f-f · Jan 24, 2026 · Mar 29, 2026 · thomashoneyman · Oct 22, 2026 · thomashoneyman
diff --git a/README.md b/README.md
@@ -121,6 +121,7 @@ Where to go from here? There are a few places you should check out:
   - [Override a package in the package set with a remote one](#override-a-package-in-the-package-set-with-a-remote-one)
   - [Add a package to the package set](#add-a-package-to-the-package-set)
   - [Querying package sets](#querying-package-sets)
+  - [Querying package information](#querying-package-information)
   - [Upgrading packages and the package set](#upgrading-packages-and-the-package-set)
   - [Custom package sets](#custom-package-sets)
   - [Graph the project modules and dependencies](#graph-the-project-modules-and-dependencies)
@@ -615,6 +616,57 @@ $ spago registry package-sets --latest
 +---------+------------+----------+
 ```
 
+You can also list all the packages contained in a specific package set by providing the set version as an argument:
+
+```console
+$ spago registry package-sets 0.0.1
++------------------------------+---------+
+| PACKAGE                      | VERSION |
++------------------------------+---------+
+| ace                          | 9.0.0   |
+| aff                          | 7.1.0   |
+| aff-bus                      | 6.0.0   |
+...
+```
+
+This is useful to check what version of a package is included in a specific set, or to explore the contents of an older set. The `--json` flag is available for machine-friendly output.
+
+### Querying package information
+
+To get detailed information about a package from the Registry, use `spago registry info`:
+
+```console
+$ spago registry info aff
+```
+
+This will print the package metadata (location, published versions, etc.) as YAML, followed by a table showing which package sets contain each published version of the package:
+
+```
+location:
+  githubOwner: purescript-contrib
+  githubRepo: purescript-aff
+published:
+  7.1.0:
+    bytes: 44616
+    hash: sha256-...
+    publishedTime: 2022-05-12T16:39:07.000Z
+    ref: v7.1.0
+...
+
+Package Sets containing each version:
++---------+-------------------------------+
+| VERSION | PACKAGE SETS                  |
++---------+-------------------------------+
+| 7.1.0   | 0.0.1, 0.0.2, 0.1.0, ...      |
++---------+-------------------------------+
+```
+
+Use the `--json` flag to get the output in JSON format, which includes both the metadata and the package sets information in a structured format:
+
+```console
+$ spago registry info aff --json
+```
+
 ### Upgrading packages and the package set
 
 If your project is using the Registry solver (i.e. no package set and only version bounds), then running `spago upgrade`

diff --git a/bin/src/Flags.purs b/bin/src/Flags.purs
@@ -309,6 +309,14 @@ maybeSetVersion =
           <> O.help "Optional package set version to be used instead of the latest one"
       )
 
+maybePackageSetVersion :: Parser (Maybe String)
+maybePackageSetVersion =
+  OT.optional $
+    O.strArgument
+      ( O.metavar "SET"
+          <> O.help "Package set version to query"
+      )
+
 maybePackageName :: Parser (Maybe String)
 maybePackageName =
   OT.optional $

diff --git a/bin/src/Main.purs b/bin/src/Main.purs
@@ -463,6 +463,7 @@ registryPackageSetsArgsParser =
   Optparse.fromRecord
     { json: Flags.json
     , latest: Flags.latest
+    , set: Flags.maybePackageSetVersion
     }
 
 registryTransferArgsParser :: Parser RegistryTransferArgs

diff --git a/src/Spago/Command/Registry.purs b/src/Spago/Command/Registry.purs
@@ -95,49 +95,118 @@ info { package, json } = do
     Left err -> do
       logDebug err
       die $ "Could not find package " <> PackageName.print packageName
-    Right meta -> do
-      -- We just print out the metadata file
-      output case json of
-        true -> OutputJson Metadata.codec meta
-        false -> OutputYaml Metadata.codec meta
+    Right meta@(Metadata.Metadata { published }) -> do
+      -- Get package sets for each published version
