Show linked paths and per-release dependencies in --solve solutions

doc/user-changes.md

@@ -4,6 +4,20 @@ This document is a development diary summarizing changes in `alr` that notably
 affect the user experience. It is intended as a one-stop point for users to
 stay on top of `alr` new features.
 
+### Show release-specific dependency sets in solutions
+
+PR [#453](https://github.com/alire-project/alire/pull/453).
+
+The dependency solution shown with the `--solve` switch now details for each
+release the particular version set with which a dependency is brought into the
+dependency closure. For example:
+
+```
+Dependencies (graph):
+   hello=1.0.1      --> libhello=1.0.1 (^1.0)
+   superhello=1.0.0 --> libhello=1.0.1 (~1.0)
+```
+
 ### Use crate metadata when pinning to a directory
 
 PR [#450](https://github.com/alire-project/alire/pull/450).

src/alire/alire-dependencies-graphs.adb

@@ -2,6 +2,7 @@ with Alire.Conditional;
 with Alire.Directories;
 with Alire.OS_Lib.Subprocess;
 with Alire.Paths;
+with Alire.Root;
 with Alire.Utils.Tables;
 
 package body Alire.Dependencies.Graphs is
@@ -87,21 +88,51 @@ package body Alire.Dependencies.Graphs is
    -- Label --
    -----------
 
-   function Label (Crate    : Crate_Name;
-                   Solution : Solutions.Solution;
-                   TTY      : Boolean := False)
-                   return String
+   function Label_Dependee (Dependent : Crate_Name;
+                            Dependee  : Crate_Name;
+                            Solution  : Solutions.Solution;
+                            For_Plot  : Boolean)
+                            return String
    --  Get the proper label in the graph for a crate: milestone for releases,
    --  dependency for hints.
-   is (if Solution.Releases.Contains (Crate)
-       then (if TTY
-             then Solution.Releases.Element (Crate).Milestone.TTY_Image
-             else Solution.Releases.Element (Crate).Milestone.Image)
-       elsif Solution.Depends_On (Crate)
-       then (if TTY
-             then Solution.Dependency (Crate).TTY_Image
-             else Solution.Dependency (Crate).Image)
-       else raise Program_Error with "crate should appear as release or hint");
+   is
+   begin
+
+      --  For a solved dependency, return "crate=version (original dependency)"
+      --  For an unsolved dependency, return "crate^dependency". In the case of
+      --  For_Plot, omit the (original dependency).
+
+      if Solution.State (Dependee).Has_Release then
+         if For_Plot then
+            return Solution.State (Dependee).Release.Milestone.Image;
+         else
+            return Solution.State (Dependee).Release.Milestone.TTY_Image
+              & " ("
+              & TTY.Version
+               (Solution.Dependency (Dependent, Dependee).Versions.Image)
+              & ")";
+         end if;
+      else
+         if For_Plot then
+            return Solution.Dependency (Dependent, Dependee).Image;
+         else
+            return Solution.Dependency (Dependent, Dependee).TTY_Image;
+         end if;
+      end if;
+   end Label_Dependee;
+
+   ---------------------
+   -- Label_Dependent --
+   ---------------------
+
+   function Label_Dependent (Crate    : Crate_Name;
+                             Solution : Solutions.Solution;
+                             TTY      : Boolean := False)
+                             return String
+   is (if TTY then
+          Solution.State (Crate).Release.Milestone.TTY_Image
+       else
+          Solution.State (Crate).Release.Milestone.Image);
 
    ----------
    -- Plot --
@@ -121,13 +152,19 @@ package body Alire.Dependencies.Graphs is
       Alt.Append ("graph dependencies {");
 
       for Dep of Filtered loop
-         Alt.Append (Q (Label (+Dep.Dependent, Solution)) &
-                          " -> " &
-                          Q (Label (+Dep.Dependee, Solution)) & "; ");
-
-         Source.Append (B (Label (+Dep.Dependent, Solution)) &
-                          " -> " &
-                          B (Label (+Dep.Dependee, Solution)));
+         Alt.Append (Q (Label_Dependent (+Dep.Dependent, Solution))
+                     & " -> "
+                     & Q (Label_Dependee (+Dep.Dependent,
+                                          +Dep.Dependee,
+                                          Solution,
+                                          For_Plot => True)) & "; ");
+
+         Source.Append (B (Label_Dependent (+Dep.Dependent, Solution))
+                        & " -> "
+                        & B (Label_Dependee (+Dep.Dependent,
+                                             +Dep.Dependee,
+                                             Solution,
+                                             For_Plot => True)));
       end loop;
       Alt.Append (" }");
 
@@ -154,9 +191,12 @@ package body Alire.Dependencies.Graphs is
       Filtered : constant Graph := This.Filtering_Unused (Solution.Crates);
    begin
       for Dep of Filtered loop
-         Table.Append (Prefix & Label (+Dep.Dependent, Solution, TTY => True));
+         Table.Append
+           (Prefix & Label_Dependent (+Dep.Dependent, Solution, TTY => True));
          Table.Append ("-->");
-         Table.Append (Label (+Dep.Dependee, Solution, TTY => True));
+         Table.Append
+           (Label_Dependee
+              (+Dep.Dependent, +Dep.Dependee, Solution, For_Plot => False));
          Table.New_Row;
       end loop;
 

src/alire/alire-solutions.adb

@@ -5,6 +5,7 @@ with Alire.Dependencies.Graphs;
 with Alire.Index;
 with Alire.OS_Lib.Subprocess;
 with Alire.Paths;
+with Alire.Root;
 with Alire.Solutions.Diffs;
 with Alire.Utils.Tables;
 with Alire.Utils.TTY;
@@ -37,6 +38,33 @@ package body Alire.Solutions is
       end return;
    end Dependencies_That;
 
