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Add repl-overlays

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Adds a `repl-overlays` option, which specifies files that can overlay
and modify the top-level bindings in `nix repl`. For example, with the
following contents in `~/.config/nix/repl.nix`:

    info: final: prev: let
      optionalAttrs = predicate: attrs:
        if predicate
        then attrs
        else {};
    in
      optionalAttrs (prev ? legacyPackages && prev.legacyPackages ? ${info.currentSystem})
      {
        pkgs = prev.legacyPackages.${info.currentSystem};
      }

We can run `nix repl` and use `pkgs` to refer to `legacyPackages.${currentSystem}`:

    $ nix repl --repl-overlays ~/.config/nix/repl.nix nixpkgs
    Nix 2.21.0pre20240309_4111bb6
    Type :? for help.
    Loading installable 'flake:nixpkgs#'...
    Added 5 variables.
    Loading 'repl-overlays'...
    Added 6 variables.
    nix-repl> pkgs.bash
    «derivation /nix/store/g08b5vkwwh0j8ic9rkmd8mpj878rk62z-bash-5.2p26.drv»

Change-Id: Ic12e0f2f210b2f46e920c33088dfe1083f42391a
This commit is contained in:
Rebecca Turner 2024-03-14 11:31:22 -07:00
parent f3b71e1e62
commit efb15e3dd5
16 changed files with 307 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

35
doc/manual/rl-next/repl-overlays.md Normal file
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@ -0,0 +1,35 @@
---
synopsis: Add `repl-overlays` option
prs: 10203
---
A `repl-overlays` option has been added, which specifies files that can overlay
and modify the top-level bindings in `nix repl`. For example, with the
following contents in `~/.config/nix/repl.nix`:
```nix
info: final: prev: let
optionalAttrs = predicate: attrs:
if predicate
then attrs
else {};
in
optionalAttrs (prev ? legacyPackages && prev.legacyPackages ? ${info.currentSystem})
{
pkgs = prev.legacyPackages.${info.currentSystem};
}
```
We can run `nix repl` and use `pkgs` to refer to `legacyPackages.${currentSystem}`:
```ShellSession
$ nix repl --repl-overlays ~/.config/nix/repl.nix nixpkgs
Nix 2.21.0pre20240309_4111bb6
Type :? for help.
Loading installable 'flake:nixpkgs#'...
Added 5 variables.
Loading 'repl-overlays'...
Added 6 variables.
nix-repl> pkgs.bash
«derivation /nix/store/g08b5vkwwh0j8ic9rkmd8mpj878rk62z-bash-5.2p26.drv»
```

2
src/libcmd/local.mk
View file

@ -13,3 +13,5 @@ libcmd_LDFLAGS = $(EDITLINE_LIBS) $(LOWDOWN_LIBS) -pthread
libcmd_LIBS = libstore libutil libexpr libmain libfetchers
$(eval $(call install-file-in, $(buildprefix)$(d)/nix-cmd.pc, $(libdir)/pkgconfig, 0644))
$(d)/repl.cc: $(d)/repl-overlays.nix.gen.hh

8
src/libcmd/repl-overlays.nix Normal file
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@ -0,0 +1,8 @@
info:
initial:
functions:
let final = builtins.foldl'
(prev: function: prev // (function info final prev))
initial
functions;
in final

