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lix/src/nix/repl.cc
Maximilian Bosch 2aeb874e83
Improve help-message for nix-repl 
* Remove obsolete `printHelp` function
* Add an example to demonstrate how to list all available commands
  within the REPL
2020-05-01 23:32:01 +02:00

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#include <iostream>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <setjmp.h>
#ifdef READLINE
#include <readline/history.h>
#include <readline/readline.h>
#else
// editline < 1.15.2 don't wrap their API for C++ usage
// (added in https://github.com/troglobit/editline/commit/91398ceb3427b730995357e9d120539fb9bb7461).
// This results in linker errors due to to name-mangling of editline C symbols.
// For compatibility with these versions, we wrap the API here
// (wrapping multiple times on newer versions is no problem).
extern "C" {
#include <editline.h>
}
#endif
#include "shared.hh"
#include "eval.hh"
#include "eval-inline.hh"
#include "attr-path.hh"
#include "store-api.hh"
#include "common-eval-args.hh"
#include "get-drvs.hh"
#include "derivations.hh"
#include "affinity.hh"
#include "globals.hh"
#include "command.hh"
#include "finally.hh"
#define GC_INCLUDE_NEW
#include <gc/gc_cpp.h>
namespace nix {
#define ESC_RED "\033[31m"
#define ESC_GRE "\033[32m"
#define ESC_YEL "\033[33m"
#define ESC_BLU "\033[34;1m"
#define ESC_MAG "\033[35m"
#define ESC_CYA "\033[36m"
#define ESC_END "\033[0m"
struct NixRepl : gc
{
string curDir;
std::unique_ptr<EvalState> state;
Bindings * autoArgs;
Strings loadedFiles;
const static int envSize = 32768;
StaticEnv staticEnv;
Env * env;
int displ;
StringSet varNames;
const Path historyFile;
NixRepl(const Strings & searchPath, nix::ref<Store> store);
~NixRepl();
void mainLoop(const std::vector<std::string> & files);
StringSet completePrefix(string prefix);
bool getLine(string & input, const std::string &prompt);
Path getDerivationPath(Value & v);
bool processLine(string line);
void loadFile(const Path & path);
void initEnv();
void reloadFiles();
void addAttrsToScope(Value & attrs);
void addVarToScope(const Symbol & name, Value & v);
Expr * parseString(string s);
void evalString(string s, Value & v);
typedef set<Value *> ValuesSeen;
std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth);
std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth, ValuesSeen & seen);
};
string removeWhitespace(string s)
{
s = chomp(s);
size_t n = s.find_first_not_of(" \n\r\t");
if (n != string::npos) s = string(s, n);
return s;
}
NixRepl::NixRepl(const Strings & searchPath, nix::ref<Store> store)
: state(std::make_unique<EvalState>(searchPath, store))
, staticEnv(false, &state->staticBaseEnv)
, historyFile(getDataDir() + "/nix/repl-history")
{
curDir = absPath(".");
}
NixRepl::~NixRepl()
{
write_history(historyFile.c_str());
}
static NixRepl * curRepl; // ugly
static char * completionCallback(char * s, int *match) {
auto possible = curRepl->completePrefix(s);
if (possible.size() == 1) {
*match = 1;
auto *res = strdup(possible.begin()->c_str() + strlen(s));
if (!res) throw Error("allocation failure");
return res;
} else if (possible.size() > 1) {
auto checkAllHaveSameAt = [&](size_t pos) {
auto &first = *possible.begin();
for (auto &p : possible) {
if (p.size() <= pos || p[pos] != first[pos])
return false;
}
return true;
};
size_t start = strlen(s);
size_t len = 0;
while (checkAllHaveSameAt(start + len)) ++len;
if (len > 0) {
*match = 1;
auto *res = strdup(std::string(*possible.begin(), start, len).c_str());
if (!res) throw Error("allocation failure");
return res;
}
}
*match = 0;
return nullptr;
}
static int listPossibleCallback(char *s, char ***avp) {
auto possible = curRepl->completePrefix(s);
if (possible.size() > (INT_MAX / sizeof(char*)))
throw Error("too many completions");
int ac = 0;
char **vp = nullptr;
auto check = [&](auto *p) {
if (!p) {
if (vp) {
while (--ac >= 0)
free(vp[ac]);
free(vp);
}
throw Error("allocation failure");
}
return p;
};
vp = check((char **)malloc(possible.size() * sizeof(char*)));
for (auto & p : possible)
vp[ac++] = check(strdup(p.c_str()));
*avp = vp;
return ac;
}
namespace {
// Used to communicate to NixRepl::getLine whether a signal occurred in ::readline.
