Fix: resolve default HEAD refs in Solver::Graph

Author: ysbaddaden

src/solver/graph.cr

@@ -71,16 +71,25 @@ module Shards
       end
 
       private def versions_for(dependency, resolver) : Array(String)
-        if requirement = dependency.version?
-          if requirement == "HEAD"
-            versions_for_refs("HEAD", dependency, resolver)
+        matching =
+          if requirement = dependency.version?
+            if requirement == "HEAD"
+              return versions_for_refs("HEAD", dependency, resolver)
+            else
+              Versions.resolve(resolver.available_versions, requirement)
+            end
+          elsif refs = dependency.refs
+            versions_for_refs(refs, dependency, resolver)
           else
-            Versions.resolve(resolver.available_versions, requirement)
+            resolver.available_versions
           end
-        elsif refs = dependency.refs
-          versions_for_refs(refs, dependency, resolver)
+
+        if matching.size == 1 && matching.first == "HEAD"
+          # NOTE: dependency doesn't have any version number tag, and defaults
+          #       to [HEAD], we must resolve the refs to an actual version:
+          versions_for_refs("HEAD", dependency, resolver)
         else
-          resolver.available_versions
+          matching
         end
       end
 

test/integration/install_test.cr

@@ -109,6 +109,12 @@ class InstallCommandTest < Minitest::Test
     end
   end
 
+  def test_resolves_dependency_at_head_when_no_version_tags
+    metadata = {dependencies: {"missing": "*"}}
+    with_shard(metadata) { run "shards install" }
+    assert_installed "missing", "0.1.0"
+  end
+
   def test_installs_dependency_at_locked_commit_when_refs_is_a_branch
     metadata = {
       dependencies: {

test/integration_helper.cr

@@ -52,9 +52,13 @@ class Minitest::Test
     # path dependency:
     create_path_repository "foo", "0.1.0"
 
-    # dependency with neither a shard.yml nor version tags:
-    create_git_repository "empty"
-    create_git_commit "empty", "initial release"
+    # dependency with neither a shard.yml and/or version tags:
+    #create_git_repository "empty"
+    #create_git_commit "empty", "initial release"
+
+    create_git_repository "missing"
+    create_shard "missing", "name: missing\nversion: 0.1.0\n"
+    create_git_commit "missing", "initial release"
 
     # dependencies with postinstall scripts:
     create_git_repository "post"