Lazy trees

doc/manual/generate-manpage.nix

@@ -1,7 +1,7 @@
 { toplevel }:
 
 with builtins;
-with import ./utils.nix;
+with import <nix/utils.nix>;
 
 let
 

doc/manual/local.mk

@@ -24,7 +24,7 @@ dummy-env = env -i \
 	NIX_STATE_DIR=/dummy \
 	NIX_CONFIG='cores = 0'
 
-nix-eval = $(dummy-env) $(bindir)/nix eval --experimental-features nix-command -I nix/corepkgs=corepkgs --store dummy:// --impure --raw
+nix-eval = $(dummy-env) $(bindir)/nix eval --experimental-features nix-command -I nix=doc/manual --store dummy:// --impure --raw
 
 $(d)/%.1: $(d)/src/command-ref/%.md
 	@printf "Title: %s\n\n" "$$(basename $@ .1)" > $^.tmp

flake.nix

@@ -122,6 +122,7 @@
             bzip2 xz brotli editline
             openssl sqlite
             libarchive
+            libgit2
             boost
             lowdown-nix
             gtest

src/libcmd/common-eval-args.cc

@@ -8,6 +8,8 @@
 #include "flake/flakeref.hh"
 #include "store-api.hh"
 #include "command.hh"
+#include "fs-input-accessor.hh"
+#include "tarball.hh"
 
 namespace nix {
 
@@ -149,27 +151,29 @@ Bindings * MixEvalArgs::getAutoArgs(EvalState & state)
     for (auto & i : autoArgs) {
         auto v = state.allocValue();
         if (i.second[0] == 'E')
-            state.mkThunk_(*v, state.parseExprFromString(i.second.substr(1), absPath(".")));
+            state.mkThunk_(*v, state.parseExprFromString(i.second.substr(1), state.rootPath(absPath("."))));
         else
             v->mkString(((std::string_view) i.second).substr(1));
         res.insert(state.symbols.create(i.first), v);
     }
     return res.finish();
 }
 
-Path lookupFileArg(EvalState & state, std::string_view s)
+SourcePath lookupFileArg(EvalState & state, std::string_view s)
 {
     if (EvalSettings::isPseudoUrl(s)) {
         auto storePath = fetchers::downloadTarball(
-            state.store, EvalSettings::resolvePseudoUrl(s), "source", false).first.storePath;
-        return state.store->toRealPath(storePath);
+            state.store, EvalSettings::resolvePseudoUrl(s), "source", false).first;
+        auto accessor = makeStorePathAccessor(state.store, storePath);
+        state.registerAccessor(accessor);
+        return accessor->root();
     }
 
     else if (hasPrefix(s, "flake:")) {
         settings.requireExperimentalFeature(Xp::Flakes);
         auto flakeRef = parseFlakeRef(std::string(s.substr(6)), {}, true, false);
-        auto storePath = flakeRef.resolve(state.store).fetchTree(state.store).first.storePath;
-        return state.store->toRealPath(storePath);
+        auto [accessor, _] = flakeRef.resolve(state.store).lazyFetch(state.store);
+        return accessor->root();
     }
 
     else if (s.size() > 2 && s.at(0) == '<' && s.at(s.size() - 1) == '>') {
@@ -178,7 +182,7 @@ Path lookupFileArg(EvalState & state, std::string_view s)
     }
 
     else
-        return absPath(std::string(s));
+        return state.rootPath(absPath(std::string(s)));
 }
 
 }

src/libcmd/common-eval-args.hh

@@ -7,6 +7,7 @@ namespace nix {
 class Store;
 class EvalState;
 class Bindings;
+struct SourcePath;
 
 struct MixEvalArgs : virtual Args
 {
@@ -24,6 +25,6 @@ private:
     std::map<std::string, std::string> autoArgs;
 };
 
-Path lookupFileArg(EvalState & state, std::string_view s);
+SourcePath lookupFileArg(EvalState & state, std::string_view s);
 
