Merge nix-repl repository

src/nix/repl.cc

@@ -0,0 +1,719 @@
+#include <nix/config.h>
+
+#include <iostream>
+#include <cstdlib>
+
+#include <setjmp.h>
+
+#include <readline/readline.h>
+#include <readline/history.h>
+
+#include "shared.hh"
+#include "eval.hh"
+#include "eval-inline.hh"
+#include "store-api.hh"
+#include "common-opts.hh"
+#include "get-drvs.hh"
+#include "derivations.hh"
+#include "affinity.hh"
+#include "globals.hh"
+
+using namespace std;
+using 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"
+
+string programId = "nix-repl";
+const string historyFile = string(getenv("HOME")) + "/.nix-repl-history";
+
+struct NixRepl
+{
+    string curDir;
+    EvalState state;
+
+    Strings loadedFiles;
+
+    const static int envSize = 32768;
+    StaticEnv staticEnv;
+    Env * env;
+    int displ;
+    StringSet varNames;
+
+    StringSet completions;
+    StringSet::iterator curCompletion;
+
+    NixRepl(const Strings & searchPath, nix::ref<Store> store);
+    void mainLoop(const Strings & files);
+    void completePrefix(string prefix);
+    bool getLine(string & input, const char * 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);
+};
+
+
+void printHelp()
+{
+    cout << "Usage: nix-repl [--help] [--version] [-I path] paths...\n"
+         << "\n"
+         << "nix-repl is a simple read-eval-print loop (REPL) for the Nix package manager.\n"
+         << "\n"
+         << "Options:\n"
+         << "    --help\n"
+         << "        Prints out a summary of the command syntax and exits.\n"
+         << "\n"
+         << "    --version\n"
+         << "        Prints out the Nix version number on standard output and exits.\n"
+         << "\n"
+         << "    -I path\n"
+         << "        Add a path to the Nix expression search path. This option may be given\n"
+         << "        multiple times. See the NIX_PATH environment variable for information on\n"
+         << "        the semantics of the Nix search path. Paths added through -I take\n"
+         << "        precedence over NIX_PATH.\n"
+         << "\n"
+         << "    paths...\n"
+         << "        A list of paths to files containing Nix expressions which nix-repl will\n"
+         << "        load and add to its scope.\n"
+         << "\n"
+         << "        A path surrounded in < and > will be looked up in the Nix expression search\n"
+         << "        path, as in the Nix language itself.\n"
+         << "\n"
+         << "        If an element of paths starts with http:// or https://, it is interpreted\n"
+         << "        as the URL of a tarball that will be downloaded and unpacked to a temporary\n"
+         << "        location. The tarball must include a single top-level directory containing\n"
+         << "        at least a file named default.nix.\n"
+         << flush;
+}
+
+
+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(searchPath, store)
+    , staticEnv(false, &state.staticBaseEnv)
+{
+    curDir = absPath(".");
+}
+
+
+void NixRepl::mainLoop(const Strings & files)
+{
+    string error = ANSI_RED "error:" ANSI_NORMAL " ";
+    std::cout << "Welcome to Nix version " << NIX_VERSION << ". 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";
+    using_history();
+    read_history(historyFile.c_str());
+
+    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.
+        const char * prompt = input.empty() ? "nix-repl> " : "          ";
+        if (!getLine(input, prompt)) {
+            std::cout << std::endl;
+            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;
+    }
+}
+
+
+/* Apparently, the only way to get readline() to return on Ctrl-C
+   (SIGINT) is to use siglongjmp().  That's fucked up... */
+static sigjmp_buf sigintJmpBuf;
+
+
+static void sigintHandler(int signo)
+{
+    siglongjmp(sigintJmpBuf, 1);
+}
+
+
+/* Oh, if only g++ had nested functions... */
+NixRepl * curRepl;
+
+char * completerThunk(const char * s, int state)
+{
+    string prefix(s);
+
+    /* If the prefix has a slash in it, use readline's builtin filename
+       completer. */
+    if (prefix.find('/') != string::npos)
+        return rl_filename_completion_function(s, state);
+
+    /* Otherwise, return all symbols that start with the prefix. */
+    if (state == 0) {
+        curRepl->completePrefix(s);
+        curRepl->curCompletion = curRepl->completions.begin();
+    }
+    if (curRepl->curCompletion == curRepl->completions.end()) return 0;
+    return strdup((curRepl->curCompletion++)->c_str());
+}
+
+
+bool NixRepl::getLine(string & input, const char * prompt)
+{
+    struct sigaction act, old;
+    act.sa_handler = sigintHandler;
+    sigfillset(&act.sa_mask);
+    act.sa_flags = 0;
+    if (sigaction(SIGINT, &act, &old))
+        throw SysError("installing handler for SIGINT");
+
+    if (sigsetjmp(sigintJmpBuf, 1)) {
+        input.clear();
+    } else {
+        curRepl = this;
+        rl_completion_entry_function = completerThunk;
+
+        char * s = readline(prompt);
+        if (!s) return false;
+        input.append(s);
+        input.push_back('\n');
+        if (!removeWhitespace(s).empty()) {
+            add_history(s);
+            append_history(1, 0);
+        }
+        free(s);
+    }
+
+    _isInterrupted = 0;
+
+    if (sigaction(SIGINT, &old, 0))
+        throw SysError("restoring handler for SIGINT");
+
+    return true;
+}
+
+
+void NixRepl::completePrefix(string prefix)
+{
+    completions.clear();
+
+    size_t dot = prefix.rfind('.');
+
+    if (dot == string::npos) {
+        /* This is a variable name; look it up in the current scope. */
+        StringSet::iterator i = varNames.lower_bound(prefix);
+        while (i != varNames.end()) {
+            if (string(*i, 0, prefix.size()) != prefix) break;
+            completions.insert(*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(prefix, 0, dot);
+            string prefix2 = string(prefix, 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, prefix2.size()) != prefix2) continue;
+                completions.insert(expr + "." + name);
+            }
+
+        } catch (ParseError & e) {
+            // Quietly ignore parse errors.