+   ----------------
+   -- Dependency --
+   ----------------
+
+   function Dependency (This      : Solution;
+                        Dependent : Crate_Name;
+                        Dependee  : Crate_Name)
+                        return Dependencies.Dependency
+   is
+   begin
+      --  This is not particularly efficient. An Enumerate version that
+      --  returned a map would serve better here if this proves to be a
+      --  bottleneck in the future.
+
+      for Dep of
+        Conditional.Enumerate
+          (This.State (Dependent)
+               .Release.Dependencies (Root.Platform_Properties))
+      loop
+         if Dep.Crate = Dependee then
+            return Dep;
+         end if;
+      end loop;
+
+      raise Program_Error with "invalid dependency request (body)";
+   end Dependency;
+
    -------------
    -- Changes --
    -------------
@@ -331,26 +359,31 @@ package body Alire.Solutions is
 
       if not This.Releases.Is_Empty then
          Trace.Log ("Dependencies (solution):", Level);
+
          for Rel of This.Releases loop
             Trace.Log ("   " & Rel.Milestone.TTY_Image
-                       & (if This.State (Rel.Name).Is_Pinned
+                       & (if This.State (Rel.Name).Is_Pinned or else
+                             This.State (Rel.Name).Is_Linked
                          then TTY.Emph (" (pinned)")
                          else "")
-                       & (if Detailed then
-                            " (origin: " &
-                            Utils.To_Lower_Case (Rel.Origin.Kind'Img) & ")"
-                         else
-                            ""),
+                       & (if Detailed
+                         then " (origin: "
+                             & (if This.State (Rel.Name).Is_Linked
+                                then TTY.URL (This.State (Rel.Name).Link.Path)
+                                else Utils.To_Lower_Case (Rel.Origin.Kind'Img))
+                             & ")"
+                         else ""),
                        Level);
          end loop;
       end if;
 
       --  Show other dependencies with their status and hints
 
-      if (for some Dep of This.Dependencies => not Dep.Is_Solved) then
+      if (for some Dep of This.Dependencies => not Dep.Has_Release) then
          Trace.Log ("Dependencies (external):", Level);
          for Dep of This.Dependencies loop
-            if not This.State (Dep.Crate).Is_Solved then
+            if not This.State (Dep.Crate).Has_Release
+            then
                Trace.Log ("   " & Dep.TTY_Image, Level);
 
                --  Look for hints. If we are relying on workspace information

src/alire/alire-solutions.ads

@@ -184,6 +184,17 @@ package Alire.Solutions is
      with Pre => This.Depends_On (Crate);
    --  Return the specific dependency versions as currently stored
 
+   function Dependency (This      : Solution;
+                        Dependent : Crate_Name;
+                        Dependee  : Crate_Name)
+                        return Dependencies.Dependency
+     with Pre =>
+       (This.State (Dependent).Has_Release and then This.Depends_On (Dependee))
+       or else raise Program_Error with "invalid dependency request";
+   --  The solver groups dependencies on a same crate by several dependents.
+   --  This function allows identifying the concrete dependency that a solved
+   --  release introduced in the solution.
+
    function Depends_On (This : Solution;
                         Name : Crate_Name) return Boolean;
    --  Says if the solution depends on the crate in some way

testsuite/fixtures/solver_index/su/superhello.toml

@@ -0,0 +1,14 @@
+[general]
+description = "A better hello"
+licenses = ["GPL 3.0", "MIT"]
+website = "example.com"
+maintainers = ["bob@example.com"]
+maintainers-logins = ["mylogin"]
+authors = ["Bob", "Alice"]
+
+
+['1.0.0']
+origin = "file://."
+
+    ['1.0.0'.depends-on]
+    libhello = "~1.0"

testsuite/tests/solver/one-dep-two-constraints/test.py

@@ -0,0 +1,35 @@
+"""
+Test that a dependency that is introduced by two dependents with different
+constraints is properly solved and shown.
+"""
+
+import os
+import re
+
+from drivers.alr import run_alr
+from drivers.asserts import assert_match
+
+# Initialize project
+run_alr('init', '--bin', 'xxx')
+os.chdir('xxx')
+
+# Add dependency on hello^1. Solution is hello=1.0.1 --> libhello=1.1.0
+run_alr('with', 'hello^1')
+p = run_alr('with', '--solve')
+assert_match('.*'  # skip solution
+             'Dependencies \(graph\):\n'
+             '   hello=1.0.1 --> libhello=1.1.0 \(\^1.0\).*',
+             p.out, flags=re.S)
+
+# Add dependency on superhello*. Solution is superhello=1.0 --> libhello=1.0.1
+# This implies a downgrade from libhello=1.1.0 to libhello=1.0.1, which is the
+# only possible combination of libhello^1.0 & libhello~1.0
+run_alr('with', 'superhello')
+p = run_alr('with', '--solve')
+assert_match('.*'  # skip solution
+             'Dependencies \(graph\):\n'
+             '   hello=1.0.1      --> libhello=1.0.1 \(\^1.0\)\n'
+             '   superhello=1.0.0 --> libhello=1.0.1 \(~1.0\).*',
+             p.out, flags=re.S)
+
+print('SUCCESS')

testsuite/tests/solver/one-dep-two-constraints/test.yaml

@@ -0,0 +1,3 @@
+driver: python-script
+indexes:
+    solver_index: {}