volatile sig_atomic_t g_signal_received = 0;
void sigintHandler(int signo) {
g_signal_received = signo;
}
}
void NixRepl::mainLoop(const std::vector<std::string> & files)
{
string error = ANSI_RED "error:" ANSI_NORMAL " ";
std::cout << "Welcome to Nix version " << nixVersion << ". Type :? for help." << std::endl << std::endl;
for (auto & i : files)
loadedFiles.push_back(i);
reloadFiles();
if (!loadedFiles.empty()) std::cout << std::endl;
// Allow nix-repl specific settings in .inputrc
rl_readline_name = "nix-repl";
createDirs(dirOf(historyFile));
#ifndef READLINE
el_hist_size = 1000;
#endif
read_history(historyFile.c_str());
curRepl = this;
#ifndef READLINE
rl_set_complete_func(completionCallback);
rl_set_list_possib_func(listPossibleCallback);
#endif
std::string input;
while (true) {
// When continuing input from previous lines, don't print a prompt, just align to the same
// number of chars as the prompt.
if (!getLine(input, input.empty() ? "nix-repl> " : " "))
break;
try {
if (!removeWhitespace(input).empty() && !processLine(input)) return;
} catch (ParseError & e) {
if (e.msg().find("unexpected $end") != std::string::npos) {
// For parse errors on incomplete input, we continue waiting for the next line of
// input without clearing the input so far.
continue;
} else {
printMsg(lvlError, format(error + "%1%%2%") % (settings.showTrace ? e.prefix() : "") % e.msg());
}
} catch (Error & e) {
printMsg(lvlError, format(error + "%1%%2%") % (settings.showTrace ? e.prefix() : "") % e.msg());
} catch (Interrupted & e) {
printMsg(lvlError, format(error + "%1%%2%") % (settings.showTrace ? e.prefix() : "") % e.msg());
}
// We handled the current input fully, so we should clear it
// and read brand new input.
input.clear();
std::cout << std::endl;
}
}
bool NixRepl::getLine(string & input, const std::string &prompt)
{
struct sigaction act, old;
sigset_t savedSignalMask, set;
auto setupSignals = [&]() {
act.sa_handler = sigintHandler;
sigfillset(&act.sa_mask);
act.sa_flags = 0;
if (sigaction(SIGINT, &act, &old))
throw SysError("installing handler for SIGINT");
sigemptyset(&set);
sigaddset(&set, SIGINT);
if (sigprocmask(SIG_UNBLOCK, &set, &savedSignalMask))
throw SysError("unblocking SIGINT");
};
auto restoreSignals = [&]() {
if (sigprocmask(SIG_SETMASK, &savedSignalMask, nullptr))
throw SysError("restoring signals");
if (sigaction(SIGINT, &old, 0))
throw SysError("restoring handler for SIGINT");
};
setupSignals();
char * s = readline(prompt.c_str());
Finally doFree([&]() { free(s); });
restoreSignals();
if (g_signal_received) {
g_signal_received = 0;
input.clear();
return true;
}
if (!s)
return false;
input += s;
input += '\n';
return true;
}
StringSet NixRepl::completePrefix(string prefix)
{
StringSet completions;
size_t start = prefix.find_last_of(" \n\r\t(){}[]");
std::string prev, cur;
if (start == std::string::npos) {
prev = "";
cur = prefix;
} else {
prev = std::string(prefix, 0, start + 1);
cur = std::string(prefix, start + 1);
}
size_t slash, dot;
if ((slash = cur.rfind('/')) != string::npos) {
try {
auto dir = std::string(cur, 0, slash);
auto prefix2 = std::string(cur, slash + 1);
for (auto & entry : readDirectory(dir == "" ? "/" : dir)) {
if (entry.name[0] != '.' && hasPrefix(entry.name, prefix2))
completions.insert(prev + dir + "/" + entry.name);
}
} catch (Error &) {
}
} else if ((dot = cur.rfind('.')) == string::npos) {
/* This is a variable name; look it up in the current scope. */
StringSet::iterator i = varNames.lower_bound(cur);
while (i != varNames.end()) {
if (string(*i, 0, cur.size()) != cur) break;
completions.insert(prev + *i);
i++;
}
} else {
try {
/* This is an expression that should evaluate to an
attribute set. Evaluate it to get the names of the
attributes. */
string expr(cur, 0, dot);
string cur2 = string(cur, dot + 1);
Expr * e = parseString(expr);
Value v;
e->eval(*state, *env, v);
state->forceAttrs(v);
for (auto & i : *v.attrs) {
string name = i.name;
if (string(name, 0, cur2.size()) != cur2) continue;
completions.insert(prev + expr + "." + name);
}
} catch (ParseError & e) {
// Quietly ignore parse errors.