 }

src/libcmd/editor-for.cc

@@ -3,8 +3,11 @@
 
 namespace nix {
 
-Strings editorFor(const Path & file, uint32_t line)
+Strings editorFor(const SourcePath & file, uint32_t line)
 {
+    auto path = file.getPhysicalPath();
+    if (!path)
+        throw Error("cannot open '%s' in an editor because it has no physical path", file);
     auto editor = getEnv("EDITOR").value_or("cat");
     auto args = tokenizeString<Strings>(editor);
     if (line > 0 && (
@@ -13,7 +16,7 @@ Strings editorFor(const Path & file, uint32_t line)
         editor.find("vim") != std::string::npos ||
         editor.find("kak") != std::string::npos))
         args.push_back(fmt("+%d", line));
-    args.push_back(file);
+    args.push_back(path->abs());
     return args;
 }
 

src/libcmd/editor-for.hh

@@ -1,11 +1,12 @@
 #pragma once
 
 #include "types.hh"
+#include "input-accessor.hh"
 
 namespace nix {
 
 /* Helper function to generate args that invoke $EDITOR on
    filename:lineno. */
-Strings editorFor(const Path & file, uint32_t line);
+Strings editorFor(const SourcePath & file, uint32_t line);
 
 }

src/libcmd/installable-flake.cc

@@ -96,8 +96,7 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
         auto v = attr->forceValue();
 
         if (v.type() == nPath) {
-            PathSet context;
-            auto storePath = state->copyPathToStore(context, Path(v.path));
+            auto storePath = v.path().fetchToStore(state->store);
             return {{
                 .path = DerivedPath::Opaque {
                     .path = std::move(storePath),

src/libcmd/installables.cc

@@ -211,9 +211,10 @@ void SourceExprCommand::completeInstallable(std::string_view prefix)
 
             evalSettings.pureEval = false;
             auto state = getEvalState();
-            Expr *e = state->parseExprFromFile(
-                resolveExprPath(state->checkSourcePath(lookupFileArg(*state, *file)))
-                );
+            auto e =
+                state->parseExprFromFile(
+                    resolveExprPath(
+                        lookupFileArg(*state, *file)));
 
             Value root;
             state->eval(e, root);
@@ -397,10 +398,10 @@ ref<eval_cache::EvalCache> openEvalCache(
     EvalState & state,
     std::shared_ptr<flake::LockedFlake> lockedFlake)
 {
-    auto fingerprint = lockedFlake->getFingerprint();
+    auto fingerprint = lockedFlake->getFingerprint(state.store);
     return make_ref<nix::eval_cache::EvalCache>(
         evalSettings.useEvalCache && evalSettings.pureEval
-            ? std::optional { std::cref(fingerprint) }
+            ? fingerprint
             : std::nullopt,
         state,
         [&state, lockedFlake]()
@@ -444,7 +445,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         else if (file)
             state->evalFile(lookupFileArg(*state, *file), *vFile);
         else {
-            auto e = state->parseExprFromString(*expr, absPath("."));
+            auto e = state->parseExprFromString(*expr, state->rootPath(absPath(".")));
             state->eval(e, *vFile);
         }
 

src/libcmd/repl.cc

@@ -590,14 +590,14 @@ bool NixRepl::processLine(std::string line)
         Value v;
         evalString(arg, v);
 
-        const auto [path, line] = [&] () -> std::pair<Path, uint32_t> {
+        const auto [path, line] = [&] () -> std::pair<SourcePath, uint32_t> {
             if (v.type() == nPath || v.type() == nString) {
                 PathSet context;
                 auto path = state->coerceToPath(noPos, v, context, "while evaluating the filename to edit");
                 return {path, 0};
             } else if (v.isLambda()) {
                 auto pos = state->positions[v.lambda.fun->pos];
-                if (auto path = std::get_if<Path>(&pos.origin))
+                if (auto path = std::get_if<SourcePath>(&pos.origin))
                     return {*path, pos.line};
                 else
                     throw Error("'%s' cannot be shown in an editor", pos);
@@ -872,7 +872,7 @@ void NixRepl::addVarToScope(const Symbol name, Value & v)
 
 Expr * NixRepl::parseString(std::string s)
 {
-    Expr * e = state->parseExprFromString(std::move(s), curDir, staticEnv);
+    Expr * e = state->parseExprFromString(std::move(s), state->rootPath(curDir), staticEnv);
     return e;
 }
 
