[RFC 140 2a] pkgs/by-name: Enforce for new packages

pkgs/by-name/README.md

@@ -1,11 +1,9 @@
 # Name-based package directories
 
 The structure of this directory maps almost directly to top-level package attributes.
-This is the recommended way to add new top-level packages to Nixpkgs [when possible](#limitations).
+Add new top-level packages to Nixpkgs using this mechanism [whenever possible](#limitations).
 
-Packages found in the named-based structure do not need to be explicitly added to the
-`top-level/all-packages.nix` file unless they require overriding the default value
-of an implicit attribute (see below).
+Packages found in the name-based structure are automatically included, without needing to be added to `all-packages.nix`. However if the implicit attribute defaults need to be changed for a package, this [must still be declared in `all-packages.nix`](#changing-implicit-attribute-defaults).
 
 ## Example
 

pkgs/test/nixpkgs-check-by-name/README.md

@@ -45,6 +45,8 @@ The current ratchets are:
 
 - New manual definitions of `pkgs.${name}` (e.g. in `pkgs/top-level/all-packages.nix`) with `args = { }`
   (see [nix evaluation checks](#nix-evaluation-checks)) must not be introduced.
+- New top-level packages defined using `pkgs.callPackage` must be defined with a package directory.
+  - Once a top-level package uses `pkgs/by-name`, it also can't be moved back out of it.
 
 ## Development
 

pkgs/test/nixpkgs-check-by-name/default.nix

@@ -9,6 +9,7 @@
 }:
 let
   runtimeExprPath = ./src/eval.nix;
+  nixpkgsLibPath = ../../../lib;
   package =
     rustPlatform.buildRustPackage {
       name = "nixpkgs-check-by-name";
@@ -30,6 +31,8 @@ let
         export NIX_STATE_DIR=$TEST_ROOT/var/nix
         export NIX_STORE_DIR=$TEST_ROOT/store
 
+        export NIXPKGS_LIB_PATH=${nixpkgsLibPath}
+
         # Ensure that even if tests run in parallel, we don't get an error
         # We'd run into https://github.com/NixOS/nix/issues/2706 unless the store is initialised first
         nix-store --init
@@ -44,6 +47,7 @@ let
       '';
       passthru.shell = mkShell {
         env.NIX_CHECK_BY_NAME_EXPR_PATH = toString runtimeExprPath;
+        env.NIXPKGS_LIB_PATH = toString nixpkgsLibPath;
         inputsFrom = [ package ];
       };
     };

pkgs/test/nixpkgs-check-by-name/src/eval.nix

@@ -79,15 +79,37 @@ let
         };
       };
 
-  attrInfos = map (name: [
-    name
-    (
+  byNameAttrs = builtins.listToAttrs (map (name: {
+    inherit name;
+    value.ByName =
       if ! pkgs ? ${name} then
         { Missing = null; }
       else
-        { Existing = attrInfo name pkgs.${name}; }
-    )
-  ]) attrs;
+        { Existing = attrInfo name pkgs.${name}; };
+  }) attrs);
 
+  # Information on all attributes that exist but are not in pkgs/by-name.
+  # We need this to enforce pkgs/by-name for new packages
+  nonByNameAttrs = builtins.mapAttrs (name: value:
+    let
+      output = attrInfo name value;
+      result = builtins.tryEval (builtins.deepSeq output null);
+    in
+    {
+      NonByName =
+        if result.success then
+          { EvalSuccess = output; }
+        else
+          { EvalFailure = null; };
+    }
+  ) (builtins.removeAttrs pkgs attrs);
+
+  # All attributes
+  attributes = byNameAttrs // nonByNameAttrs;
 in
-attrInfos
+# We output them in the form [ [ <name> <value> ] ]` such that the Rust side
+# doesn't need to sort them again to get deterministic behavior (good for testing)
+map (name: [
+  name
+  attributes.${name}
+]) (builtins.attrNames attributes)

pkgs/test/nixpkgs-check-by-name/src/eval.rs

@@ -2,6 +2,8 @@ use crate::nixpkgs_problem::NixpkgsProblem;
 use crate::ratchet;
 use crate::structure;
 use crate::validation::{self, Validation::Success};
+use std::collections::HashMap;
+use std::ffi::OsString;
 use std::path::Path;
 
 use anyhow::Context;
@@ -11,6 +13,21 @@ use std::process;
 use tempfile::NamedTempFile;
 
