From 62a6eeb1f3da0a5954ad2da54c454eb7fc1c6e5d Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Mon, 26 May 2014 17:02:22 +0200 Subject: [PATCH] Make the Nix search path declarative MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Nix search path lookups like are now desugared to ‘findFile nixPath ’, where ‘findFile’ is a new primop. Thus you can override the search path simply by saying let nixPath = [ { prefix = "nixpkgs"; path = "/my-nixpkgs"; } ]; in ... ... In conjunction with ‘scopedImport’ (commit c273c15cb13bb86420dda1e5341a4e19517532b5), the Nix search path can be propagated across imports, e.g. let overrides = { nixPath = [ ... ] ++ builtins.nixPath; import = fn: scopedImport overrides fn; scopedImport = attrs: fn: scopedImport (overrides // attrs) fn; builtins = builtins // overrides; }; in scopedImport overrides ./nixos --- src/libexpr/common-opts.cc | 4 +--- src/libexpr/eval.hh | 5 ++++- src/libexpr/nixexpr.hh | 1 + src/libexpr/parser.y | 23 ++++++++++---------- src/libexpr/primops.cc | 32 ++++++++++++++++++++++++++++ tests/lang/eval-okay-search-path.exp | 2 +- tests/lang/eval-okay-search-path.nix | 1 + 7 files changed, 51 insertions(+), 17 deletions(-) diff --git a/src/libexpr/common-opts.cc b/src/libexpr/common-opts.cc index 14a75f7b6f..a3ea202e88 100644 --- a/src/libexpr/common-opts.cc +++ b/src/libexpr/common-opts.cc @@ -48,9 +48,7 @@ Path lookupFileArg(EvalState & state, string s) { if (s.size() > 2 && s.at(0) == '<' && s.at(s.size() - 1) == '>') { Path p = s.substr(1, s.size() - 2); - Path p2 = state.findFile(p); - if (p2 == "") throw Error(format("file `%1%' was not found in the Nix search path (add it using $NIX_PATH or -I)") % p); - return p2; + return state.findFile(p); } else return absPath(s); } diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh index 200ec75e0f..aa706cf983 100644 --- a/src/libexpr/eval.hh +++ b/src/libexpr/eval.hh @@ -86,6 +86,9 @@ typedef std::map SrcToStore; std::ostream & operator << (std::ostream & str, const Value & v); +typedef list > SearchPath; + + class EvalState { public: @@ -111,7 +114,6 @@ private: #endif FileEvalCache fileEvalCache; - typedef list > SearchPath; SearchPath searchPath; public: @@ -137,6 +139,7 @@ public: /* Look up a file in the search path. */ Path findFile(const string & path); + Path findFile(SearchPath & searchPath, const string & path); /* Evaluate an expression to normal form, storing the result in value `v'. */ diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh index fbd5bad81e..8826ad2323 100644 --- a/src/libexpr/nixexpr.hh +++ b/src/libexpr/nixexpr.hh @@ -142,6 +142,7 @@ struct ExprVar : Expr unsigned int level; unsigned int displ; + ExprVar(const Symbol & name) : name(name) { }; ExprVar(const Pos & pos, const Symbol & name) : pos(pos), name(name) { }; COMMON_METHODS Value * maybeThunk(EvalState & state, Env & env); diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y index 698e8ce3ff..134d68d6e1 100644 --- a/src/libexpr/parser.y +++ b/src/libexpr/parser.y @@ -386,17 +386,10 @@ expr_simple | PATH { $$ = new ExprPath(absPath($1, data->basePath)); } | SPATH { string path($1 + 1, strlen($1) - 2); - Path path2 = data->state.findFile(path); - /* The file wasn't found in the search path. However, we can't - throw an error here, because the expression might never be - evaluated. So return an expression that lazily calls - ‘throw’. */ - $$ = path2 == "" - ? (Expr * ) new ExprApp( - new ExprBuiltin(data->symbols.create("throw")), - new ExprString(data->symbols.create( - (format("file `%1%' was not found in the Nix search path (add it using $NIX_PATH or -I)") % path).str()))) - : (Expr * ) new ExprPath(path2); + $$ = new ExprApp(CUR_POS, + new ExprApp(new ExprVar(data->symbols.create("__findFile")), + new ExprVar(data->symbols.create("nixPath"))), + new ExprString(data->symbols.create(path))); } | URI { $$ = new ExprString(data->symbols.create($1)); } | '(' expr ')' { $$ = $2; } @@ -636,6 +629,12 @@ void EvalState::addToSearchPath(const string & s, bool warn) Path EvalState::findFile(const string & path) +{ + return findFile(searchPath, path); +} + + +Path EvalState::findFile(SearchPath & searchPath, const string & path) { foreach (SearchPath::iterator, i, searchPath) { Path res; @@ -650,7 +649,7 @@ Path EvalState::findFile(const string & path) } if (pathExists(res)) return canonPath(res); } - return ""; + throw ThrownError(format("file `%1%' was not found in the Nix search path (add it using $NIX_PATH or -I)") % path); } diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc index e492ff683a..333748973d 100644 --- a/src/libexpr/primops.cc +++ b/src/libexpr/primops.cc @@ -654,6 +654,37 @@ static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Va } +/* Find a file in the Nix search path. Used to implement paths, + which are desugared to ‘findFile nixPath "x"’. */ +static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Value & v) +{ + state.forceList(*args[0], pos); + + SearchPath searchPath; + + for (unsigned int n = 0; n < args[0]->list.length; ++n) { + Value & v2(*args[0]->list.elems[n]); + state.forceAttrs(v2, pos); + + string prefix; + Bindings::iterator i = v2.attrs->find(state.symbols.create("prefix")); + if (i != v2.attrs->end()) + prefix = state.forceStringNoCtx(*i->value, pos); + + i = v2.attrs->find(state.symbols.create("path")); + if (i == v2.attrs->end()) + throw EvalError(format("attribute `path' missing, at %1%") % pos); + PathSet context; + string path = state.coerceToPath(pos, *i->value, context); + + searchPath.push_back(std::pair(prefix, path)); + } + + string path = state.forceStringNoCtx(*args[1], pos); + mkPath(v, state.findFile(searchPath, path).c_str()); +} + + /************************************************************* * Creating files *************************************************************/ @@ -1293,6 +1324,7 @@ void EvalState::createBaseEnv() addPrimOp("baseNameOf", 1, prim_baseNameOf); addPrimOp("dirOf", 1, prim_dirOf); addPrimOp("__readFile", 1, prim_readFile); + addPrimOp("__findFile", 2, prim_findFile); // Creating files addPrimOp("__toXML", 1, prim_toXML); diff --git a/tests/lang/eval-okay-search-path.exp b/tests/lang/eval-okay-search-path.exp index d0bc8c5e86..ad05904ba1 100644 --- a/tests/lang/eval-okay-search-path.exp +++ b/tests/lang/eval-okay-search-path.exp @@ -1 +1 @@ -"abcc" +"abcca" diff --git a/tests/lang/eval-okay-search-path.nix b/tests/lang/eval-okay-search-path.nix index 501d5f3f48..e0f433fec6 100644 --- a/tests/lang/eval-okay-search-path.nix +++ b/tests/lang/eval-okay-search-path.nix @@ -8,3 +8,4 @@ assert length (filter (x: x.prefix == "nix") nixPath) == 1; assert length (filter (x: baseNameOf x.path == "dir4") nixPath) == 1; import + import + import + import + + (let nixPath = [ { path = ./dir1; } { path = ./dir2; } ]; in import )