libexpr/parser: Test experimental features

Currently, the parser relies on the global experimental feature flags.
In order to properly test conditional language features, we instead need
to pass it around in the parser::State.

This means that the parser cannot cache the result of isEnabled anymore,
which wouldn't necessarily hurt performance if the function didn't
perform a linear search on the list of enabled features on every single
call. While we could simply evaluate once at the start of parsing and
cache the result in the parser state, the more sustainable solution
would be to fix `isEnabled` such that all callers may profit from the
performance improvement.

Change-Id: Ic9b9c5d882b6270e1114988b63e6064d36c25cf2

6 files changed, 32 insertions, 11 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 120130eb3..741a24e3c 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2808,20 +2808,20 @@ Expr & EvalState::parseExprFromFile(const SourcePath & path, std::shared_ptr<Sta
 }
 
 
-Expr & EvalState::parseExprFromString(std::string s_, const SourcePath & basePath, std::shared_ptr<StaticEnv> & staticEnv)
+Expr & EvalState::parseExprFromString(std::string s_, const SourcePath & basePath, std::shared_ptr<StaticEnv> & staticEnv, const ExperimentalFeatureSettings & xpSettings)
 {
     // NOTE this method (and parseStdin) must take care to *fully copy* their input
     // into their respective Pos::Origin until the parser stops overwriting its input
     // data.
     auto s = make_ref<std::string>(s_);
     s_.append("\0\0", 2);
-    return *parse(s_.data(), s_.size(), Pos::String{.source = s}, basePath, staticEnv);
+    return *parse(s_.data(), s_.size(), Pos::String{.source = s}, basePath, staticEnv, xpSettings);
 }
 
 
-Expr & EvalState::parseExprFromString(std::string s, const SourcePath & basePath)
+Expr & EvalState::parseExprFromString(std::string s, const SourcePath & basePath, const ExperimentalFeatureSettings & xpSettings)
 {
-    return parseExprFromString(std::move(s), basePath, staticBaseEnv);
+    return parseExprFromString(std::move(s), basePath, staticBaseEnv, xpSettings);
 }
 
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index c1779de15..ff45efc08 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -344,8 +344,8 @@ public:
     /**
      * Parse a Nix expression from the specified string.
      */
-    Expr & parseExprFromString(std::string s, const SourcePath & basePath, std::shared_ptr<StaticEnv> & staticEnv);
-    Expr & parseExprFromString(std::string s, const SourcePath & basePath);
+    Expr & parseExprFromString(std::string s, const SourcePath & basePath, std::shared_ptr<StaticEnv> & staticEnv, const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
+    Expr & parseExprFromString(std::string s, const SourcePath & basePath, const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
     Expr & parseStdin();
 
@@ -568,7 +568,8 @@ private:
         size_t length,
         Pos::Origin origin,
         const SourcePath & basePath,
-        std::shared_ptr<StaticEnv> & staticEnv);
+        std::shared_ptr<StaticEnv> & staticEnv,
+        const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings);
 
     /**
      * Current Nix call stack depth, used with `max-call-depth` setting to throw stack overflow hopefully before we run out of system stack.
diff --git a/src/libexpr/parser/parser.cc b/src/libexpr/parser/parser.cc
index b7a105fe7..68aa3ddc5 100644
--- a/src/libexpr/parser/parser.cc
+++ b/src/libexpr/parser/parser.cc
@@ -631,7 +631,7 @@ template<> struct BuildAST<grammar::expr::path> : p::maybe_nothing {};
 