 /// Attribute set of this structure is returned by eval.nix
+#[derive(Deserialize)]
+enum Attribute {
+    /// An attribute that should be defined via pkgs/by-name
+    ByName(ByNameAttribute),
+    /// An attribute not defined via pkgs/by-name
+    NonByName(NonByNameAttribute),
+}
+
+#[derive(Deserialize)]
+enum NonByNameAttribute {
+    /// The attribute doesn't evaluate
+    EvalFailure,
+    EvalSuccess(AttributeInfo),
+}
+
 #[derive(Deserialize)]
 enum ByNameAttribute {
     /// The attribute doesn't exist at all
@@ -56,7 +73,7 @@ enum CallPackageVariant {
 pub fn check_values(
     nixpkgs_path: &Path,
     package_names: Vec<String>,
-    eval_accessible_paths: &[&Path],
+    eval_nix_path: &HashMap<String, PathBuf>,
 ) -> validation::Result<ratchet::Nixpkgs> {
     // Write the list of packages we need to check into a temporary JSON file.
     // This can then get read by the Nix evaluation.
@@ -105,9 +122,13 @@ pub fn check_values(
         .arg(nixpkgs_path);
 
     // Also add extra paths that need to be accessible
-    for path in eval_accessible_paths {
+    for (name, path) in eval_nix_path {
         command.arg("-I");
-        command.arg(path);
+        let mut name_value = OsString::new();
+        name_value.push(name);
+        name_value.push("=");
+        name_value.push(path);
+        command.arg(name_value);
     }
     command.args(["-I", &expr_path]);
     command.arg(expr_path);
@@ -120,7 +141,7 @@ pub fn check_values(
         anyhow::bail!("Failed to run command {command:?}");
     }
     // Parse the resulting JSON value
-    let attributes: Vec<(String, ByNameAttribute)> = serde_json::from_slice(&result.stdout)
+    let attributes: Vec<(String, Attribute)> = serde_json::from_slice(&result.stdout)
         .with_context(|| {
             format!(
                 "Failed to deserialise {}",
@@ -133,30 +154,86 @@ pub fn check_values(
             let relative_package_file = structure::relative_file_for_package(&attribute_name);
 
             use ratchet::RatchetState::*;
+            use Attribute::*;
             use AttributeInfo::*;
             use ByNameAttribute::*;
             use CallPackageVariant::*;
+            use NonByNameAttribute::*;
 
