fix: ability to pin a crate that 'provides' a dependency

src/alire/alire-dependencies-states.adb

@@ -52,7 +52,18 @@ package body Alire.Dependencies.States is
    begin
       if Opt_Root.Is_Valid then
          if Opt_Root.Value.Release.Name = Crate then
+
+            --  Simple case in which the release corresponds with the crate
             return To_Holder (Opt_Root.Value.Release);
+
+         elsif Opt_Root.Value.Release.Provides (Crate) then
+
+            --  But also, the release may be providing the crate instead
+            Trace.Debug ("Created optional release "
+                         & Opt_Root.Value.Release.Milestone.Image
+                         & " providing crate " & Crate.As_String);
+            return To_Holder (Opt_Root.Value.Release);
+
          else
             Raise_Checked_Error ("crate mismatch: expected "
                                  & Crate.TTY_Image

src/alire/alire-roots.adb

@@ -104,7 +104,7 @@ package body Alire.Roots is
    end Build_Prepare;
 
    -----------
-   -- Build --
+   -- noteBuild --
    -----------
 
    function Build (This             : in out Root;
@@ -1060,7 +1060,9 @@ package body Alire.Roots is
                if Target.Is_Valid then
                   Trace.Debug
                     ("Crate found at pin location " & Pin.Relative_Path);
-                  if Target.Value.Name /= Crate then
+                  if Target.Value.Name /= Crate and then
+                    not Target.Value.Release.Element.Provides (Crate)
+                  then
                      Raise_Checked_Error
                        ("Mismatched crates for pin linking to "
                         & TTY.URL (Pin.Path) & ": expected " &

testsuite/tests/pin/crate-with-provides/test.py

@@ -0,0 +1,40 @@
+"""
+Verify that we can link-pin a crate that has "provides" in a variety of ways.
+"""
+
+import os
+from drivers.alr import run_alr, init_local_crate, alr_manifest
+from drivers.asserts import assert_eq, assert_match, match_solution
+
+# Create the target crate
+init_local_crate(name="mylib")
+# Update its manifest
+with open(alr_manifest(), "a") as f:
+    f.write('provides=["coollib=1.0.0"]')
+os.chdir("..")
+
+tests = [
+    ["with", "--use=../mylib"],
+    ["with", "coollib", "--use=../mylib"],
+]
+
+matches = [
+    "mylib=0.1.0-dev (pinned) (origin: ../mylib)",
+    "coollib=0.1.0-dev (mylib) (pinned) (origin: ../mylib)"
+]
+
+for target, test, id in zip(matches, tests, range(len(tests))):
+    # Create a new dependent crate
+    init_local_crate(f"myapp{id}")
+    run_alr(*test)
+    match_solution(target, escape=True)
+    os.chdir("..")
+
+# For the final test we need an extra step to force-add the dependency before
+# pinning.
+init_local_crate("myapp_final")
+run_alr("--force", "with", "coollib")  # Force because not in index
+run_alr("pin", "coollib", "--use=../mylib")
+match_solution(matches[-1], escape=True)
+
+print("SUCCESS")

testsuite/tests/pin/crate-with-provides/test.yaml

@@ -0,0 +1,4 @@
+driver: python-script
+build_mode: both
+indexes:
+    compiler_only_index: {}