} catch (EvalError & e) {
// Quietly ignore evaluation errors.
} catch (UndefinedVarError & e) {
// Quietly ignore undefined variable errors.
}
}
return completions;
}
static int runProgram(const string & program, const Strings & args)
{
Strings args2(args);
args2.push_front(program);
Pid pid;
pid = fork();
if (pid == -1) throw SysError("forking");
if (pid == 0) {
restoreAffinity();
execvp(program.c_str(), stringsToCharPtrs(args2).data());
_exit(1);
}
return pid.wait();
}
bool isVarName(const string & s)
{
if (s.size() == 0) return false;
char c = s[0];
if ((c >= '0' && c <= '9') || c == '-' || c == '\'') return false;
for (auto & i : s)
if (!((i >= 'a' && i <= 'z') ||
(i >= 'A' && i <= 'Z') ||
(i >= '0' && i <= '9') ||
i == '_' || i == '-' || i == '\''))
return false;
return true;
}
Path NixRepl::getDerivationPath(Value & v) {
auto drvInfo = getDerivation(*state, v, false);
if (!drvInfo)
throw Error("expression does not evaluate to a derivation, so I can't build it");
Path drvPath = drvInfo->queryDrvPath();
if (drvPath == "" || !state->store->isValidPath(state->store->parseStorePath(drvPath)))
throw Error("expression did not evaluate to a valid derivation");
return drvPath;
}
bool NixRepl::processLine(string line)
{
if (line == "") return true;
string command, arg;
if (line[0] == ':') {
size_t p = line.find_first_of(" \n\r\t");
command = string(line, 0, p);
if (p != string::npos) arg = removeWhitespace(string(line, p));
} else {
arg = line;
}
if (command == ":?" || command == ":help") {
std::cout
<< "The following commands are available:\n"
<< "\n"
<< " <expr> Evaluate and print expression\n"
<< " <x> = <expr> Bind expression to variable\n"
<< " :a <expr> Add attributes from resulting set to scope\n"
<< " :b <expr> Build derivation\n"
<< " :e <expr> Open the derivation in $EDITOR\n"
<< " :i <expr> Build derivation, then install result into current profile\n"
<< " :l <path> Load Nix expression and add it to scope\n"
<< " :p <expr> Evaluate and print expression recursively\n"
<< " :q Exit nix-repl\n"
<< " :r Reload all files\n"
<< " :s <expr> Build dependencies of derivation, then start nix-shell\n"
<< " :t <expr> Describe result of evaluation\n"
<< " :u <expr> Build derivation, then start nix-shell\n";
}
else if (command == ":a" || command == ":add") {
Value v;
evalString(arg, v);
addAttrsToScope(v);
}
else if (command == ":l" || command == ":load") {
state->resetFileCache();
loadFile(arg);
}
else if (command == ":r" || command == ":reload") {
state->resetFileCache();
reloadFiles();
}
else if (command == ":e" || command == ":edit") {
Value v;
evalString(arg, v);
Pos pos;
if (v.type == tPath || v.type == tString) {
PathSet context;
auto filename = state->coerceToString(noPos, v, context);
pos.file = state->symbols.create(filename);
} else if (v.type == tLambda) {
pos = v.lambda.fun->pos;
} else {
// assume it's a derivation
pos = findDerivationFilename(*state, v, arg);
}
// Open in EDITOR
auto args = editorFor(pos);
auto editor = args.front();
args.pop_front();
runProgram(editor, args);
// Reload right after exiting the editor
state->resetFileCache();
reloadFiles();
}
else if (command == ":t") {
Value v;
evalString(arg, v);
std::cout << showType(v) << std::endl;
} else if (command == ":u") {
Value v, f, result;
evalString(arg, v);
evalString("drv: (import <nixpkgs> {}).runCommand \"shell\" { buildInputs = [ drv ]; } \"\"", f);
state->callFunction(f, v, result, Pos());
Path drvPath = getDerivationPath(result);
