Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libstore/outputs-spec.hh

@@ -0,0 +1,128 @@
+#pragma once
+///@file
+
+#include <cassert>
+#include <optional>
+#include <set>
+#include <variant>
+
+#include "json-impls.hh"
+#include "variant-wrapper.hh"
+
+namespace nix {
+
+/**
+ * An (owned) output name. Just a type alias used to make code more
+ * readible.
+ */
+typedef std::string OutputName;
+
+/**
+ * A borrowed output name. Just a type alias used to make code more
+ * readible.
+ */
+typedef std::string_view OutputNameView;
+
+struct OutputsSpec {
+    /**
+     * A non-empty set of outputs, specified by name
+     */
+    struct Names : std::set<OutputName> {
+        using std::set<OutputName>::set;
+
+        /* These need to be "inherited manually" */
+
+        Names(const std::set<OutputName> & s)
+            : std::set<OutputName>(s)
+        { assert(!empty()); }
+
+        /**
+         * Needs to be "inherited manually"
+         */
+        Names(std::set<OutputName> && s)
+            : std::set<OutputName>(s)
+        { assert(!empty()); }
+
+        /* This set should always be non-empty, so we delete this
+           constructor in order make creating empty ones by mistake harder.
+           */
+        Names() = delete;
+    };
+
+    /**
+     * The set of all outputs, without needing to name them explicitly
+     */
+    struct All : std::monostate { };
+
+    typedef std::variant<All, Names> Raw;
+
+    Raw raw;
+
+    bool operator == (const OutputsSpec &) const = default;
+    // TODO libc++ 16 (used by darwin) missing `std::set::operator <=>`, can't do yet.
+    bool operator < (const OutputsSpec & other) const {
+        return raw < other.raw;
+    }
+
+    MAKE_WRAPPER_CONSTRUCTOR(OutputsSpec);
+
+    /**
+     * Force choosing a variant
+     */
+    OutputsSpec() = delete;
+
+    bool contains(const OutputName & output) const;
+
+    /**
+     * Create a new OutputsSpec which is the union of this and that.
+     */
+    OutputsSpec union_(const OutputsSpec & that) const;
+
+    /**
+     * Whether this OutputsSpec is a subset of that.
+     */
+    bool isSubsetOf(const OutputsSpec & outputs) const;
+
+    /**
+     * Parse a string of the form 'output1,...outputN' or '*', returning
+     * the outputs spec.
+     */
+    static OutputsSpec parse(std::string_view s);
+    static std::optional<OutputsSpec> parseOpt(std::string_view s);
+
+    std::string to_string() const;
+};
+
+struct ExtendedOutputsSpec {
+    struct Default : std::monostate { };
+    using Explicit = OutputsSpec;
+
+    typedef std::variant<Default, Explicit> Raw;
+
+    Raw raw;
+
+    bool operator == (const ExtendedOutputsSpec &) const = default;
+    // TODO libc++ 16 (used by darwin) missing `std::set::operator <=>`, can't do yet.
+    bool operator < (const ExtendedOutputsSpec &) const;
+
+    MAKE_WRAPPER_CONSTRUCTOR(ExtendedOutputsSpec);
+
+    /**
+     * Force choosing a variant
+     */
+    ExtendedOutputsSpec() = delete;
+
+    /**
+     * Parse a string of the form 'prefix^output1,...outputN' or
+     * 'prefix^*', returning the prefix and the extended outputs spec.
+     */
+    static std::pair<std::string_view, ExtendedOutputsSpec> parse(std::string_view s);
+    static std::optional<std::pair<std::string_view, ExtendedOutputsSpec>> parseOpt(std::string_view s);
+
+    std::string to_string() const;
+};
+
+}
+
+JSON_IMPL(OutputsSpec)
+JSON_IMPL(ExtendedOutputsSpec)