reader source;
    schema::Type::Reader type;
    Schema typeScope;
    schema::Value::Builder target;
  };
  kj::Vector<UnfinishedValue> unfinishedValues;
  // List of values in `wipNode` which have not yet been interpreted, because they are structs
  // or lists and as such interpreting them require using the types' schemas (to take advantage
  // of the dynamic API).  Once bootstrap schemas have been built, they can be used to interpret
  // these values.

  void compileNode(Declaration::Reader decl, schema::Node::Builder builder);

  void compileConst(Declaration::Const::Reader decl, schema::Node::Const::Builder builder);
  void compileAnnotation(Declaration::Annotation::Reader decl,
                         schema::Node::Annotation::Builder builder);

  void compileEnum(Void decl, List<Declaration>::Reader members,
                   schema::Node::Builder builder);
  void compileStruct(Void decl, List<Declaration>::Reader members,
                     schema::Node::Builder builder);
  void compileInterface(Declaration::Interface::Reader decl,
                        List<Declaration>::Reader members,
                        schema::Node::Builder builder);
  // The `members` arrays contain only members with ordinal numbers, in code order.  Other members
  // are handled elsewhere.

  struct ImplicitParams {
    // Represents a set of implicit parameters visible in the current context.

    uint64_t scopeId;
    // If zero, then any reference to an implciit param in this context should be compiled to a
    // `implicitMethodParam` AnyPointer. If non-zero, it should be complied to a `parameter`
    // AnyPointer.

    List<Declaration::BrandParameter>::Reader params;
  };

  static inline ImplicitParams noImplicitParams() {
    return { 0, List<Declaration::BrandParameter>::Reader() };
  }

  template <typename InitBrandFunc>
  uint64_t compileParamList(kj::StringPtr methodName, uint16_t ordinal, bool isResults,
                            Declaration::ParamList::Reader paramList,
                            List<Declaration::BrandParameter>::Reader implicitParams,
                            InitBrandFunc&& initBrand);
  // Compile a param (or result) list and return the type ID of the struct type.

  kj::Maybe<BrandedDecl> compileDeclExpression(
      Expression::Reader source, ImplicitParams implicitMethodParams);
  // Compile an expression which is expected to resolve to a declaration or type expression.

  bool compileType(Expression::Reader source, schema::Type::Builder target,
                   ImplicitParams implicitMethodParams);
  // Returns false if there was a problem, in which case value expressions of this type should
  // not be parsed.

  void compileDefaultDefaultValue(schema::Type::Reader type, schema::Value::Builder target);
  // Initializes `target` to contain the "default default" value for `type`.

  void compileBootstrapValue(
      Expression::Reader source, schema::Type::Reader type, schema::Value::Builder target,
      Schema typeScope = Schema());
  // Calls compileValue() if this value should be interpreted at bootstrap time.  Otheriwse,
  // adds the value to `unfinishedValues` for later evaluation.
  //
  // If `type` comes from some other node, `typeScope` is the schema for that node. This is only
  // really needed for looking up generic parameter bindings, therefore if the type comes from
  // the node being built, an empty "Schema" (the default) works here because the node being built
  // is of course being built for all possible bindings and thus none of its generic parameters are
  // bound.

  void compileValue(Expression::Reader source, schema::Type::Reader type,
                    Schema typeScope, schema::Value::Builder target, bool isBootstrap);
  // Interprets the value expression and initializes `target` with the result.

  kj::Maybe<DynamicValue::Reader> readConstant(Expression::Reader name, bool isBootstrap);
  // Get the value of the given constant.  May return null if some error occurs, which will already
  // have been reported.

  Orphan<List<schema::Annotation>> compileAnnotationApplications(
      List<Declaration::AnnotationApplication>::Reader annotations,
      kj::StringPtr targetsFlagName);
};

class ValueTranslator {
public:
  class Resolver {
  public:
    virtual kj::Maybe<DynamicValue::Reader> resolveConstant(Expression::Reader name) = 0;
  };

  ValueTranslator(Resolver& resolver, ErrorReporter& errorReporter, Orphanage orphanage)
      : resolver(resolver), errorReporter(errorReporter), orphanage(orphanage) {}

  kj::Maybe<Orphan<DynamicValue>> compileValue(Expression::Reader src, Type type);

private:
  Resolver& resolver;
  ErrorReporter& errorReporter;
  Orphanage orphanage;

  Orphan<DynamicValue> compileValueInner(Expression::Reader src, Type type);
  // Helper for compileValue().

  void fillStructValue(DynamicStruct::Builder builder,
                       List<Expression::Param>::Reader assignments);
  // Interprets the given assignments and uses them to fill in the given struct builder.

  kj::String makeNodeName(Schema node);
  kj::String makeTypeName(Type type);

  kj::Maybe<ListSchema> makeListSchemaOf(schema::Type::Reader elementType);
};

}  // namespace compiler
}  // namespace capnp

#endif  // CAPNP_COMPILER_NODE_TRANSLATOR_H_