             let check_result = match attribute_value {
-                Missing => NixpkgsProblem::UndefinedAttr {
+                // The attribute succeeds evaluation and is NOT defined in pkgs/by-name
+                NonByName(EvalSuccess(attribute_info)) => {
+                    let uses_by_name = match attribute_info {
+                        // In these cases the package doesn't qualify for being in pkgs/by-name,
+                        // so the UsesByName ratchet is already as tight as it can be
+                        NonAttributeSet => Success(Tight),
+                        NonCallPackage => Success(Tight),
+                        // This is an odd case when _internalCallByNamePackageFile is used to define a package.
+                        CallPackage(CallPackageInfo {
+                            call_package_variant: Auto,
+                            ..
+                        }) => NixpkgsProblem::InternalCallPackageUsed {
+                            attr_name: attribute_name.clone(),
+                        }
+                        .into(),
+                        // Only derivations can be in pkgs/by-name,
+                        // so this attribute doesn't qualify
+                        CallPackage(CallPackageInfo {
+                            is_derivation: false,
+                            ..
+                        }) => Success(Tight),
+
+                        // The case of an attribute that qualifies:
+                        // - Uses callPackage
+                        // - Is a derivation
+                        CallPackage(CallPackageInfo {
+                            is_derivation: true,
+                            call_package_variant: Manual { path, empty_arg },
+                        }) => Success(Loose(ratchet::UsesByName {
+                            call_package_path: path,
+                            empty_arg,
+                        })),
+                    };
+                    uses_by_name.map(|x| ratchet::Package {
+                        empty_non_auto_called: Tight,
+                        uses_by_name: x,
+                    })
+                }
+                NonByName(EvalFailure) => {
+                    // This is a bit of an odd case: We don't even _know_ whether this attribute
+                    // would qualify for using pkgs/by-name. We can either:
+                    // - Assume it's not using pkgs/by-name, which has the problem that if a
+                    //   package evaluation gets broken temporarily, the fix can remove it from
+                    //   pkgs/by-name again
+                    // - Assume it's using pkgs/by-name already, which has the problem that if a
+                    //   package evaluation gets broken temporarily, fixing it requires a move to
+                    //   pkgs/by-name
+                    // We choose the latter, since we want to move towards pkgs/by-name, not away
+                    // from it
+                    Success(ratchet::Package {
+                        empty_non_auto_called: Tight,
+                        uses_by_name: Tight,
+                    })
+                }
+                ByName(Missing) => NixpkgsProblem::UndefinedAttr {
                     relative_package_file: relative_package_file.clone(),
                     package_name: attribute_name.clone(),
                 }
                 .into(),
-                Existing(NonAttributeSet) => NixpkgsProblem::NonDerivation {
+                ByName(Existing(NonAttributeSet)) => NixpkgsProblem::NonDerivation {
                     relative_package_file: relative_package_file.clone(),
                     package_name: attribute_name.clone(),
                 }
                 .into(),
-                Existing(NonCallPackage) => NixpkgsProblem::WrongCallPackage {
+                ByName(Existing(NonCallPackage)) => NixpkgsProblem::WrongCallPackage {
                     relative_package_file: relative_package_file.clone(),
                     package_name: attribute_name.clone(),
                 }
                 .into(),
-                Existing(CallPackage(CallPackageInfo {
+                ByName(Existing(CallPackage(CallPackageInfo {
                     is_derivation,
                     call_package_variant,
-                })) => {
+                }))) => {
                     let check_result = if !is_derivation {
                         NixpkgsProblem::NonDerivation {
                             relative_package_file: relative_package_file.clone(),
@@ -170,6 +247,7 @@ pub fn check_values(
                     check_result.and(match &call_package_variant {
                         Auto => Success(ratchet::Package {
                             empty_non_auto_called: Tight,
+                            uses_by_name: Tight,
                         }),
                         Manual { path, empty_arg } => {
                             let correct_file = if let Some(call_package_path) = path {
@@ -186,6 +264,7 @@ pub fn check_values(
                                     } else {
                                         Tight
                                     },
+                                    uses_by_name: Tight,
                                 })
                             } else {
                                 NixpkgsProblem::WrongCallPackage {
@@ -203,7 +282,7 @@ pub fn check_values(
     ));
 
     Ok(check_result.map(|elems| ratchet::Nixpkgs {
-        package_names,
+        package_names: elems.iter().map(|(name, _)| name.to_owned()).collect(),
         package_map: elems.into_iter().collect(),
     }))
 }

pkgs/test/nixpkgs-check-by-name/src/main.rs

@@ -12,6 +12,7 @@ use crate::validation::Validation::Success;
 use anyhow::Context;
 use clap::Parser;
 use colored::Colorize;
+use std::collections::HashMap;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::process::ExitCode;
@@ -44,7 +45,12 @@ pub struct Args {
 