143
src/libcmd/repl.cc
View file

@ -30,6 +30,7 @@
#include "signals.hh"
#include "print.hh"
#include "progress-bar.hh"
#include "gc-small-vector.hh"
#if HAVE_BOEHMGC
#define GC_INCLUDE_NEW
@ -100,6 +101,42 @@ struct NixRepl
void evalString(std::string s, Value & v);
void loadDebugTraceEnv(DebugTrace & dt);
/**
* Load the `repl-overlays` and add the resulting AttrSet to the top-level
* bindings.
*/
void loadReplOverlays();
/**
* Get a list of each of the `repl-overlays` (parsed and evaluated).
*/
Value * replOverlays();
/**
* Get the Nix function that composes the `repl-overlays` together.
*/
Value * getReplOverlaysEvalFunction();
/**
* Cached return value of `getReplOverlaysEvalFunction`.
*/
Value * replOverlaysEvalFunction;
/**
* Get the `info` AttrSet that's passed as the first argument to each
* of the `repl-overlays`.
*/
Value * replInitInfo();
/**
* Get the current top-level bindings as an AttrSet.
*/
Value * bindingsToAttrs();
/**
* Parse a file, evaluate its result, and force the resulting value.
*/
Value * evalFile(SourcePath & path);
void printValue(std::ostream & str,
Value & v,
unsigned int maxDepth = std::numeric_limits<unsigned int>::max())
@ -737,14 +774,95 @@ void NixRepl::loadFiles()
loadedFiles.clear();
for (auto & i : old) {
notice("Loading '%1%'...", i);
notice("Loading '%1%'...", Magenta(i));
loadFile(i);
}
for (auto & [i, what] : getValues()) {
notice("Loading installable '%1%'...", what);
notice("Loading installable '%1%'...", Magenta(what));
addAttrsToScope(*i);
}
loadReplOverlays();
}
void NixRepl::loadReplOverlays()
{
if (!evalSettings.replOverlays) {
return;
}
notice("Loading '%1%'...", Magenta("repl-overlays"));
auto replInitFilesFunction = getReplOverlaysEvalFunction();
Value &newAttrs(*state->allocValue());
SmallValueVector<3> args = {replInitInfo(), bindingsToAttrs(), replOverlays()};
state->callFunction(
*replInitFilesFunction,
args.size(),
args.data(),
newAttrs,
replInitFilesFunction->determinePos(noPos)
);
addAttrsToScope(newAttrs);
}
Value * NixRepl::getReplOverlaysEvalFunction()
{
if (replOverlaysEvalFunction) {
return replOverlaysEvalFunction;
}
auto evalReplInitFilesPath = CanonPath::root + "repl-overlays.nix";
replOverlaysEvalFunction = state->allocValue();
auto code =
#include "repl-overlays.nix.gen.hh"
;
auto expr = state->parseExprFromString(
code,
SourcePath(evalReplInitFilesPath),
state->staticBaseEnv
);
state->eval(expr, *replOverlaysEvalFunction);
return replOverlaysEvalFunction;
}
Value * NixRepl::replOverlays()
{
Value * replInits(state->allocValue());
state->mkList(*replInits, evalSettings.replOverlays.get().size());
Value ** replInitElems = replInits->listElems();
size_t i = 0;
for (auto path : evalSettings.replOverlays.get()) {
debug("Loading '%1%' path '%2%'...", "repl-overlays", path);
SourcePath sourcePath((CanonPath(path)));
replInitElems[i] = evalFile(sourcePath);
i++;
}
return replInits;
}
Value * NixRepl::replInitInfo()
{
auto builder = state->buildBindings(2);
Value * currentSystem(state->allocValue());
currentSystem->mkString(evalSettings.getCurrentSystem());
builder.insert(state->symbols.create("currentSystem"), currentSystem);
Value * valueNull(state->allocValue());
valueNull->mkNull();
builder.insert(state->symbols.create("__pleaseUseDotDotDot"), valueNull);
Value * info(state->allocValue());
info->mkAttrs(builder.finish());
return info;
}
@ -777,6 +895,18 @@ void NixRepl::addVarToScope(const Symbol name, Value & v)
varNames.emplace(state->symbols[name]);
}
Value * NixRepl::bindingsToAttrs()
{
auto builder = state->buildBindings(staticEnv->vars.size());
for (auto & [symbol, displacement] : staticEnv->vars) {
builder.insert(symbol, env->values[displacement]);
}
Value * attrs(state->allocValue());
attrs->mkAttrs(builder.finish());
return attrs;
}
Expr * NixRepl::parseString(std::string s)
{
@ -791,6 +921,15 @@ void NixRepl::evalString(std::string s, Value & v)
state->forceValue(v, v.determinePos(noPos));
}
Value * NixRepl::evalFile(SourcePath & path)
{
auto expr = state->parseExprFromFile(path, staticEnv);
Value * result(state->allocValue());
expr->eval(*state, *env, *result);
state->forceValue(*result, result->determinePos(noPos));
return result;
}
std::unique_ptr<AbstractNixRepl> AbstractNixRepl::create(
const SearchPath & searchPath, nix::ref<Store> store, ref<EvalState> state,

36
src/libexpr/eval-settings.hh
View file

@ -124,6 +124,42 @@ struct EvalSettings : Config
This is useful for debugging warnings in third-party Nix code.
)"};
PathsSetting replOverlays{this, Paths(), "repl-overlays",
R"(
A list of files containing Nix expressions that can be used to add
default bindings to [`nix
repl`](@docroot@/command-ref/new-cli/nix3-repl.md) sessions.
Each file is called with three arguments:
1. An [attribute set](@docroot@/language/values.html#attribute-set)
containing at least a
[`currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem)
attribute (this is identical to
[`builtins.currentSystem`](@docroot@/language/builtin-constants.md#builtins-currentSystem),
except that it's available in
[`pure-eval`](@docroot@/command-ref/conf-file.html#conf-pure-eval)
mode).
2. The top-level bindings produced by the previous `repl-overlays`
value (or the default top-level bindings).
3. The final top-level bindings produced by calling all
`repl-overlays`.
For example, the following file would alias `pkgs` to
`legacyPackages.${info.currentSystem}` (if that attribute is defined):
```nix
info: prev: final:
if prev ? legacyPackages
&& prev.legacyPackages ? ${info.currentSystem}
then
{
pkgs = prev.legacyPackages.${info.currentSystem};
}
else
{ }
```
)"};
};
extern EvalSettings evalSettings;

