From a54baf53d934a3c95bcc42bdbeaefca3cc12aab7 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 14:45:45 +0100
Subject: [PATCH 01/11] Make --expr always include nixpkgs

---
 src/libcmd/installables.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 60d6e9dc08c..e065f655452 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -788,8 +788,11 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         else if (file)
             state->evalFile(lookupFileArg(*state, *file), *vFile);
         else {
-            auto e = state->parseExprFromString(*expr, absPath("."));
-            state->eval(e, *vFile);
+            Strings e = {};
+            e.push_back("with (builtins.getFlake \"nixpkgs\")");
+            e.push_back(*expr);
+            auto parsed = state->parseExprFromString(concatStringsSep(";", e), absPath("."));
+            state->eval(parsed, *vFile);
         }
 
         for (auto & s : ss) {

From 8e2457a62ab209e1f111ab71aeaa694ad35fd0fd Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 14:46:17 +0100
Subject: [PATCH 02/11] Stop --expr requiring --impure flag

---
 src/libcmd/installables.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index e065f655452..fc83d6e35b8 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -776,7 +776,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             throw UsageError("'--file' and '--expr' are exclusive");
 
         // FIXME: backward compatibility hack
-        if (file) evalSettings.pureEval = false;
+        evalSettings.pureEval = false;
 
         auto state = getEvalState();
         auto vFile = state->allocValue();

From c2f7a39313ab34dc208fddc0a2467e7739bc3754 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 23:51:16 +0100
Subject: [PATCH 03/11] Make nix shell take installables as context

---
 src/libcmd/installables.cc | 46 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index fc83d6e35b8..477aa8cc760 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -789,10 +789,54 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             state->evalFile(lookupFileArg(*state, *file), *vFile);
         else {
             Strings e = {};
-            e.push_back("with (builtins.getFlake \"nixpkgs\")");
+
+            for (auto & s : ss) {
+                std::exception_ptr ex;
+
+                if (s.find('/') != std::string::npos) {
+                    try {
+                        result.push_back(std::make_shared<InstallableStorePath>(store, store->followLinksToStorePath(s)));
+                        continue;
+                    } catch (BadStorePath &) {
+                    } catch (...) {
+                        if (!ex)
+                            ex = std::current_exception();
+                    }
+                }
+
+                try {
+                    auto [flakeRef, fragment, outputsSpec] = parseFlakeRefWithFragmentAndOutputsSpec(s, absPath("."));
+/*                    result.push_back(std::make_shared<InstallableFlake>(
+                            this,
+                            getEvalState(),
+                            std::move(flakeRef),
+                            fragment,
+                            outputsSpec,
+                            getDefaultFlakeAttrPaths(),
+                            getDefaultFlakeAttrPathPrefixes(),
+                            lockFlags));*/
+                    e.push_back("with (builtins.getFlake \"" + flakeRef.to_string() + "\")" + (fragment != "" ? "." + fragment : ""));
+                    e.push_back("with (builtins.getFlake \"" + flakeRef.to_string() + "\").packages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
+                    e.push_back("with (builtins.getFlake \"" + flakeRef.to_string() + "\").legacyPackages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
+                    continue;
+                } catch (...) {
+                    ex = std::current_exception();
+                }
+
+                std::rethrow_exception(ex);
+            }
+
             e.push_back(*expr);
             auto parsed = state->parseExprFromString(concatStringsSep(";", e), absPath("."));
             state->eval(parsed, *vFile);
+
+            auto [prefix, outputsSpec] = parseOutputsSpec(".");
+            result.push_back(
+                std::make_shared<InstallableAttrPath>(
+                    state, *this, vFile,
+                    prefix == "." ? "" : prefix,
+                    outputsSpec));
+            return result;
         }
 
         for (auto & s : ss) {

From 2aaef9cd16698dd4c574c0c0fe6bc03394ef2296 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 23:56:09 +0100
Subject: [PATCH 04/11] Update documentation to match nix shell change

---
 src/nix/nix.md | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/nix/nix.md b/src/nix/nix.md
index db60c59ffaf..3491b38af23 100644
--- a/src/nix/nix.md
+++ b/src/nix/nix.md
@@ -138,8 +138,13 @@ the Nix store. Here are the recognised types of installables:
 * **Nix expressions**: `--expr '(import <nixpkgs> {}).hello.overrideDerivation (prev: { name = "my-hello"; })'`.
 
