Shellbang support with flakes

Enables shebang usage of nix shell. All arguments with `#! nix` get
added to the nix invocation. This implementation does NOT set any
additional arguments other than placing the script path itself as the
first argument such that the interpreter can utilize it.

Example below:

```
    #!/usr/bin/env nix
    #! nix shell --quiet
    #! nix nixpkgs#bash
    #! nix nixpkgs#shellcheck
    #! nix nixpkgs#hello
    #! nix --ignore-environment --command bash
    # shellcheck shell=bash
    set -eu
    shellcheck "$0" || exit 1
    function main {
        hello
        echo 0:"$0" 1:"$1" 2:"$2"
    }
    "$@"
```

fix: include programName usage

EDIT: For posterity I've changed shellwords to shellwords2 in order
      not to interfere with other changes during a rebase.
      shellwords2 is removed in a later commit. -- roberth
This commit is contained in:
Tom Bereknyei 2021-08-28 16:26:53 -04:00 committed by tomberek
parent ba4e07782c
commit 74210c12fe
7 changed files with 114 additions and 9 deletions

View file

@ -6,6 +6,7 @@
#include "users.hh" #include "users.hh"
#include "json-utils.hh" #include "json-utils.hh"
#include <regex>
#include <glob.h> #include <glob.h>
namespace nix { namespace nix {
@ -78,6 +79,12 @@ std::optional<std::string> RootArgs::needsCompletion(std::string_view s)
} }
void RootArgs::parseCmdline(const Strings & _cmdline) void RootArgs::parseCmdline(const Strings & _cmdline)
{
// Default via 5.1.2.2.1 in C standard
Args::parseCmdline("", _cmdline);
}
void Args::parseCmdline(const std::string & programName, const Strings & _cmdline)
{ {
Strings pendingArgs; Strings pendingArgs;
bool dashDash = false; bool dashDash = false;
@ -93,6 +100,36 @@ void RootArgs::parseCmdline(const Strings & _cmdline)
} }
bool argsSeen = false; bool argsSeen = false;
// Heuristic to see if we're invoked as a shebang script, namely,
// if we have at least one argument, it's the name of an
// executable file, and it starts with "#!".
Strings savedArgs;
auto isNixCommand = std::regex_search(programName, std::regex("nix$"));
if (isNixCommand && cmdline.size() > 0) {
auto script = *cmdline.begin();
try {
auto lines = tokenizeString<Strings>(readFile(script), "\n");
if (std::regex_search(lines.front(), std::regex("^#!"))) {
lines.pop_front();
for (auto pos = std::next(cmdline.begin()); pos != cmdline.end();pos++)
savedArgs.push_back(*pos);
cmdline.clear();
for (auto line : lines) {
line = chomp(line);
std::smatch match;
if (std::regex_match(line, match, std::regex("^#!\\s*nix\\s(.*)$")))
for (const auto & word : shellwords(match[1].str()))
cmdline.push_back(word);
}
cmdline.push_back(script);
for (auto pos = savedArgs.begin(); pos != savedArgs.end();pos++)
cmdline.push_back(*pos);
}
} catch (SysError &) { }
}
for (auto pos = cmdline.begin(); pos != cmdline.end(); ) { for (auto pos = cmdline.begin(); pos != cmdline.end(); ) {
auto arg = *pos; auto arg = *pos;

View file

@ -27,8 +27,14 @@ class Args
public: public:
/** /**
* Return a short one-line description of the command. * Parse the command line with argv0, throwing a UsageError if something
goes wrong.
*/ */
void parseCmdline(const std::string & argv0, const Strings & cmdline);
/**
* Return a short one-line description of the command.
*/
virtual std::string description() { return ""; } virtual std::string description() { return ""; }
virtual bool forceImpureByDefault() { return false; } virtual bool forceImpureByDefault() { return false; }