+      { db } <- ask
+      let versions = Array.fromFoldable $ Map.keys published
+      packageSetsByVersion <- for versions \version -> do
+        entries <- liftEffect $ Db.selectPackageSetEntriesByPackage db packageName version
+        let setVersions = map _.packageSetVersion entries
+        pure { version, packageSets: Array.sort setVersions }
+
+      case json of
+        true -> do
+          -- For JSON, we include package sets in a combined output
+          let
+            versionSetsCodec = CJ.named "VersionPackageSets" $ CJ.Record.object
+              { version: Version.codec
+              , packageSets: CJ.array Version.codec
+              }
+            combinedCodec = CJ.named "PackageInfoWithSets" $ CJ.Record.object
+              { metadata: Metadata.codec
+              , packageSets: CJ.array versionSetsCodec
+              }
+          output $ OutputJson combinedCodec { metadata: meta, packageSets: packageSetsByVersion }
+        false -> do
+          -- For YAML/text output, print metadata then add package sets table
+          output $ OutputYaml Metadata.codec meta
+          -- Only show the package sets table if there are any
+          let nonEmptySets = Array.filter (\r -> not (Array.null r.packageSets)) packageSetsByVersion
+          when (not (Array.null nonEmptySets)) do
+            logInfo ""
+            logInfo "Package Sets containing each version:"
+            output $ OutputTable
+              { titles: [ "VERSION", "PACKAGE SETS" ]
+              , rows: nonEmptySets # map \{ version, packageSets: sets } ->
+                  [ Version.print version
+                  , String.joinWith ", " (map Version.print sets)
+                  ]
+              }
 
 type RegistryPackageSetsArgs =
   { latest :: Boolean
   , json :: Boolean
+  , set :: Maybe String
   }
 
 packageSets :: ∀ r. RegistryPackageSetsArgs -> Spago (RegistryEnv r) Unit
-packageSets { latest, json } = do
-  availableSets <- Registry.listPackageSets
+packageSets { latest, json, set } = do
+  case set of
+    Just setVersionStr -> do
+      -- Query packages in a specific package set
+      setVersion <- case parseLenientVersion setVersionStr of
+        Left err -> die [ "Could not parse package set version. Error:", show err ]
+        Right v -> pure v
 
-  let
-    sets = case latest of
-      false -> availableSets
-      true ->
-        -- here we need to keep only the highest version of all the sets with the same compiler version
-        Array.fromFoldable
-          $ Map.values
-          $
-            foldl
-              ( \acc newSet -> case Map.lookup newSet.compiler acc of
-                  Nothing -> Map.insert newSet.compiler newSet acc
-                  Just { version } -> case newSet.version > version of
-                    true -> Map.insert newSet.compiler newSet acc
-                    false -> acc
-              )
-              Map.empty
-              availableSets
-
-  output case json of
-    true -> OutputJson (CJ.array Db.packageSetCodec) sets
-    false -> OutputTable
-      { titles: [ "VERSION", "DATE", "COMPILER" ]
-      , rows: sets # map \{ version, date, compiler } ->
-          [ Version.print version
-          , DateTime.format Internal.Format.iso8601Date $ DateTime date bottom
-          , Version.print compiler
-          ]
-      }
+      { db } <- ask
+      entries <- liftEffect $ Db.selectPackageSetEntriesBySet db setVersion
+
+      when (Array.null entries) do
+        die $ "No packages found in package set " <> Version.print setVersion
+
+      -- Sort entries by package name for consistent output
+      let sortedEntries = Array.sortWith _.packageName entries
+
+      output case json of
+        true ->
+          let
+            entryCodec = CJ.named "PackageSetEntryOutput" $ CJ.Record.object
+              { packageName: PackageName.codec
+              , packageVersion: Version.codec
+              }
