Create some type aliases for string Contexts

src/libexpr/eval-cache.cc

@@ -254,7 +254,7 @@ struct AttrDb
                 return {{rowId, attrs}};
             }
             case AttrType::String: {
-                std::vector<std::pair<Path, std::string>> context;
+                NixStringContext context;
                 if (!queryAttribute.isNull(3))
                     for (auto & s : tokenizeString<std::vector<std::string>>(queryAttribute.getStr(3), ";"))
                         context.push_back(decodeContext(s));

src/libexpr/eval-cache.hh

@@ -52,7 +52,7 @@ struct misc_t {};
 struct failed_t {};
 typedef uint64_t AttrId;
 typedef std::pair<AttrId, Symbol> AttrKey;
-typedef std::pair<std::string, std::vector<std::pair<Path, std::string>>> string_t;
+typedef std::pair<std::string, NixStringContext> string_t;
 
 typedef std::variant<
     std::vector<Symbol>,

src/libexpr/eval.cc

@@ -1903,7 +1903,7 @@ std::string_view EvalState::forceString(Value & v, const Pos & pos)
 
 /* Decode a context string ‘!<name>!<path>’ into a pair <path,
    name>. */
-std::pair<std::string, std::string> decodeContext(std::string_view s)
+NixStringContextElem decodeContext(std::string_view s)
 {
     if (s.at(0) == '!') {
         size_t index = s.find("!", 1);
@@ -1921,9 +1921,9 @@ void copyContext(const Value & v, PathSet & context)
 }
 
 
-std::vector<std::pair<Path, std::string>> Value::getContext()
+NixStringContext Value::getContext()
 {
-    std::vector<std::pair<Path, std::string>> res;
+    NixStringContext res;
     assert(internalType == tString);
     if (string.context)
         for (const char * * p = string.context; *p; ++p)

src/libexpr/eval.hh

@@ -430,7 +430,7 @@ std::string showType(const Value & v);
 
 /* Decode a context string ‘!<name>!<path>’ into a pair <path,
    name>. */
-std::pair<std::string, std::string> decodeContext(std::string_view s);
+NixStringContextElem decodeContext(std::string_view s);
 
 /* If `path' refers to a directory, then append "/default.nix". */
 Path resolveExprPath(Path path);

src/libexpr/primops/context.cc

@@ -82,7 +82,7 @@ static void prim_getContext(EvalState & state, const Pos & pos, Value * * args,
             drv = std::string(p, 1);
             path = &drv;
         } else if (p.at(0) == '!') {
-            std::pair<std::string, std::string> ctx = decodeContext(p);
+            NixStringContextElem ctx = decodeContext(p);
             drv = ctx.first;
             output = ctx.second;
             path = &drv;

src/libexpr/value.hh

@@ -64,6 +64,8 @@ class JSONPlaceholder;
 
 typedef int64_t NixInt;
 typedef double NixFloat;
+typedef std::pair<Path, std::string> NixStringContextElem;
+typedef std::vector<NixStringContextElem> NixStringContext;
 
 /* External values must descend from ExternalValueBase, so that
  * type-agnostic nix functions (e.g. showType) can be implemented
@@ -368,7 +370,7 @@ public:
        non-trivial. */
     bool isTrivial() const;
 
-    std::vector<std::pair<Path, std::string>> getContext();
+    NixStringContext getContext();
 
     auto listItems()
     {