[vcpkg] Further JSON error improvements (microsoft#13399)

* [vcpkg] Split vcpkg/base/json.h into vcpkg/base/jsonreader.h

* [vcpkg] Extract definitions of Configuration-Deserializer (& friends)

These types are only used by VcpkgPaths during the initial parse.

* [vcpkg] Introduce levenshtein-distance suggestions for json errors

* [vcpkg] Fix regression in supports handling

* [vcpkg] Fix signed/unsigned mismatch

* [vcpkg] Address CR comments

* [vcpkg] Address CR comments

* Fix compiler error from merge conflict.

* [vcpkg] Change parameters of Reader::check_for_unexpected_fields to better match declaration

* [vcpkg] Improve errors from features set

* [vcpkg] Fix includes

* [vcpkg] Reuse code

* [vcpkg] Check the "name" field always to maximize error information

* [docs] Improve english phrasing in manifests.md

* [vcpkg] Correct docs link for manifests

Co-authored-by: Robert Schumacher <[email protected]>
Co-authored-by: Billy Robert O'Neal III <[email protected]>

docs/users/manifests.md

@@ -28,20 +28,21 @@ In this document, we have basic information on [Writing a Manifest](#writing-a-m
 the [vcpkg Command Line Interface](#command-line-interface),
 and a little more information on [CMake](#cmake-integration) integration.
 
-Check out the [manifest cmake example](../examples/manifest-mode-cmake.md) for an example project using CMake and manifest mode.
+Check out the [manifest cmake example](../examples/manifest-mode-cmake.md) for an example project using CMake and
+manifest mode.
 
 ## Writing a Manifest
 
-A manifest is a JSON-formatted file which lies at the root of your project.
+A manifest is a JSON-formatted file named `vcpkg.json` which lies at the root of your project.
 It contains all the information a person needs to know to get dependencies for your project,
 as well as all the metadata about your project that a person who depends on you might be interested in.
 
-Every manifest is named `vcpkg.json`, and has a top level object. It is a strict JSON file,
-and can't contain things like comments or trailing commas - however,
-you can use field names that start with `$` to write your comments.
+Manifests follow strict JSON: they can't contain C++-style comments (`//`) nor trailing commas. However
+you can use field names that start with `$` to write your comments in any object that has a well-defined set of keys.
+These comment fields are not allowed in any objects which permit user-defined keys (such as `"features"`).
 
-All of the fields that `vcpkg.json` supports are as follows; the most important ones are [`"name"`](#name),
-the [version fields](#version-fields), and [`"dependencies"`](#dependencies):
+Each manifest contains a top level object with the fields documented below; the most important ones are
+[`"name"`](#name), the [version fields](#version-fields), and [`"dependencies"`](#dependencies):
 
 ### `"name"`
 

toolsrc/include/vcpkg/base/fwd/json.h

@@ -1,44 +1,10 @@
 #pragma once
 
-#include <vcpkg/base/fwd/optional.h>
-#include <vcpkg/base/fwd/span.h>
-#include <vcpkg/base/fwd/stringview.h>
-
 namespace vcpkg::Json
 {
     struct JsonStyle;
     enum class ValueKind : int;
     struct Value;
     struct Object;
     struct Array;
-
-    struct ReaderError;
-    struct BasicReaderError;
-    struct Reader;
-
-    // This is written all the way out so that one can include a subclass in a header
-    template<class Type>
-    struct IDeserializer
-    {
-        using type = Type;
-        virtual StringView type_name() const = 0;
-
-        virtual Span<const StringView> valid_fields() const;
-
-        virtual Optional<Type> visit_null(Reader&);
-        virtual Optional<Type> visit_boolean(Reader&, bool);
-        virtual Optional<Type> visit_integer(Reader& r, int64_t i);
-        virtual Optional<Type> visit_number(Reader&, double);
-        virtual Optional<Type> visit_string(Reader&, StringView);
-        virtual Optional<Type> visit_array(Reader&, const Array&);
-        virtual Optional<Type> visit_object(Reader&, const Object&);
-
-    protected:
-        IDeserializer() = default;
-        IDeserializer(const IDeserializer&) = default;
-        IDeserializer& operator=(const IDeserializer&) = default;
-        IDeserializer(IDeserializer&&) = default;
-        IDeserializer& operator=(IDeserializer&&) = default;
-        virtual ~IDeserializer() = default;
-    };
 }

toolsrc/include/vcpkg/base/fwd/span.h

@@ -4,4 +4,7 @@ namespace vcpkg
 {
     template<class T>
     struct Span;
+
+    template<class T>
+    using View = Span<const T>;
 }