+            toOutput e = { packageName: e.packageName, packageVersion: e.packageVersion }
+          in
+            OutputJson (CJ.array entryCodec) (map toOutput sortedEntries)
+        false -> OutputTable
+          { titles: [ "PACKAGE", "VERSION" ]
+          , rows: sortedEntries # map \{ packageName, packageVersion } ->
+              [ PackageName.print packageName
+              , Version.print packageVersion
+              ]
+          }
+
+    Nothing -> do
+      -- Original behavior: list all package sets
+      availableSets <- Registry.listPackageSets
+
+      let
+        sets = case latest of
+          false -> availableSets
+          true ->
+            -- here we need to keep only the highest version of all the sets with the same compiler version
+            Array.fromFoldable
+              $ Map.values
+              $
+                foldl
+                  ( \acc newSet -> case Map.lookup newSet.compiler acc of
+                      Nothing -> Map.insert newSet.compiler newSet acc
+                      Just { version } -> case newSet.version > version of
+                        true -> Map.insert newSet.compiler newSet acc
+                        false -> acc
+                  )
+                  Map.empty
+                  availableSets
+
+      output case json of
+        true -> OutputJson (CJ.array Db.packageSetCodec) sets
+        false -> OutputTable
+          { titles: [ "VERSION", "DATE", "COMPILER" ]
+          , rows: sets # map \{ version, date, compiler } ->
+              [ Version.print version
+              , DateTime.format Internal.Format.iso8601Date $ DateTime date bottom
+              , Version.print compiler
+              ]
+          }
 
 type RegistryTransferArgs = { privateKeyPath :: RawFilePath }
 

diff --git a/src/Spago/Db.purs b/src/Spago/Db.purs
@@ -14,8 +14,11 @@ module Spago.Db
   , insertPackageSet
   , insertPackageSetEntry
   , packageSetCodec
+  , packageSetEntryCodec
   , selectLatestPackageSetByCompiler
   , selectPackageSets
+  , selectPackageSetEntriesBySet
+  , selectPackageSetEntriesByPackage
   , updateLastPull
   , withTransaction
   ) where
@@ -74,10 +77,6 @@ selectLatestPackageSetByCompiler db compiler = do
   maybePackageSet <- Nullable.toMaybe <$> Uncurried.runEffectFn2 selectLatestPackageSetByCompilerImpl db (Version.print compiler)
   pure $ packageSetFromJs =<< maybePackageSet
 
-{-
-
-We'll need these when implementing a command for "show me what's in this package set"
-
 selectPackageSetEntriesBySet :: Db -> Version -> Effect (Array PackageSetEntry)
 selectPackageSetEntriesBySet db packageSetVersion = do
   packageSetEntries <- Uncurried.runEffectFn2 selectPackageSetEntriesBySetImpl db (Version.print packageSetVersion)
@@ -87,7 +86,6 @@ selectPackageSetEntriesByPackage :: Db -> PackageName -> Version -> Effect (Arra
 selectPackageSetEntriesByPackage db packageName version = do
   packageSetEntries <- Uncurried.runEffectFn3 selectPackageSetEntriesByPackageImpl db (PackageName.print packageName) (Version.print version)
   pure $ Array.mapMaybe packageSetEntryFromJs packageSetEntries
--}
 
 getLastPull :: Db -> String -> Effect (Maybe DateTime)
 getLastPull db key = do
@@ -212,17 +210,13 @@ packageSetEntryToJs { packageSetVersion, packageName, packageVersion } =
   , packageVersion: Version.print packageVersion
   }
 
-{-
-
 packageSetEntryFromJs :: PackageSetEntryJs -> Maybe PackageSetEntry
 packageSetEntryFromJs p = hush do
   packageSetVersion <- Version.parse p.packageSetVersion
   packageName <- PackageName.parse p.packageName
   packageVersion <- Version.parse p.packageVersion
   pure $ { packageSetVersion, packageName, packageVersion }
 
--}
-
 --------------------------------------------------------------------------------
 -- Codecs
 
@@ -233,6 +227,13 @@ packageSetCodec = CJ.named "PackageSet" $ CJ.Record.object
   , compiler: Version.codec
   }
 
+packageSetEntryCodec :: CJ.Codec PackageSetEntry
+packageSetEntryCodec = CJ.named "PackageSetEntry" $ CJ.Record.object