3
tests/functional/repl_characterization/data/repl_overlays.nix Normal file
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@ -0,0 +1,3 @@
{
packages.x86_64-linux.default = "my package";
}

5
tests/functional/repl_characterization/data/repl_overlays.test Normal file
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@ -0,0 +1,5 @@
Check basic `repl-overlays` functionality.
@args --repl-overlays
@args ${PWD}/../extra_data/repl-overlay-packages-is-pkgs.nix
nix-repl> pkgs
{ default = "my package"; }

3
tests/functional/repl_characterization/data/repl_overlays_compose.nix Normal file
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@ -0,0 +1,3 @@
{
var = "a";
}

7
tests/functional/repl_characterization/data/repl_overlays_compose.test Normal file
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@ -0,0 +1,7 @@
Check that multiple `repl-overlays` can compose together
@args --repl-overlays
@args "${PWD}/../extra_data/repl-overlays-compose-1.nix ${PWD}/../extra_data/repl-overlays-compose-2.nix"
nix-repl> var
"abc"
nix-repl> varUsingFinal
"final value is: puppy"

26
tests/functional/repl_characterization/data/repl_overlays_destructure_without_dotdotdot_errors.test Normal file
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@ -0,0 +1,26 @@
`repl-overlays` that try to parse out the `info` argument without a `...` error.
@args --repl-overlays
@args ${PWD}/../extra_data/repl-overlay-no-dotdotdot.nix
@should-start false
error:
… while calling the 'foldl'' builtin
at «string»:5:13:
4| functions:
5| let final = builtins.foldl'
| ^
6| (prev: function: prev // (function info final prev))
… in the right operand of the update (//) operator
at «string»:6:37:
5| let final = builtins.foldl'
6| (prev: function: prev // (function info final prev))
| ^
7| initial
(stack trace truncated; use '--show-trace' to show the full trace)
error: function 'anonymous lambda' called with unexpected argument '__pleaseUseDotDotDot'
at /Users/wiggles/lix/tests/functional/repl_characterization/extra_data/repl-overlay-no-dotdotdot.nix:1:1:
1| {currentSystem}: final: prev: {}
| ^
2|

22
tests/functional/repl_characterization/data/repl_overlays_error.test Normal file
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@ -0,0 +1,22 @@
`repl-overlays` that fail to evaluate should error.
@args --repl-overlays
@args ${PWD}/../extra_data/repl-overlay-fail.nix
@should-start false
error:
… while calling the 'foldl'' builtin
at «string»:5:13:
4| functions:
5| let final = builtins.foldl'
| ^
6| (prev: function: prev // (function info final prev))
… in the right operand of the update (//) operator
at «string»:6:37:
5| let final = builtins.foldl'
6| (prev: function: prev // (function info final prev))
| ^
7| initial
(stack trace truncated; use '--show-trace' to show the full trace)
error: evaluation aborted with the following error message: 'uh oh!'

1
tests/functional/repl_characterization/extra_data/repl-overlay-fail.nix Normal file
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@ -0,0 +1 @@
info: final: prev: builtins.abort "uh oh!"

1
tests/functional/repl_characterization/extra_data/repl-overlay-no-dotdotdot.nix Normal file
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@ -0,0 +1 @@
{currentSystem}: final: prev: {}

4
tests/functional/repl_characterization/extra_data/repl-overlay-packages-is-pkgs.nix Normal file
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@ -0,0 +1,4 @@
info: final: prev:
{
pkgs = final.packages.x86_64-linux;
}

7
tests/functional/repl_characterization/extra_data/repl-overlays-compose-1.nix Normal file
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@ -0,0 +1,7 @@
info: final: prev:
{
var = prev.var + "b";
# We can access the final value of `var` here even though it isn't defined yet:
varUsingFinal = "final value is: " + final.newVar;
}

6
tests/functional/repl_characterization/extra_data/repl-overlays-compose-2.nix Normal file
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@ -0,0 +1,6 @@
info: final: prev:
{
var = prev.var + "c";
newVar = "puppy";
}