 template<> struct BuildAST<grammar::expr::uri> {
     static void apply(const auto & in, ExprState & s, State & ps) {
-       static bool noURLLiterals = experimentalFeatureSettings.isEnabled(Xp::NoUrlLiterals);
+       bool noURLLiterals = ps.xpSettings.isEnabled(Xp::NoUrlLiterals);
        if (noURLLiterals)
            throw ParseError({
                .msg = HintFmt("URL literals are disabled"),
@@ -832,7 +832,8 @@ Expr * EvalState::parse(
     size_t length,
     Pos::Origin origin,
     const SourcePath & basePath,
-    std::shared_ptr<StaticEnv> & staticEnv)
+    std::shared_ptr<StaticEnv> & staticEnv,
+    const ExperimentalFeatureSettings & xpSettings)
 {
     parser::State s = {
         symbols,
@@ -840,6 +841,7 @@ Expr * EvalState::parse(
         basePath,
         positions.addOrigin(origin, length),
         exprSymbols,
+        xpSettings
     };
     parser::ExprState x;
 
diff --git a/src/libexpr/parser/state.hh b/src/libexpr/parser/state.hh
index 29889152e..30803a37e 100644
--- a/src/libexpr/parser/state.hh
+++ b/src/libexpr/parser/state.hh
@@ -19,6 +19,7 @@ struct State
     SourcePath basePath;
     PosTable::Origin origin;
     const Expr::AstSymbols & s;
+    const ExperimentalFeatureSettings & xpSettings;
 
     void dupAttr(const AttrPath & attrPath, const PosIdx pos, const PosIdx prevPos);
     void dupAttr(Symbol attr, const PosIdx pos, const PosIdx prevPos);
diff --git a/tests/unit/libexpr-support/tests/libexpr.hh b/tests/unit/libexpr-support/tests/libexpr.hh
index 01dcbb34c..745aa168d 100644
--- a/tests/unit/libexpr-support/tests/libexpr.hh
+++ b/tests/unit/libexpr-support/tests/libexpr.hh
@@ -26,9 +26,9 @@ namespace nix {
                 , state({}, store)
             {
             }
-            Value eval(std::string input, bool forceValue = true) {
+            Value eval(std::string input, bool forceValue = true, const ExperimentalFeatureSettings & xpSettings = experimentalFeatureSettings) {
                 Value v;
-                Expr & e = state.parseExprFromString(input, state.rootPath(CanonPath::root));
+                Expr & e = state.parseExprFromString(input, state.rootPath(CanonPath::root), xpSettings);
                 state.eval(e, v);
                 if (forceValue)
                     state.forceValue(v, noPos);
diff --git a/tests/unit/libexpr/trivial.cc b/tests/unit/libexpr/trivial.cc
index 171727ac7..19b62aff8 100644
--- a/tests/unit/libexpr/trivial.cc
+++ b/tests/unit/libexpr/trivial.cc
@@ -59,6 +59,11 @@ namespace nix {
         ASSERT_THAT(v, IsFloatEq(1.234));
     }
 
+    TEST_F(TrivialExpressionTest, pointfloat) {
+        auto v = eval(".234");
+        ASSERT_THAT(v, IsFloatEq(0.234));
+    }
+
     TEST_F(TrivialExpressionTest, updateAttrs) {
         auto v = eval("{ a = 1; } // { b = 2; a = 3; }");
         ASSERT_THAT(v, IsAttrsOfSize(2));
@@ -81,6 +86,18 @@ namespace nix {
         ASSERT_THAT(v, IsTrue());
     }
 
+    TEST_F(TrivialExpressionTest, urlLiteral) {
+        auto v = eval("https://nixos.org");
+        ASSERT_THAT(v, IsStringEq("https://nixos.org"));
+    }
+
+    TEST_F(TrivialExpressionTest, noUrlLiteral) {
+        ExperimentalFeatureSettings mockXpSettings;
+        mockXpSettings.set("experimental-features", "no-url-literals");
+
+        ASSERT_THROW(eval("https://nixos.org", true, mockXpSettings), Error);
+    }
+
     TEST_F(TrivialExpressionTest, withFound) {
         auto v = eval("with { a = 23; }; a");
         ASSERT_THAT(v, IsIntEq(23));