+  { packageSetVersion: Version.codec
+  , packageName: PackageName.codec
+  , packageVersion: Version.codec
+  }
+
 --------------------------------------------------------------------------------
 -- FFI
 

diff --git a/test-fixtures/registry-package-set-0.0.1.txt b/test-fixtures/registry-package-set-0.0.1.txt
@@ -0,0 +1,50 @@
++------------------------------+---------+
+| PACKAGE                      | VERSION |
++------------------------------+---------+
+| ace                          | 9.0.0   |
+| aff                          | 7.1.0   |
+| aff-bus                      | 6.0.0   |
+| aff-coroutines               | 9.0.0   |
+| aff-promise                  | 4.0.0   |
+| aff-retry                    | 2.0.0   |
+| affjax                       | 13.0.0  |
+| affjax-node                  | 1.0.0   |
+| affjax-web                   | 1.0.0   |
+| ansi                         | 7.0.0   |
+| argonaut                     | 9.0.0   |
+| argonaut-codecs              | 9.1.0   |
+| argonaut-core                | 7.0.0   |
+| argonaut-generic             | 8.0.0   |
+| argonaut-traversals          | 10.0.0  |
+| argparse-basic               | 2.0.0   |
+| array-builder                | 0.1.2   |
+| arraybuffer                  | 13.0.0  |
+| arraybuffer-builder          | 3.0.1   |
+| arraybuffer-types            | 3.0.2   |
+| arrays                       | 7.1.0   |
+| arrays-zipper                | 2.0.1   |
+| ask                          | 1.0.0   |
+| assert                       | 6.0.0   |
+| avar                         | 5.0.0   |
+| b64                          | 0.0.8   |
+| barbies                      | 1.0.1   |
+| barlow-lens                  | 0.9.0   |
+| bifunctors                   | 6.0.0   |
+| bigints                      | 7.0.1   |
+| bolson                       | 0.1.1   |
+| bower-json                   | 3.0.0   |
+| call-by-name                 | 4.0.1   |
+| canvas                       | 6.0.0   |
+| canvas-action                | 9.0.0   |
+| cartesian                    | 1.0.6   |
+| catenable-lists              | 7.0.0   |
+| channel                      | 1.0.0   |
+| checked-exceptions           | 3.1.1   |
+| classnames                   | 2.0.0   |
+| codec                        | 5.0.0   |
+| codec-argonaut               | 9.0.0   |
+| colors                       | 7.0.1   |
+| concur-core                  | 0.5.0   |
+| concur-react                 | 0.5.0   |
+| concurrent-queues            | 3.0.0   |
+| console                      | 6.0.0   |
diff --git a/test/Spago/Registry.purs b/test/Spago/Registry.purs
@@ -35,3 +35,28 @@ spec = Spec.parallel $ Spec.around withTempDir do
               # String.joinWith "\n"
           }
       shouldBeSuccessOutput (fixture "registry-list-package-sets-latest.txt") $ bimap updateStdout updateStdout result
+
+    Spec.it "query package sets and package info with set associations" \{ spago, fixture } -> do
+      -- Test: List packages in a specific package set (table output)
+      do
+        result <- spago [ "registry", "package-sets", "0.0.1" ]
+        let
+          updateStdout r = r
+            { stdout = r.stdout
+                # String.split (Pattern "\n")
+                # Array.take 50
+                # String.joinWith "\n"
+            }
+        shouldBeSuccessOutput (fixture "registry-package-set-0.0.1.txt") $ bimap updateStdout updateStdout result
+
+      -- Test: List packages in a specific package set (JSON output)
+      spago [ "registry", "package-sets", "0.0.1", "--json" ] >>= shouldBeSuccess
+
+      -- Test: Error for non-existent package set version
+      spago [ "registry", "package-sets", "999.999.999" ] >>= shouldBeFailure
+
+      -- Test: Info command shows package sets for versions (text output)
+      spago [ "registry", "info", "prelude" ] >>= shouldBeSuccess
+
+      -- Test: Info command with JSON includes package sets
+      spago [ "registry", "info", "prelude", "--json" ] >>= shouldBeSuccess