Move ASCII graph to --graph switch, and add a --tree alternative …

…& fallback (#465)

* New `alr with --tree`, `alr show --tree` switch

Prints dependency graph in tree form, as an alternative to the ascii-art plots
that 1) not always will be available, depending in libgraph-easy-perl and 2)
quickly become big and broken.

* Move ASCII graph to dedicated --graph switch

Previously, it was always attempted to be shown with `--solve`, which could be
an unnecessary pollution for an otherwise useful command.

* Update user-changes document

doc/user-changes.md

@@ -4,6 +4,25 @@ 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.
 
+### New `alr with --graph` and `alr with --tree` switches
+
+PR [#465](https://github.com/alire-project/alire/pull/465).
+
+The ASCII art dependency graph generated with `graph-easy`, that was printed at
+the end of `alr with --solve` output, is moved to its own `alr with --graph`
+switch. A fallback tree visualization is generated when `graph-easy` is
+unavailable. This new tree visualization can also be obtained with `alr with
+--tree`:
+```
+my_project=0.0.0
+├── hello=1.0.1 (^1)
+│   └── libhello=1.0.1 (^1.0)
+├── superhello=1.0.0 (*)
+│   └── libhello=1.0.1 (~1.0)
+├── unobtanium* (direct,missed) (*)
+└── wip* (direct,linked,pin=/fake) (*)
+```
+
 ### Automatically 'with' GPR project files from dependencies
 
 PR [#458](https://github.com/alire-project/alire/pull/458).

src/alire/alire-solutions.adb

@@ -1,13 +1,13 @@
 with Ada.Containers;
 
 with Alire.Crates.With_Releases;
+with Alire.Dependencies.Containers;
 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.Tools;
 with Alire.Utils.TTY;
 
 with Semantic_Versioning;
@@ -283,14 +283,6 @@ package body Alire.Solutions is
       end case;
    end Is_Better;
 
-   ----------------------------------
-   -- Libgraph_Easy_Perl_Installed --
-   ----------------------------------
-
-   function Libgraph_Easy_Perl_Installed return Boolean
-   is (OS_Lib.Subprocess.Locate_In_Path (Paths.Scripts_Graph_Easy) /= "");
-   --  Return whether libgraph_easy_perl_install is in path
-
    ------------------
    -- New_Solution --
    ------------------
@@ -425,21 +417,41 @@ package body Alire.Solutions is
                         .From_Solution (With_Root, Env);
          begin
             Graph.Print (With_Root, Prefix => "   ");
+         end;
+      end if;
+   end Print;
 
-            --  Optional graphical if possible. TODO: remove this warning once
-            --  show once.
+   -----------------
+   -- Print_Graph --
+   -----------------
 
-            if Libgraph_Easy_Perl_Installed then
+   procedure Print_Graph (This     : Solution;
+                          Root     : Alire.Releases.Release;
+                          Env      : Properties.Vector)
+   is
+   begin
+      if This.Dependencies.Is_Empty then
+         Trace.Always ("There are no dependencies.");
+      else
+         Utils.Tools.Check_Tool (Utils.Tools.Easy_Graph, Fail => False);
+
+         if Utils.Tools.Available (Utils.Tools.Easy_Graph) then
+            declare
+               With_Root : constant Solution :=
+                             This.Including
+                               (Root, Env, Add_Dependency => True);
+               Graph     : constant Alire.Dependencies.Graphs.Graph :=
+                             Alire.Dependencies.Graphs
+                               .From_Solution (With_Root, Env);
+            begin
                Graph.Plot (With_Root);
-            else
-               Trace.Log ("Cannot display graphical graph: " &
-                            Paths.Scripts_Graph_Easy & " not in path" &
-                            " (usually packaged as libgraph_easy_perl).",
-                          Level);
-            end if;
-         end;
+            end;
+         else
+            Trace.Info ("Defaulting to tree view.");
+            This.Print_Tree (Root);
+         end if;
       end if;
-   end Print;
+   end Print_Graph;
 
    -----------------
    -- Print_Hints --
@@ -497,6 +509,97 @@ package body Alire.Solutions is
       end if;
    end Print_Pins;
 
