From 7a02865b94f107de1c1ef797b89d45ecd3f01cf1 Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Tue, 25 Aug 2020 14:06:01 +0200 Subject: [PATCH] Move import docs --- doc/manual/src/expressions/builtins-prefix.md | 53 ----------- src/libexpr/primops.cc | 93 ++++++++++++++++--- tests/function-trace.sh | 12 --- 3 files changed, 80 insertions(+), 78 deletions(-) diff --git a/doc/manual/src/expressions/builtins-prefix.md b/doc/manual/src/expressions/builtins-prefix.md index ae3bb150c..0f7c3d32f 100644 --- a/doc/manual/src/expressions/builtins-prefix.md +++ b/doc/manual/src/expressions/builtins-prefix.md @@ -13,56 +13,3 @@ For instance, `derivation` is also available as `builtins.derivation`. `derivation` is described in [its own section](derivations.md). - - `import` *path*; `builtins.import` *path* - - Load, parse and return the Nix expression in the file *path*. If - *path* is a directory, the file ` default.nix ` in that directory - is loaded. Evaluation aborts if the file doesn’t exist or contains - an incorrect Nix expression. `import` implements Nix’s module - system: you can put any Nix expression (such as a set or a - function) in a separate file, and use it from Nix expressions in - other files. - - > **Note** - > - > Unlike some languages, `import` is a regular function in Nix. - > Paths using the angle bracket syntax (e.g., `import` *\*) - > are [normal path values](language-values.md). - - A Nix expression loaded by `import` must not contain any *free - variables* (identifiers that are not defined in the Nix expression - itself and are not built-in). Therefore, it cannot refer to - variables that are in scope at the call site. For instance, if you - have a calling expression - - ```nix - rec { - x = 123; - y = import ./foo.nix; - } - ``` - - then the following `foo.nix` will give an error: - - ```nix - x + 456 - ``` - - since `x` is not in scope in `foo.nix`. If you want `x` to be - available in `foo.nix`, you should pass it as a function argument: - - ```nix - rec { - x = 123; - y = import ./foo.nix x; - } - ``` - - and - - ```nix - x: x + 456 - ``` - - (The function argument doesn’t have to be called `x` in `foo.nix`; - any name would work.) diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc index 2d3433200..821cf0782 100644 --- a/src/libexpr/primops.cc +++ b/src/libexpr/primops.cc @@ -74,10 +74,10 @@ void EvalState::realiseContext(const PathSet & context) /* Load and evaluate an expression from path specified by the argument. */ -static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args, Value & v) +static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vScope, Value & v) { PathSet context; - Path path = state.coerceToPath(pos, *args[1], context); + Path path = state.coerceToPath(pos, vPath, context); try { state.realiseContext(context); @@ -99,6 +99,7 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args return std::nullopt; return storePath; }; + if (auto optStorePath = isValidDerivationInStore()) { auto storePath = *optStorePath; Derivation drv = readDerivation(*state.store, realPath, Derivation::nameFromPath(storePath)); @@ -133,17 +134,18 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args mkApp(v, **fun, w); state.forceAttrs(v, pos); } else { - state.forceAttrs(*args[0]); - if (args[0]->attrs->empty()) + if (!vScope) state.evalFile(realPath, v); else { - Env * env = &state.allocEnv(args[0]->attrs->size()); + state.forceAttrs(*vScope); + + Env * env = &state.allocEnv(vScope->attrs->size()); env->up = &state.baseEnv; StaticEnv staticEnv(false, &state.staticBaseEnv); unsigned int displ = 0; - for (auto & attr : *args[0]->attrs) { + for (auto & attr : *vScope->attrs) { staticEnv.vars[attr.name] = displ; env->values[displ++] = attr.value; } @@ -156,6 +158,77 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args } } +static RegisterPrimOp primop_scopedImport(RegisterPrimOp::Info { + .name = "scopedImport", + .arity = 2, + .fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v) + { + import(state, pos, *args[1], args[0], v); + } +}); + +static RegisterPrimOp primop_import({ + .name = "import", + .args = {"path"}, + .doc = R"( + Load, parse and return the Nix expression in the file *path*. If + *path* is a directory, the file ` default.nix ` in that directory + is loaded. Evaluation aborts if the file doesn’t exist or contains + an incorrect Nix expression. `import` implements Nix’s module + system: you can put any Nix expression (such as a set or a + function) in a separate file, and use it from Nix expressions in + other files. + + > **Note** + > + > Unlike some languages, `import` is a regular function in Nix. + > Paths using the angle bracket syntax (e.g., `import` *\*) + > are [normal path values](language-values.md). + + A Nix expression loaded by `import` must not contain any *free + variables* (identifiers that are not defined in the Nix expression + itself and are not built-in). Therefore, it cannot refer to + variables that are in scope at the call site. For instance, if you + have a calling expression + + ```nix + rec { + x = 123; + y = import ./foo.nix; + } + ``` + + then the following `foo.nix` will give an error: + + ```nix + x + 456 + ``` + + since `x` is not in scope in `foo.nix`. If you want `x` to be + available in `foo.nix`, you should pass it as a function argument: + + ```nix + rec { + x = 123; + y = import ./foo.nix x; + } + ``` + + and + + ```nix + x: x + 456 + ``` + + (The function argument doesn’t have to be called `x` in `foo.nix`; + any name would work.) + )", + .fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v) + { + import(state, pos, *args[0], nullptr, v); + } +}); + /* Want reasonable symbol names, so extern C */ /* !!! Should we pass the Pos or the file name too? */ extern "C" typedef void (*ValueInitializer)(EvalState & state, Value & v); @@ -3429,12 +3502,6 @@ void EvalState::createBaseEnv() addConstant("__langVersion", v); // Miscellaneous - auto vScopedImport = addPrimOp("scopedImport", 2, prim_scopedImport); - Value * v2 = allocValue(); - mkAttrs(*v2, 0); - mkApp(v, *vScopedImport, *v2); - forceValue(v); - addConstant("import", v); if (evalSettings.enableNativeCode) { addPrimOp("__importNative", 2, prim_importNative); addPrimOp("__exec", 1, prim_exec); @@ -3444,7 +3511,7 @@ void EvalState::createBaseEnv() mkList(v, searchPath.size()); int n = 0; for (auto & i : searchPath) { - v2 = v.listElems()[n++] = allocValue(); + auto v2 = v.listElems()[n++] = allocValue(); mkAttrs(*v2, 2); mkString(*allocAttr(*v2, symbols.create("path")), i.second); mkString(*allocAttr(*v2, symbols.create("prefix")), i.first); diff --git a/tests/function-trace.sh b/tests/function-trace.sh index 182a4d5c2..3b7f364e3 100755 --- a/tests/function-trace.sh +++ b/tests/function-trace.sh @@ -32,8 +32,6 @@ expect_trace() { # failure inside a tryEval expect_trace 'builtins.tryEval (throw "example")' " -function-trace entered undefined position at -function-trace exited undefined position at function-trace entered (string):1:1 at function-trace entered (string):1:19 at function-trace exited (string):1:19 at @@ -42,32 +40,24 @@ function-trace exited (string):1:1 at # Missing argument to a formal function expect_trace '({ x }: x) { }' " -function-trace entered undefined position at -function-trace exited undefined position at function-trace entered (string):1:1 at function-trace exited (string):1:1 at " # Too many arguments to a formal function expect_trace '({ x }: x) { x = "x"; y = "y"; }' " -function-trace entered undefined position at -function-trace exited undefined position at function-trace entered (string):1:1 at function-trace exited (string):1:1 at " # Not enough arguments to a lambda expect_trace '(x: y: x + y) 1' " -function-trace entered undefined position at -function-trace exited undefined position at function-trace entered (string):1:1 at function-trace exited (string):1:1 at " # Too many arguments to a lambda expect_trace '(x: x) 1 2' " -function-trace entered undefined position at -function-trace exited undefined position at function-trace entered (string):1:1 at function-trace exited (string):1:1 at function-trace entered (string):1:1 at @@ -76,8 +66,6 @@ function-trace exited (string):1:1 at # Not a function expect_trace '1 2' " -function-trace entered undefined position at -function-trace exited undefined position at function-trace entered (string):1:1 at function-trace exited (string):1:1 at "