   When the `--expr` option is given, all installables are interpreted
-  as Nix expressions. You may need to specify `--impure` if the
-  expression references impure inputs (such as `<nixpkgs>`).
+  as context for the expression. For example, the following is valid:
+
+  ```console
+  # nix shell nixpkgs#python3 --expr 'withPackages(pyPkgs: with pyPkgs; [ numpy ])'
+  ```
+
+  Using `--expr` implies `--impure`.
 
 For most commands, if no installable is specified, the default is `.`,
 i.e. Nix will operate on the default flake output attribute of the

From 340051b4f71957bc93ec7ac6511657c4de6dc0ce Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Thu, 21 Jul 2022 21:49:44 +0100
Subject: [PATCH 05/11] Only build . with expr if it'd be a default installable

---
 src/libcmd/installables.cc | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 477aa8cc760..e82103422bf 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -830,13 +830,15 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             auto parsed = state->parseExprFromString(concatStringsSep(";", e), absPath("."));
             state->eval(parsed, *vFile);
 
-            auto [prefix, outputsSpec] = parseOutputsSpec(".");
-            result.push_back(
-                std::make_shared<InstallableAttrPath>(
-                    state, *this, vFile,
-                    prefix == "." ? "" : prefix,
-                    outputsSpec));
-            return result;
+            if (!ss.empty()) {
+                auto [prefix, outputsSpec] = parseOutputsSpec(".");
+                result.push_back(
+                    std::make_shared<InstallableAttrPath>(
+                        state, *this, vFile,
+                        prefix == "." ? "" : prefix,
+                        outputsSpec));
+                return result;
+            }
         }
 
         for (auto & s : ss) {

From 01426c7c8d76b57fd342d7e2ce4390c9dba92c27 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Fri, 22 Jul 2022 14:28:31 +0100
Subject: [PATCH 06/11] Do not include implicit installables with expr

---
 src/libcmd/command.hh      | 2 +-
 src/libcmd/installables.cc | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 3b4b40981de..ba6ab4197ad 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -102,7 +102,7 @@ struct SourceExprCommand : virtual Args, MixFlakeOptions
     SourceExprCommand(bool supportReadOnlyMode = false);
 
     std::vector<std::shared_ptr<Installable>> parseInstallables(
-        ref<Store> store, std::vector<std::string> ss);
+        ref<Store> store, std::vector<std::string> ss, std::optional<std::vector<std::string>> explicitInstallables);
 
     std::shared_ptr<Installable> parseInstallable(
         ref<Store> store, const std::string & installable);
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index e82103422bf..5c11c976299 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -763,7 +763,7 @@ FlakeRef InstallableFlake::nixpkgsFlakeRef() const
 }
 
 std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
-    ref<Store> store, std::vector<std::string> ss)
+    ref<Store> store, std::vector<std::string> ss, std::optional<std::vector<std::string>> explicitInstallables = std::nullopt)
 {
     std::vector<std::shared_ptr<Installable>> result;
 
@@ -790,7 +790,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         else {
             Strings e = {};
 
-            for (auto & s : ss) {
+            for (auto & s : explicitInstallables.value_or(ss)) {
                 std::exception_ptr ex;
 
                 if (s.find('/') != std::string::npos) {
@@ -837,8 +837,8 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                         state, *this, vFile,
                         prefix == "." ? "" : prefix,
                         outputsSpec));
-                return result;
             }
+            return result;
         }
 
         for (auto & s : ss) {
@@ -1132,11 +1132,12 @@ void InstallablesCommand::prepare()
 
 Installables InstallablesCommand::load() {
     Installables installables;
+    auto explicitInstallables = _installables;
     if (_installables.empty() && useDefaultInstallables())
         // FIXME: commands like "nix profile install" should not have a
         // default, probably.
         _installables.push_back(".");
-    return parseInstallables(getStore(), _installables);
+    return parseInstallables(getStore(), _installables, explicitInstallables);
 }
 
 std::vector<std::string> InstallablesCommand::getFlakesForCompletion()

From 82904ee72f245f4b901f8f9b94c4e9caff2b53be Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Fri, 22 Jul 2022 20:13:48 +0100
Subject: [PATCH 07/11] Allow running --expr purely again

---
 src/libcmd/installables.cc | 15 ++++++++-------
 src/nix/nix.md             |  2 --
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 5c11c976299..e54d4107353 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -776,7 +776,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             throw UsageError("'--file' and '--expr' are exclusive");
 
         // FIXME: backward compatibility hack
-        evalSettings.pureEval = false;
+        if (file) evalSettings.pureEval = false;
 
         auto state = getEvalState();
         auto vFile = state->allocValue();
@@ -790,7 +790,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
         else {
             Strings e = {};
 