+   ----------------
+   -- Print_Tree --
+   ----------------
+
+   procedure Print_Tree (This       : Solution;
+                         Root       : Alire.Releases.Release;
+                         Prefix     : String := "";
+                         Print_Root : Boolean := True)
+   is
+
+      Mid_Node  : constant String :=
+                    (if TTY.Color_Enabled then "├── " else "+-- ");
+      Last_Node : constant String :=
+                    (if TTY.Color_Enabled then "└── " else "+-- ");
+      Branch    : constant String :=
+                    (if TTY.Color_Enabled then "│   " else "|   ");
+      No_Branch : constant String := "    ";
+
+      procedure Print (Deps   : Dependencies.Containers.List;
+                       Prefix : String := "";
+                       Omit   : Boolean := False)
+        --  Omit is used to remove the top-level connectors, for when the tree
+        --  is printed without the root release.
+      is
+         Last : UString;
+         --  Used to store the last dependency name in a subtree, to be able to
+         --  use the proper ASCII connector. See just below.
+      begin
+
+         --  Find last printable dependency. This is related to OR trees, that
+         --  might cause the last in the enumeration to not really belong to
+         --  the solution.
+
+         for Dep of Deps loop
+            if This.Depends_On (Dep.Crate) then
+               Last := +(+Dep.Crate);
+            end if;
+         end loop;
+
+         --  Print each dependency for real
+
+         for Dep of Deps loop
+            if This.Depends_On (Dep.Crate) then
+               Trace.Always
+                 (Prefix
+                  --  The prefix is the possible "|" connectors from upper tree
+                  --  levels.
+
+                  --  Print the appropriate final connector for the node
+                  & (if Omit -- top-level, no prefix
+                    then ""
+                    else (if +Dep.Crate = +Last
+                          then Last_Node  -- A └── connector
+                          else Mid_Node)) -- A ├── connector
+
+                  --  For a dependency solved by a release, print exact
+                  --  version. Otherwise print the state of the dependency.
+                  & (if This.State (Dep.Crate).Has_Release
+                    then This.State (Dep.Crate).Release.Milestone.TTY_Image
+                    else This.State (Dep.Crate).TTY_Image)
+
+                  --  And dependency that introduces the crate in the solution
+                  & " (" & TTY.Emph (Dep.Versions.Image) & ")");
+
+               --  Recurse for further releases
+
+               if This.State (Dep.Crate).Has_Release then
+                  Print (Conditional.Enumerate
+                           (This.State (Dep.Crate).Release.Dependencies),
+                         Prefix =>
+                           Prefix
+                           --  Indent adding the proper running connector
+                           & (if Omit
+                              then ""
+                              else (if +Dep.Crate = +Last
+                                    then No_Branch  -- End of this connector
+                                    else Branch))); -- "│" over the subtree
+               end if;
+            end if;
+         end loop;
+      end Print;
+
+   begin
+      if Print_Root then
+         Trace.Always (Prefix & Root.Milestone.TTY_Image);
+      end if;
+      Print (Conditional.Enumerate (Root.Dependencies),
+             Prefix,
+             not Print_Root);
+   end Print_Tree;
+
    --------------
    -- Releases --
    --------------

src/alire/alire-solutions.ads

@@ -270,13 +270,26 @@ package Alire.Solutions is
    --  crate not in solution that introduces the direct dependencies. When
    --  Detailed, extra information about origins is shown.
 
+   procedure Print_Graph (This     : Solution;
+                          Root     : Alire.Releases.Release;
+                          Env      : Properties.Vector);
+   --  Print an ASCII graph of dependencies using libgraph-easy-perl, if
+   --  installed, or default to Print_Tree.
+
    procedure Print_Hints (This : Solution;
                           Env  : Properties.Vector);
    --  Display hints about any undetected externals in the solutions
 
    procedure Print_Pins (This : Solution);
    --  Dump a table with pins in this solution
 
+   procedure Print_Tree (This       : Solution;
+                         Root       : Alire.Releases.Release;
+                         Prefix     : String := "";
+                         Print_Root : Boolean := True);
+   --  Print the solution in tree form. If Print_Root, Root is printed too;
+   --  otherwise the tree is a forest starting at Root direct dependencies.
+
    -----------------
    -- Persistence --
    -----------------

src/alire/alire-utils-tools.adb

@@ -9,12 +9,33 @@ package body Alire.Utils.Tools is
 
    Already_Detected : array (Tool_Kind) of Boolean := (others => False);
 