runProgram(settings.nixBinDir + "/nix-shell", Strings{drvPath});
}
else if (command == ":b" || command == ":i" || command == ":s") {
Value v;
evalString(arg, v);
Path drvPath = getDerivationPath(v);
if (command == ":b") {
/* We could do the build in this process using buildPaths(),
but doing it in a child makes it easier to recover from
problems / SIGINT. */
if (runProgram(settings.nixBinDir + "/nix", Strings{"build", "--no-link", drvPath}) == 0) {
auto drv = readDerivation(*state->store, drvPath);
std::cout << std::endl << "this derivation produced the following outputs:" << std::endl;
for (auto & i : drv.outputs)
std::cout << fmt(" %s -> %s\n", i.first, state->store->printStorePath(i.second.path));
}
} else if (command == ":i") {
runProgram(settings.nixBinDir + "/nix-env", Strings{"-i", drvPath});
} else {
runProgram(settings.nixBinDir + "/nix-shell", Strings{drvPath});
}
}
else if (command == ":p" || command == ":print") {
Value v;
evalString(arg, v);
printValue(std::cout, v, 1000000000) << std::endl;
}
else if (command == ":q" || command == ":quit")
return false;
else if (command != "")
throw Error(format("unknown command '%1%'") % command);
else {
size_t p = line.find('=');
string name;
if (p != string::npos &&
p < line.size() &&
line[p + 1] != '=' &&
isVarName(name = removeWhitespace(string(line, 0, p))))
{
Expr * e = parseString(string(line, p + 1));
Value & v(*state->allocValue());
v.type = tThunk;
v.thunk.env = env;
v.thunk.expr = e;
addVarToScope(state->symbols.create(name), v);
} else {
Value v;
evalString(line, v);
printValue(std::cout, v, 1) << std::endl;
}
}
return true;
}
void NixRepl::loadFile(const Path & path)
{
loadedFiles.remove(path);
loadedFiles.push_back(path);
Value v, v2;
state->evalFile(lookupFileArg(*state, path), v);
state->autoCallFunction(*autoArgs, v, v2);
addAttrsToScope(v2);
}
void NixRepl::initEnv()
{
env = &state->allocEnv(envSize);
env->up = &state->baseEnv;
displ = 0;
staticEnv.vars.clear();
varNames.clear();
for (auto & i : state->staticBaseEnv.vars)
varNames.insert(i.first);
}
void NixRepl::reloadFiles()
{
initEnv();
Strings old = loadedFiles;
loadedFiles.clear();
bool first = true;
for (auto & i : old) {
if (!first) std::cout << std::endl;
first = false;
std::cout << format("Loading '%1%'...") % i << std::endl;
loadFile(i);
}
}
void NixRepl::addAttrsToScope(Value & attrs)
{
state->forceAttrs(attrs);
for (auto & i : *attrs.attrs)
addVarToScope(i.name, *i.value);
std::cout << format("Added %1% variables.") % attrs.attrs->size() << std::endl;
}
void NixRepl::addVarToScope(const Symbol & name, Value & v)
{
if (displ >= envSize)
throw Error("environment full; cannot add more variables");
staticEnv.vars[name] = displ;
env->values[displ++] = &v;
varNames.insert((string) name);
}
Expr * NixRepl::parseString(string s)
{
Expr * e = state->parseExprFromString(s, curDir, staticEnv);
return e;
}
void NixRepl::evalString(string s, Value & v)
{
Expr * e = parseString(s);
e->eval(*state, *env, v);
state->forceValue(v);
}
std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int maxDepth)
{
ValuesSeen seen;
return printValue(str, v, maxDepth, seen);
}
std::ostream & printStringValue(std::ostream & str, const char * string) {
str << "\"";
for (const char * i = string; *i; i++)
if (*i == '\"' || *i == '\\') str << "\\" << *i;
else if (*i == '\n') str << "\\n";
else if (*i == '\r') str << "\\r";
else if (*i == '\t') str << "\\t";
else str << *i;
str << "\"";
return str;
}
// FIXME: lot of cut&paste from Nix's eval.cc.