-            for (auto & s : explicitInstallables.value_or(ss)) {
+            for (auto & s : explicitInstallables.value_or(std::vector<std::string>())) {
                 std::exception_ptr ex;
 
                 if (s.find('/') != std::string::npos) {
@@ -806,7 +806,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
 
                 try {
                     auto [flakeRef, fragment, outputsSpec] = parseFlakeRefWithFragmentAndOutputsSpec(s, absPath("."));
-/*                    result.push_back(std::make_shared<InstallableFlake>(
+                    auto installableFlake = InstallableFlake(
                             this,
                             getEvalState(),
                             std::move(flakeRef),
@@ -814,10 +814,11 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                             outputsSpec,
                             getDefaultFlakeAttrPaths(),
                             getDefaultFlakeAttrPathPrefixes(),
-                            lockFlags));*/
-                    e.push_back("with (builtins.getFlake \"" + flakeRef.to_string() + "\")" + (fragment != "" ? "." + fragment : ""));
-                    e.push_back("with (builtins.getFlake \"" + flakeRef.to_string() + "\").packages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
-                    e.push_back("with (builtins.getFlake \"" + flakeRef.to_string() + "\").legacyPackages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
+                            lockFlags);
+                    auto lockedFlake = installableFlake.getLockedFlake()->flake.lockedRef;
+                    e.push_back("with (builtins.getFlake \"" + lockedFlake.to_string() + "\")" + (fragment != "" ? "." + fragment : ""));
+                    e.push_back("with (builtins.getFlake \"" + lockedFlake.to_string() + "\").packages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
+                    e.push_back("with (builtins.getFlake \"" + lockedFlake.to_string() + "\").legacyPackages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
                     continue;
                 } catch (...) {
                     ex = std::current_exception();
diff --git a/src/nix/nix.md b/src/nix/nix.md
index 3491b38af23..2fdaf258643 100644
--- a/src/nix/nix.md
+++ b/src/nix/nix.md
@@ -144,8 +144,6 @@ the Nix store. Here are the recognised types of installables:
   # nix shell nixpkgs#python3 --expr 'withPackages(pyPkgs: with pyPkgs; [ numpy ])'
   ```
 
-  Using `--expr` implies `--impure`.
-
 For most commands, if no installable is specified, the default is `.`,
 i.e. Nix will operate on the default flake output attribute of the
 flake in the current directory.

From 60aeb420787c6276e26df6c73bd33d2a870590ef Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Sat, 23 Jul 2022 11:46:07 +0100
Subject: [PATCH 08/11] Fix builtins.currentSystem in pure evaluation

---
 src/libcmd/installables.cc | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index e54d4107353..95a31dba289 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -816,9 +816,18 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                             getDefaultFlakeAttrPathPrefixes(),
                             lockFlags);
                     auto lockedFlake = installableFlake.getLockedFlake()->flake.lockedRef;
-                    e.push_back("with (builtins.getFlake \"" + lockedFlake.to_string() + "\")" + (fragment != "" ? "." + fragment : ""));
-                    e.push_back("with (builtins.getFlake \"" + lockedFlake.to_string() + "\").packages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
-                    e.push_back("with (builtins.getFlake \"" + lockedFlake.to_string() + "\").legacyPackages.\"${builtins.currentSystem}\"" + (fragment != "" ? "." + fragment : ""));
+
+                    auto defaultPathPrefixes = getDefaultFlakeAttrPathPrefixes();
+                    defaultPathPrefixes.push_back("");
+
+                    for (auto & path : defaultPathPrefixes) {
+                        if (path.length()) {
+                            path.pop_back();
+                            path = "." + path;
+                        }
+
+                        e.push_back(str(boost::format("with (builtins.getFlake \"%1%\")%2%%3%") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
+                    }
                     continue;
                 } catch (...) {
                     ex = std::current_exception();

From ed9400560c79657b9d7a2e2952fb4effc6453928 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Sun, 24 Jul 2022 01:30:00 +0100
Subject: [PATCH 09/11] Gracefully handle missing attributes

---
 src/libcmd/installables.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 95a31dba289..419fc90c96a 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -826,7 +826,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                             path = "." + path;
                         }
 
-                        e.push_back(str(boost::format("with (builtins.getFlake \"%1%\")%2%%3%") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
+                        e.push_back(str(boost::format("with (builtins.getFlake \"%1%\")%2%%3% or {}") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
                     }
                     continue;
                 } catch (...) {

From 3fba464fe76656d54136ab757fc7ede579254a4e Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Sun, 24 Jul 2022 07:11:37 +0100
Subject: [PATCH 10/11] Fix including a flake without any attrpath

---
 src/libcmd/installables.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 419fc90c96a..bad324b424c 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -826,7 +826,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                             path = "." + path;