@@ -930,7 +930,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
         break;
 
     case nPath:
-        str << ANSI_GREEN << v.path << ANSI_NORMAL; // !!! escaping?
+        str << ANSI_GREEN << v.path().to_string() << ANSI_NORMAL; // !!! escaping?
         break;
 
     case nNull:

src/libexpr/attr-path.cc

@@ -106,7 +106,7 @@ std::pair<Value *, PosIdx> findAlongAttrPath(EvalState & state, const std::strin
 }
 
 
-std::pair<std::string, uint32_t> findPackageFilename(EvalState & state, Value & v, std::string what)
+std::pair<SourcePath, uint32_t> findPackageFilename(EvalState & state, Value & v, std::string what)
 {
     Value * v2;
     try {
@@ -118,21 +118,25 @@ std::pair<std::string, uint32_t> findPackageFilename(EvalState & state, Value &
 
     // FIXME: is it possible to extract the Pos object instead of doing this
     //        toString + parsing?
-    auto pos = state.forceString(*v2, noPos, "while evaluating the 'meta.position' attribute of a derivation");
+    PathSet context;
+    auto path = state.coerceToPath(noPos, *v2, context, "while evaluating the 'meta.position' attribute of a derivation");
 
-    auto colon = pos.rfind(':');
-    if (colon == std::string::npos)
-        throw ParseError("cannot parse meta.position attribute '%s'", pos);
+    auto fn = path.path.abs();
+
+    auto fail = [fn]() {
+        throw ParseError("cannot parse 'meta.position' attribute '%s'", fn);
+    };
 
-    std::string filename(pos, 0, colon);
-    unsigned int lineno;
     try {
-        lineno = std::stoi(std::string(pos, colon + 1, std::string::npos));
+        auto colon = fn.rfind(':');
+        if (colon == std::string::npos) fail();
+        std::string filename(fn, 0, colon);
+        auto lineno = std::stoi(std::string(fn, colon + 1, std::string::npos));
+        return {SourcePath{path.accessor, CanonPath(fn.substr(0, colon))}, lineno};
     } catch (std::invalid_argument & e) {
-        throw ParseError("cannot parse line number '%s'", pos);
+        fail();
+        abort();
     }
-
-    return { std::move(filename), lineno };
 }
 
 

src/libexpr/attr-path.hh

@@ -17,7 +17,7 @@ std::pair<Value *, PosIdx> findAlongAttrPath(
     Value & vIn);
 
 /* Heuristic to find the filename and lineno or a nix value. */
-std::pair<std::string, uint32_t> findPackageFilename(EvalState & state, Value & v, std::string what);
+std::pair<SourcePath, uint32_t> findPackageFilename(EvalState & state, Value & v, std::string what);
 
 std::vector<Symbol> parseAttrPath(EvalState & state, std::string_view s);
 

src/libexpr/eval-cache.cc

@@ -442,8 +442,10 @@ Value & AttrCursor::forceValue()
         if (v.type() == nString)
             cachedValue = {root->db->setString(getKey(), v.string.s, v.string.context),
                            string_t{v.string.s, {}}};
-        else if (v.type() == nPath)
-            cachedValue = {root->db->setString(getKey(), v.path), string_t{v.path, {}}};
+        else if (v.type() == nPath) {
+            auto path = v.path().path;
+            cachedValue = {root->db->setString(getKey(), path.abs()), string_t{path.abs(), {}}};
+        }
         else if (v.type() == nBool)
             cachedValue = {root->db->setBool(getKey(), v.boolean), v.boolean};
         else if (v.type() == nInt)
@@ -580,7 +582,7 @@ std::string AttrCursor::getString()
     if (v.type() != nString && v.type() != nPath)
         root->state.error("'%s' is not a string but %s", getAttrPathStr()).debugThrow<TypeError>();
 
-    return v.type() == nString ? v.string.s : v.path;
+    return v.type() == nString ? v.string.s : v.path().to_string();
 }
 
 string_t AttrCursor::getStringWithContext()
@@ -622,7 +624,7 @@ string_t AttrCursor::getStringWithContext()
     if (v.type() == nString)
         return {v.string.s, v.getContext(*root->state.store)};
     else if (v.type() == nPath)
-        return {v.path, {}};
+        return {v.path().to_string(), {}};
     else
         root->state.error("'%s' is not a string but %s", getAttrPathStr()).debugThrow<TypeError>();
 }