From 519d541fdc71508793ece6e087d2c1a231378558 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 14:45:45 +0100
Subject: [PATCH 01/10] 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 59162c4df03..7dc3f7435ee 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -778,8 +778,11 @@ 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 29b83de5671901e5e8755c17b840139a6f8650db Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 14:46:17 +0100
Subject: [PATCH 02/10] 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 7dc3f7435ee..43e759b3e93 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -767,7 +767,7 @@ 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 9e9d28496a7216a0e2893ac0eb05a8c45d898c95 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 23:51:16 +0100
Subject: [PATCH 03/10] 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 43e759b3e93..1abad72e333 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -779,10 +779,54 @@ 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 e3045be11cbac91a5e65ef42e42e320e6689e713 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Wed, 20 Jul 2022 23:56:09 +0100
Subject: [PATCH 04/10] 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 d48682a9432..b5bee708451 100644
--- a/src/nix/nix.md
+++ b/src/nix/nix.md
@@ -139,8 +139,13 @@ 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 4d6c60a8187d9904312d062a19e61ca5c338bc94 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Thu, 21 Jul 2022 21:49:44 +0100
Subject: [PATCH 05/10] 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 1abad72e333..15679590e39 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -820,13 +820,15 @@ 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 14084facbd5654fa9e406ce0391c0544f3a42763 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Fri, 22 Jul 2022 14:28:31 +0100
Subject: [PATCH 06/10] 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 15679590e39..fee419b240a 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -754,7 +754,7 @@ 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;
 
@@ -780,7 +780,7 @@ 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) {
@@ -827,8 +827,8 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                         state, *this, vFile,
                         prefix == "." ? "" : prefix,
                         outputsSpec));
-                return result;
             }
+            return result;
         }
 
         for (auto & s : ss) {
@@ -1094,11 +1094,12 @@ 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 f82a172cfe18af507fadac565223769af2a39d86 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Fri, 22 Jul 2022 20:13:48 +0100
Subject: [PATCH 07/10] 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 fee419b240a..3073b153568 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -767,7 +767,7 @@ 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();
@@ -780,7 +780,7 @@ 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) {
@@ -796,7 +796,7 @@ 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),
@@ -804,10 +804,11 @@ 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 b5bee708451..33d618d88ad 100644
--- a/src/nix/nix.md
+++ b/src/nix/nix.md
@@ -145,8 +145,6 @@ 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 91da7d50e7ba52b846fa50b8e106d723380b08d5 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Sat, 23 Jul 2022 11:46:07 +0100
Subject: [PATCH 08/10] 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 3073b153568..d20ce6ed618 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -806,9 +806,18 @@ 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 a126a92e4f2c6087bf46dfb8c4acd5c34e5422eb Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Sun, 24 Jul 2022 01:30:00 +0100
Subject: [PATCH 09/10] 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 d20ce6ed618..9c8a848d641 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -816,7 +816,7 @@ 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 c7302640120ff9fff6c3a653c22fa678efbeb903 Mon Sep 17 00:00:00 2001
From: Skyler Grey <skyler3665@gmail.com>
Date: Sun, 24 Jul 2022 07:11:37 +0100
Subject: [PATCH 10/10] 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 9c8a848d641..bdc3830956a 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -816,7 +816,7 @@ 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 (...) {