 fn main() -> ExitCode {
     let args = Args::parse();
-    match process(&args.base, &args.nixpkgs, &[], &mut io::stderr()) {
+    match process(
+        &args.base,
+        &args.nixpkgs,
+        &HashMap::new(),
+        &mut io::stderr(),
+    ) {
         Ok(true) => {
             eprintln!("{}", "Validated successfully".green());
             ExitCode::SUCCESS
@@ -77,15 +83,15 @@ fn main() -> ExitCode {
 pub fn process<W: io::Write>(
     base_nixpkgs: &Path,
     main_nixpkgs: &Path,
-    eval_accessible_paths: &[&Path],
+    eval_nix_path: &HashMap<String, PathBuf>,
     error_writer: &mut W,
 ) -> anyhow::Result<bool> {
     // Check the main Nixpkgs first
-    let main_result = check_nixpkgs(main_nixpkgs, eval_accessible_paths, error_writer)?;
+    let main_result = check_nixpkgs(main_nixpkgs, eval_nix_path, error_writer)?;
     let check_result = main_result.result_map(|nixpkgs_version| {
         // If the main Nixpkgs doesn't have any problems, run the ratchet checks against the base
         // Nixpkgs
-        check_nixpkgs(base_nixpkgs, eval_accessible_paths, error_writer)?.result_map(
+        check_nixpkgs(base_nixpkgs, eval_nix_path, error_writer)?.result_map(
             |base_nixpkgs_version| {
                 Ok(ratchet::Nixpkgs::compare(
                     base_nixpkgs_version,
@@ -113,7 +119,7 @@ pub fn process<W: io::Write>(
 /// ratchet check against another result.
 pub fn check_nixpkgs<W: io::Write>(
     nixpkgs_path: &Path,
-    eval_accessible_paths: &[&Path],
+    eval_nix_path: &HashMap<String, PathBuf>,
     error_writer: &mut W,
 ) -> validation::Result<ratchet::Nixpkgs> {
     Ok({
@@ -134,7 +140,7 @@ pub fn check_nixpkgs<W: io::Write>(
         } else {
             check_structure(&nixpkgs_path)?.result_map(|package_names|
                 // Only if we could successfully parse the structure, we do the evaluation checks
-                eval::check_values(&nixpkgs_path, package_names, eval_accessible_paths))?
+                eval::check_values(&nixpkgs_path, package_names, eval_nix_path))?
         }
     })
 }
@@ -144,8 +150,10 @@ mod tests {
     use crate::process;
     use crate::utils;
     use anyhow::Context;
+    use std::collections::HashMap;
     use std::fs;
     use std::path::Path;
+    use std::path::PathBuf;
     use tempfile::{tempdir_in, TempDir};
 
     #[test]
@@ -226,7 +234,19 @@ mod tests {
     }
 
     fn test_nixpkgs(name: &str, path: &Path, expected_errors: &str) -> anyhow::Result<()> {
-        let extra_nix_path = Path::new("tests/mock-nixpkgs.nix");
+        let eval_nix_path = HashMap::from([
+            (
+                "test-nixpkgs".to_string(),
+                PathBuf::from("tests/mock-nixpkgs.nix"),
+            ),
+            (
+                "test-nixpkgs/lib".to_string(),
+                PathBuf::from(
+                    std::env::var("NIXPKGS_LIB_PATH")
+                        .with_context(|| "Could not get environment variable NIXPKGS_LIB_PATH")?,
+                ),
+            ),
+        ]);
 
         let base_path = path.join("base");
         let base_nixpkgs = if base_path.exists() {
@@ -238,7 +258,7 @@ mod tests {
         // We don't want coloring to mess up the tests
         let writer = temp_env::with_var("NO_COLOR", Some("1"), || -> anyhow::Result<_> {
             let mut writer = vec![];
-            process(base_nixpkgs, &path, &[&extra_nix_path], &mut writer)
+            process(base_nixpkgs, &path, &eval_nix_path, &mut writer)
                 .with_context(|| format!("Failed test case {name}"))?;
             Ok(writer)
         })?;