                         }
 
-                        e.push_back(str(boost::format("with (builtins.getFlake \"%1%\")%2%%3% or {}") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
+                        e.push_back(str(boost::format("with (builtins.getFlake \"%1%\").outputs%2%%3% or {}") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
                     }
                     continue;
                 } catch (...) {

From 8ad1e705394a304db09935c207a964de33c02c08 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Fri, 24 Feb 2023 01:09:56 +0000
Subject: [PATCH 11/11] Fix regressions in the patch due to nix changes

---
 src/libcmd/installables.cc | 48 +++++++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index bad324b424c..57c2492c106 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -791,11 +791,47 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             Strings e = {};
 
             for (auto & s : explicitInstallables.value_or(std::vector<std::string>())) {
+
+                auto [prefix_, extendedOutputsSpec_] = ExtendedOutputsSpec::parse(s);
+                // To avoid clang's pedantry
+                auto prefix = std::move(prefix_);
+                auto extendedOutputsSpec = std::move(extendedOutputsSpec_);
                 std::exception_ptr ex;
 
-                if (s.find('/') != std::string::npos) {
+                if (prefix.find('/') != std::string::npos) {
                     try {
-                        result.push_back(std::make_shared<InstallableStorePath>(store, store->followLinksToStorePath(s)));
+                        auto derivedPath = std::visit(overloaded {
+                            // If the user did not use ^, we treat the output more liberally.
+                            [&](const ExtendedOutputsSpec::Default &) -> DerivedPath {
+                                // First, we accept a symlink chain or an actual store path.
+                                auto storePath = store->followLinksToStorePath(prefix);
+                                // Second, we see if the store path ends in `.drv` to decide what sort
+                                // of derived path they want.
+                                //
+                                // This handling predates the `^` syntax. The `^*` in
+                                // `/nix/store/hash-foo.drv^*` unambiguously means "do the
+                                // `DerivedPath::Built` case", so plain `/nix/store/hash-foo.drv` could
+                                // also unambiguously mean "do the DerivedPath::Opaque` case".
+                                //
+                                // Issue #7261 tracks reconsidering this `.drv` dispatching.
+                                return storePath.isDerivation()
+                                    ? (DerivedPath) DerivedPath::Built {
+                                        .drvPath = std::move(storePath),
+                                        .outputs = OutputsSpec::All {},
+                                    }
+                                    : (DerivedPath) DerivedPath::Opaque {
+                                        .path = std::move(storePath),
+                                    };
+                            },
+                            // If the user did use ^, we just do exactly what is written.
+                            [&](const ExtendedOutputsSpec::Explicit & outputSpec) -> DerivedPath {
+                                return DerivedPath::Built {
+                                    .drvPath = store->parseStorePath(prefix),
+                                    .outputs = outputSpec,
+                                };
+                            },
+                        }, extendedOutputsSpec.raw());
+                        result.push_back(std::make_shared<InstallableStorePath>(store, std::move(derivedPath)));
                         continue;
                     } catch (BadStorePath &) {
                     } catch (...) {
@@ -805,7 +841,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                 }
 
                 try {
-                    auto [flakeRef, fragment, outputsSpec] = parseFlakeRefWithFragmentAndOutputsSpec(s, absPath("."));
+                    auto [flakeRef, fragment, outputsSpec] = parseFlakeRefWithFragmentAndExtendedOutputsSpec(s, absPath("."));
                     auto installableFlake = InstallableFlake(
                             this,
                             getEvalState(),
@@ -826,7 +862,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                             path = "." + path;
                         }
 
-                        e.push_back(str(boost::format("with (builtins.getFlake \"%1%\").outputs%2%%3% or {}") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
+                        e.push_back(boost::str(boost::format("with (builtins.getFlake \"%1%\").outputs%2%%3% or {}") % lockedFlake.to_string() % path % (fragment != "" ? "." + fragment : "")));
                     }
                     continue;
                 } catch (...) {
@@ -841,11 +877,11 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             state->eval(parsed, *vFile);
 
             if (!ss.empty()) {
-                auto [prefix, outputsSpec] = parseOutputsSpec(".");
+                auto [prefix, outputsSpec] = ExtendedOutputsSpec::parse(".");
                 result.push_back(
                     std::make_shared<InstallableAttrPath>(
                         state, *this, vFile,
-                        prefix == "." ? "" : prefix,
+                        prefix == "." ? "" : std::string { prefix },
                         outputsSpec));
             }
             return result;