+        } catch (EvalError & e) {
+            // Quietly ignore evaluation errors.
+        } catch (UndefinedVarError & e) {
+            // Quietly ignore undefined variable errors.
+        }
+    }
+}
+
+
+static int runProgram(const string & program, const Strings & args)
+{
+    std::vector<const char *> cargs; /* careful with c_str()! */
+    cargs.push_back(program.c_str());
+    for (Strings::const_iterator i = args.begin(); i != args.end(); ++i)
+        cargs.push_back(i->c_str());
+    cargs.push_back(0);
+
+    Pid pid;
+    pid = fork();
+    if (pid == -1) throw SysError("forking");
+    if (pid == 0) {
+        restoreAffinity();
+        execvp(program.c_str(), (char * *) &cargs[0]);
+        _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) {
+    DrvInfo drvInfo(state);
+    if (!getDerivation(state, v, drvInfo, false))
+        throw Error("expression does not evaluate to a derivation, so I can't build it");
+    Path drvPath = drvInfo.queryDrvPath();
+    if (drvPath == "" || !state.store->isValidPath(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") {
+        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"
+             << "  :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 == ":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("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("nix-store", Strings{"-r", drvPath}) == 0) {
+                Derivation drv = readDerivation(drvPath);
+                std::cout << std::endl << "this derivation produced the following outputs:" << std::endl;
+                for (auto & i : drv.outputs)
+                    std::cout << format("  %1% -> %2%") % i.first % i.second.path << std::endl;
+            }
+        } else if (command == ":i") {
+            runProgram("nix-env", Strings{"-i", drvPath});
+        } else {
+            runProgram("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);
+    Bindings & bindings(*state.allocBindings(0));
+    state.autoCallFunction(bindings, 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;
+
+            /* If this is a derivation, then don't show the
+               self-references ("all", "out", etc.). */
+            StringSet hidden;
+            if (isDrv) {
+                hidden.insert("all");
+                Bindings::iterator i = v.attrs->find(state.sOutputs);
+                if (i == v.attrs->end())
+                    hidden.insert("out");
+                else {
+                    state.forceList(*i->value);
+                    for (unsigned int j = 0; j < i->value->listSize(); ++j)
+                        hidden.insert(state.forceStringNoCtx(*i->value->listElems()[j]));
+                }
+            }
+
+            for (auto & i : sorted) {
+                if (isVarName(i.first))
+                    str << i.first;
+                else
+                    printStringValue(str, i.first.c_str());
+                str << " = ";
+                if (hidden.find(i.first) != hidden.end())
+                    str << "«...»";
+                else 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;
+
+    default:
+        str << ESC_RED "«unknown»" ESC_END;
+        break;
+    }
+
+    return str;
+}
+
+
+int main(int argc, char * * argv)
+{
+    return handleExceptions(argv[0], [&]() {
+        initNix();
+        initGC();
+
+        Strings files, searchPath;
+
+        parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
+            if (*arg == "--version")
+                printVersion("nix-repl");
+            else if (*arg == "--help") {
+                printHelp();
+                // exit with 0 since user asked for help
+                _exit(0);
+            }
+            else if (parseSearchPathArg(arg, end, searchPath))
+                ;
+            else if (*arg != "" && arg->at(0) == '-')
+                return false;
+            else
+                files.push_back(*arg);
+            return true;
+        });
+
+        NixRepl repl(searchPath, openStore());
+        repl.mainLoop(files);
+
+        write_history(historyFile.c_str());
+    });
+}