refactor(Error): error propagation uses Expected

Author: alandefreitas

include/mrdocs/Generator.hpp

@@ -102,7 +102,7 @@ class MRDOCS_VISIBLE
     */
     MRDOCS_DECL
     virtual
-    Error
+    Expected<void>
     build(
         std::string_view outputPath,
         Corpus const& corpus) const;
@@ -120,7 +120,7 @@ class MRDOCS_VISIBLE
         the object before returning.
     */
     MRDOCS_DECL
-    Error
+    Expected<void>
     build(Corpus const& corpus) const;
 
     /** Build reference documentation for the corpus.
@@ -141,7 +141,7 @@ class MRDOCS_VISIBLE
     */
     MRDOCS_DECL
     virtual
-    Error
+    Expected<void>
     buildOne(
         std::ostream& os,
         Corpus const& corpus) const = 0;
@@ -160,7 +160,7 @@ class MRDOCS_VISIBLE
         @param corpus The metadata to emit.
     */
     MRDOCS_DECL
-    Error
+    Expected<void>
     buildOne(
         std::string_view fileName,
         Corpus const& corpus) const;
@@ -176,7 +176,7 @@ class MRDOCS_VISIBLE
         @param corpus The metadata to emit.
     */
     MRDOCS_DECL
-    Error
+    Expected<void>
     buildOneString(
         std::string& dest,
         Corpus const& corpus) const;

include/mrdocs/Support/Error.hpp

@@ -77,7 +77,7 @@ class MRDOCS_DECL
         A default constructed error is
         equivalent to success.
     */
-    Error() noexcept = default;
+    Error() noexcept = delete;
 
     /** Constructor.
     */
@@ -209,24 +209,6 @@ class MRDOCS_DECL
     */
     [[noreturn]] void Throw() &&;
 
-    /** Throw Exception(*this), or do nothing if no failure.
-    */
-    void maybeThrow() const&
-    {
-        if(! failed())
-            return;
-        Throw();
-    }
-
-    /** Throw Exception(std::move(*this)), or do nothing if no failure.
-    */
-    void maybeThrow() &&
-    {
-        if(! failed())
-            return;
-        Throw();
-    }
-
     constexpr
     void
     swap(Error& rhs) noexcept
@@ -244,10 +226,6 @@ class MRDOCS_DECL
     {
         lhs.swap(rhs);
     }
-
-    /** Return a value indicating success.
-    */
-    static Error success() noexcept;
 };
 
 //------------------------------------------------
@@ -1934,36 +1912,6 @@ class Expected<T, E>
         : unex_(std::move(u).error()), has_value_(false)
     { }
 
-// The following constructors are extensions that allow
-// Expected to be constructed directly from an error type
-// if this is not ambiguous with the value type. This
-// is not part of std::expected. MRDOCS_EXPECTED_FROM_ERROR
-// can be defined to disable this behavior.
-#ifndef MRDOCS_EXPECTED_FROM_ERROR
-    template <class G = E>
-    requires
-        std::is_constructible_v<E, const G&> &&
-        (!std::is_constructible_v<T, const G&>)
-    constexpr
-    explicit(!std::is_convertible_v<const G&, E>)
-    Expected(const G& u)
-    noexcept(std::is_nothrow_constructible_v<E, const G&>)
-        : unex_(u)
-        , has_value_(false)
-    { }
-
-    template <class G = E>
-    requires
-        std::is_constructible_v<E, G> &&
-        (!std::is_constructible_v<T, G>)
-    constexpr
-    explicit(!std::is_convertible_v<G, E>)
-    Expected(G&& u)
-    noexcept(std::is_nothrow_constructible_v<E, G>)
-        : unex_(std::move(u)), has_value_(false)
-    { }
-#endif
-
     constexpr explicit
     Expected(std::in_place_t) noexcept
         : Expected()
@@ -2677,14 +2625,6 @@ struct FormatString
     source_location loc;
 };
 
-inline
-Error
-Error::
-success() noexcept
-{
-    return Error();
-}
-
 /** Return a formatted error.
 
     @param fs The format string. This

include/mrdocs/Support/Path.hpp

@@ -24,8 +24,12 @@ namespace mrdocs {
 struct MRDOCS_VISIBLE
     AnyFileVisitor
 {
-    virtual ~AnyFileVisitor() = 0;
-    virtual Error visitFile(std::string_view fileName) = 0;
+    virtual
+    ~AnyFileVisitor() = 0;
+
+    virtual
+    Expected<void>
+    visitFile(std::string_view fileName) = 0;
 };
 