View file

@ -5,6 +5,8 @@
#include <cctype> #include <cctype>
#include <iostream> #include <iostream>
#include <grp.h> #include <grp.h>
#include <regex>
namespace nix { namespace nix {
@ -136,6 +138,49 @@ std::string shellEscape(const std::string_view s)
return r; return r;
} }
/* Recreate the effect of the perl shellwords function, breaking up a
* string into arguments like a shell word, including escapes
*/
std::vector<std::string> shellwords2(const std::string & s)
{
std::regex whitespace("^(\\s+).*");
auto begin = s.cbegin();
std::vector<std::string> res;
std::string cur;
enum state {
sBegin,
sQuote
};
state st = sBegin;
auto it = begin;
for (; it != s.cend(); ++it) {
if (st == sBegin) {
std::smatch match;
if (regex_search(it, s.cend(), match, whitespace)) {
cur.append(begin, it);
res.push_back(cur);
cur.clear();
it = match[1].second;
begin = it;
}
}
switch (*it) {
case '"':
cur.append(begin, it);
begin = it + 1;
st = st == sBegin ? sQuote : sBegin;
break;
case '\\':
/* perl shellwords mostly just treats the next char as part of the string with no special processing */
cur.append(begin, it);
begin = ++it;
break;
}
}
cur.append(begin, it);
if (!cur.empty()) res.push_back(cur);
return res;
}
void ignoreException(Verbosity lvl) void ignoreException(Verbosity lvl)
{ {

View file

@ -189,10 +189,13 @@ std::string toLower(const std::string & s);
std::string shellEscape(const std::string_view s); std::string shellEscape(const std::string_view s);
/** /* Recreate the effect of the perl shellwords function, breaking up a
* Exception handling in destructors: print an error message, then * string into arguments like a shell word, including escapes */
* ignore the exception. std::vector<std::string> shellwords2(const std::string & s);
*/
/* Exception handling in destructors: print an error message, then
ignore the exception. */
void ignoreException(Verbosity lvl = lvlError); void ignoreException(Verbosity lvl = lvlError);

View file

@ -428,7 +428,7 @@ void mainWrapped(int argc, char * * argv)
}); });
try { try {
args.parseCmdline(argvToStrings(argc, argv)); args.parseCmdline(programName, argvToStrings(argc, argv));
} catch (UsageError &) { } catch (UsageError &) {
if (!args.helpRequested && !args.completions) throw; if (!args.helpRequested && !args.completions) throw;
} }

View file

@ -11,6 +11,7 @@ writeSimpleFlake() {
outputs = inputs: rec { outputs = inputs: rec {
packages.$system = rec { packages.$system = rec {
foo = import ./simple.nix; foo = import ./simple.nix;
fooScript = (import ./shell.nix {}).foo;
default = foo; default = foo;
}; };
packages.someOtherSystem = rec { packages.someOtherSystem = rec {
@ -24,13 +25,13 @@ writeSimpleFlake() {
} }
EOF EOF
cp ../simple.nix ../simple.builder.sh ../config.nix $flakeDir/ cp ../simple.nix ../shell.nix ../simple.builder.sh ../config.nix $flakeDir/
} }
createSimpleGitFlake() { createSimpleGitFlake() {
local flakeDir="$1" local flakeDir="$1"
writeSimpleFlake $flakeDir writeSimpleFlake $flakeDir
git -C $flakeDir add flake.nix simple.nix simple.builder.sh config.nix git -C $flakeDir add flake.nix simple.nix shell.nix simple.builder.sh config.nix
git -C $flakeDir commit -m 'Initial' git -C $flakeDir commit -m 'Initial'
} }

View file

@ -66,7 +66,17 @@ cat > "$nonFlakeDir/README.md" <<EOF
FNORD FNORD
EOF EOF
git -C "$nonFlakeDir" add README.md cat > "$nonFlakeDir/shebang.sh" <<EOF
#! $(type -P env) nix
#! nix --offline shell
#! nix flake1#fooScript
#! nix --no-write-lock-file --command bash
set -e
foo
EOF
chmod +x "$nonFlakeDir/shebang.sh"
git -C "$nonFlakeDir" add README.md shebang.sh
git -C "$nonFlakeDir" commit -m 'Initial' git -C "$nonFlakeDir" commit -m 'Initial'
# Construct a custom registry, additionally test the --registry flag # Construct a custom registry, additionally test the --registry flag
@ -511,3 +521,6 @@ nix flake metadata "$flake2Dir" --reference-lock-file $TEST_ROOT/flake2-overridd
# reference-lock-file can only be used if allow-dirty is set. # reference-lock-file can only be used if allow-dirty is set.
expectStderr 1 nix flake metadata "$flake2Dir" --no-allow-dirty --reference-lock-file $TEST_ROOT/flake2-overridden.lock expectStderr 1 nix flake metadata "$flake2Dir" --no-allow-dirty --reference-lock-file $TEST_ROOT/flake2-overridden.lock
# Test shebang
[[ $($nonFlakeDir/shebang.sh) = "foo" ]]