+   function Exec_For_Tool (Tool : Tool_Kind) return String;
+
+   ---------------
+   -- Available --
+   ---------------
+
+   function Available (Tool : Tool_Kind) return Boolean is
+   begin
+      if Already_Detected (Tool) then
+         return True;
+      end if;
+
+      if Locate_In_Path (Exec_For_Tool (Tool)) /= "" then
+         --  The tool is available
+         Already_Detected (Tool) := True;
+      end if;
+
+      return Already_Detected (Tool);
+   end Available;
+
    -------------------
    -- Exec_For_Tool --
    -------------------
 
    function Exec_For_Tool (Tool : Tool_Kind) return String
    is (case Tool is
+          when Easy_Graph => "graph-easy",
           when Git        => "git",
           when Tar        => "tar",
           when Unzip      => "unzip",
@@ -38,8 +59,12 @@ package body Alire.Utils.Tools is
 
          when Msys2 | Debian | Ubuntu =>
             return (case Tool is
+                       when Easy_Graph =>
+                         (if Distribution /= Msys2
+                          then "libgraph-easy-perl"
+                          else ""),
                        when Git | Tar | Unzip | Curl => Exec_For_Tool (Tool),
-                       when Mercurial => "mercurial",
+                       when Mercurial  => "mercurial",
                        when Subversion => "subversion");
       end case;
    end System_Package_For_Tool;
@@ -48,7 +73,7 @@ package body Alire.Utils.Tools is
    -- Install_From_Distrib --
    --------------------------
 
-   procedure Install_From_Distrib (Tool : Tool_Kind) is
+   procedure Install_From_Distrib (Tool : Tool_Kind; Fail : Boolean) is
       use Utils.User_Input;
 
       Pck : constant String := System_Package_For_Tool (Tool);
@@ -87,16 +112,27 @@ package body Alire.Utils.Tools is
             end;
          else
             --  Error when user rejected installation
-            Trace.Error ("Cannot proceed.");
-            Trace.Error ("Please install the tool and retry.");
+            if Fail then
+               Trace.Error ("Cannot proceed.");
+               Trace.Error ("Please install the tool and retry.");
+            else
+               Trace.Info ("Tool not installed.");
+               return;
+            end if;
          end if;
       else
          --  Error when Alire doesn't know how to install (unknown distro or
          --  tool not available in distro).
-         Trace.Error ("Cannot proceed.");
-         Trace.Error ("Alire is not able to install required tool: '" &
-                        Tool'Img & "'");
-         Trace.Error ("Please install the tool and retry.");
+         if Fail then
+            Trace.Error ("Cannot proceed.");
+            Trace.Error ("Alire is not able to install required tool: '" &
+                           Tool'Img & "'");
+            Trace.Error ("Please install the tool and retry.");
+         else
+            Trace.Warning ("Alire is not able to install tool: '" &
+                             Tool'Img & "'");
+            return;
+         end if;
       end if;
 
       OS_Lib.Bailout (1);
@@ -106,22 +142,16 @@ package body Alire.Utils.Tools is
    -- Check_Tool --
    ----------------
 
-   procedure Check_Tool (Tool : Tool_Kind) is
+   procedure Check_Tool (Tool : Tool_Kind; Fail : Boolean := True) is
    begin
 
-      if Already_Detected (Tool) then
-         return;
-      end if;
-
-      if Locate_In_Path (Exec_For_Tool (Tool)) /= "" then
-         --  The tool is available
-         Already_Detected (Tool) := True;
+      if Available (Tool) then
          return;
       end if;
 
       Trace.Info ("Cannot find required tool: " & Tool'Img);
 
-      Install_From_Distrib (Tool);
+      Install_From_Distrib (Tool, Fail);
    end Check_Tool;
 
 end Alire.Utils.Tools;

src/alire/alire-utils-tools.ads

@@ -1,9 +1,14 @@
 package Alire.Utils.Tools is
 
-   type Tool_Kind is (Git, Tar, Unzip, Curl, Mercurial, Subversion);
+   type Tool_Kind is
+     (Easy_Graph, Git, Tar, Unzip, Curl, Mercurial, Subversion);
 
-   procedure Check_Tool (Tool : Tool_Kind);
+   function Available (Tool : Tool_Kind) return Boolean;
+   --  Say if tool is already available (attemps detection for the tool, but
+   --  does not install it if missing).
+
+   procedure Check_Tool (Tool : Tool_Kind; Fail : Boolean := True);
    --  Check if a required executable tool is available in PATH.
-   --  If not, try to install it or abort.
+   --  If not, try to install it. If unable and Fail, abort, otherwise return
 
 end Alire.Utils.Tools;