 /** Call a function for each file in a directory.
@@ -38,71 +42,37 @@ struct MRDOCS_VISIBLE
     also visited, recursively.
 */
 MRDOCS_DECL
-Error
+Expected<void>
 forEachFile(
     std::string_view dirPath,
     bool recursive,
     AnyFileVisitor& visitor);
 
 namespace detail {
 template <class Visitor>
-struct FileVisitor : AnyFileVisitor
+class FileVisitor : public AnyFileVisitor
 {
+    using R = std::invoke_result_t<Visitor, std::string_view>;
+
+public:
     Visitor& visitor_;
 
     explicit FileVisitor(Visitor& v)
         : visitor_(v)
     {
     }
 
-    Error
+    Expected<void>
     visitFile(std::string_view fileName) override
     {
-        using R = std::invoke_result_t<Visitor, std::string_view>;
         if (std::same_as<R, void>)
         {
             visitor_(fileName);
-            return Error::success();
-        }
-        else
-        {
-            return toError(visitor_(fileName));
-        }
-    }
-
-    static
-    Error
-    toError(Expected<void, Error> const& e)
-    {
-        return e ? Error::success() : e.error();
-    }
-
-    template <class T>
-    static
-    Error
-    toError(Expected<T, Error> const& e)
-    {
-        return e ? toError(e.value()) : e.error();
-    }
-
-    template <class T>
-    static
-    Error
-    toError(T const& e)
-    {
-        if constexpr (std::same_as<T, Error>)
-        {
-            return e;
-        }
-        else if constexpr (std::convertible_to<T, bool>)
-        {
-            if (e)
-                return Error::success();
-            return Error("visitor returned falsy");
+            return {};
         }
         else
         {
-            return Error::success();
+            return visitor_(fileName);
         }
     }
 };
@@ -111,7 +81,7 @@ struct FileVisitor : AnyFileVisitor
 /** Visit each file in a directory.
 */
 template<class Visitor>
-Error
+Expected<void>
 forEachFile(
     std::string_view dirPath,
     bool recursive,
@@ -154,7 +124,7 @@ isAbsolute(
 /** Return an error if pathName is not absolute.
 */
 MRDOCS_DECL
-Error
+Expected<void>
 requireAbsolute(
     std::string_view pathName);
 
@@ -320,7 +290,7 @@ appendPath(
 /** Return an error if the path is not a directory.
 */
 MRDOCS_DECL
-Error
+Expected<void>
 requireDirectory(
     std::string_view pathName);
 
@@ -354,7 +324,7 @@ getSourceFilename(
     to create.
 */
 MRDOCS_DECL
-Error
+Expected<void>
 createDirectory(
     std::string_view pathName);
 

src/lib/Gen/hbs/Builder.cpp

@@ -38,18 +38,18 @@ loadPartials(
     {
         return;
     }
-    forEachFile(partialsPath, true,
-        [&](std::string_view pathName) -> Error
+    auto exp = forEachFile(partialsPath, true,
+        [&](std::string_view pathName) -> Expected<void>
         {
             // Skip directories
-            MRDOCS_CHECK_OR(!files::isDirectory(pathName), Error::success());
+            MRDOCS_CHECK_OR(!files::isDirectory(pathName), {});
 
             // Get template relative path
             std::filesystem::path relPath = pathName;
             relPath = relPath.lexically_relative(partialsPath);
 
             // Skip non-handlebars files
-            MRDOCS_CHECK_OR(relPath.extension() == ".hbs", Error::success());
+            MRDOCS_CHECK_OR(relPath.extension() == ".hbs", {});
 
             // Remove any file extensions
             while(relPath.has_extension())
@@ -58,13 +58,16 @@ loadPartials(
             }
 
             // Load partial contents
-            auto text = files::getFileText(pathName);
-            MRDOCS_CHECK_OR(text, text.error());
+            MRDOCS_TRY(std::string text, files::getFileText(pathName));
 
             // Register partial
-            hbs.registerPartial(relPath.generic_string(), *text);
-            return Error::success();
-        }).maybeThrow();
+            hbs.registerPartial(relPath.generic_string(), text);
+            return {};
+        });
+    if (!exp)
+    {
+        exp.error().Throw();
+    }
 }
 }
 
@@ -81,7 +84,7 @@ Builder(
 
     // Load JavaScript helpers
     std::string helpersPath = templatesDir("helpers");
-    forEachFile(helpersPath, true,
+    auto exp = forEachFile(helpersPath, true,
         [&](std::string_view pathName)-> Expected<void>
         {
             // Register JS helper function in the global object
@@ -92,7 +95,11 @@ Builder(
             MRDOCS_TRY(auto script, files::getFileText(pathName));
             MRDOCS_TRY(js::registerHelper(hbs_, name, ctx_, script));
             return {};
-        }).maybeThrow();
+        });
+    if (!exp)
+    {
+        exp.error().Throw();
+    }
 
     hbs_.registerHelper("primary_location",
         dom::makeInvocable([](dom::Value const& v) ->
@@ -260,19 +267,17 @@ operator()(OverloadSet const& OS)
 
 Expected<void>
 Builder::
-renderWrapped(std::ostream& os, std::function<Error()> contentsCb)
+renderWrapped(
+    std::ostream& os,
+    std::function<Expected<void>()> contentsCb)
 {
     auto const wrapperFile = fmt::format(
         "wrapper.{}.hbs", domCorpus.fileExtension);
     dom::Object ctx;
     ctx.set("contents", dom::makeInvocable([&](
         dom::Value const& options) -> Expected<dom::Value>
     {
-        Error e = contentsCb();
-        if (e.failed())
-        {
-            return Unexpected(e);
-        }
+        MRDOCS_TRY(contentsCb());
         return {};
     }));
 

src/lib/Gen/hbs/Builder.hpp

@@ -73,7 +73,9 @@ class Builder
 
      */
     Expected<void>
-    renderWrapped(std::ostream& os, std::function<Error()> contentsCb);
+    renderWrapped(
+        std::ostream& os,
+        std::function<Expected<void>()> contentsCb);
 
 private:
     /** The directory with the all templates.