std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int maxDepth, ValuesSeen & seen)
{
str.flush();
checkInterrupt();
state->forceValue(v);
switch (v.type) {
case tInt:
str << ESC_CYA << v.integer << ESC_END;
break;
case tBool:
str << ESC_CYA << (v.boolean ? "true" : "false") << ESC_END;
break;
case tString:
str << ESC_YEL;
printStringValue(str, v.string.s);
str << ESC_END;
break;
case tPath:
str << ESC_GRE << v.path << ESC_END; // !!! escaping?
break;
case tNull:
str << ESC_CYA "null" ESC_END;
break;
case tAttrs: {
seen.insert(&v);
bool isDrv = state->isDerivation(v);
if (isDrv) {
str << "«derivation ";
Bindings::iterator i = v.attrs->find(state->sDrvPath);
PathSet context;
Path drvPath = i != v.attrs->end() ? state->coerceToPath(*i->pos, *i->value, context) : "???";
str << drvPath << "»";
}
else if (maxDepth > 0) {
str << "{ ";
typedef std::map<string, Value *> Sorted;
Sorted sorted;
for (auto & i : *v.attrs)
sorted[i.name] = i.value;
for (auto & i : sorted) {
if (isVarName(i.first))
str << i.first;
else
printStringValue(str, i.first.c_str());
str << " = ";
if (seen.find(i.second) != seen.end())
str << "«repeated»";
else
try {
printValue(str, *i.second, maxDepth - 1, seen);
} catch (AssertionError & e) {
str << ESC_RED "«error: " << e.msg() << "»" ESC_END;
}
str << "; ";
}
str << "}";
} else
str << "{ ... }";
break;
}
case tList1:
case tList2:
case tListN:
seen.insert(&v);
str << "[ ";
if (maxDepth > 0)
for (unsigned int n = 0; n < v.listSize(); ++n) {
if (seen.find(v.listElems()[n]) != seen.end())
str << "«repeated»";
else
try {
printValue(str, *v.listElems()[n], maxDepth - 1, seen);
} catch (AssertionError & e) {
str << ESC_RED "«error: " << e.msg() << "»" ESC_END;
}
str << " ";
}
else
str << "... ";
str << "]";
break;
case tLambda: {
std::ostringstream s;
s << v.lambda.fun->pos;
str << ESC_BLU "«lambda @ " << filterANSIEscapes(s.str()) << "»" ESC_END;
break;
}
case tPrimOp:
str << ESC_MAG "«primop»" ESC_END;
break;
case tPrimOpApp:
str << ESC_BLU "«primop-app»" ESC_END;
break;
case tFloat:
str << v.fpoint;
break;
default:
str << ESC_RED "«unknown»" ESC_END;
break;
}
return str;
}
struct CmdRepl : StoreCommand, MixEvalArgs
{
std::vector<std::string> files;
CmdRepl()
{
expectArgs("files", &files);
}
std::string description() override
{
return "start an interactive environment for evaluating Nix expressions";
}
Examples examples() override
{
return {
Example{
"Display all special commands within the REPL:",
"nix repl\n nix-repl> :?"
}
};
}
void run(ref<Store> store) override
{
auto repl = std::make_unique<NixRepl>(searchPath, openStore());
repl->autoArgs = getAutoArgs(*repl->state);
repl->mainLoop(files);
}
};
static auto r1 = registerCommand<CmdRepl>("repl");
}
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