The output order for `spack diff` is nondeterministic for larger diffs -- if you
ran it several times it will not put the fields in the spec in the same order on
successive invocations.
This makes a few fixes to `spack diff`:
- [x] Implement the change discussed in https://github.com/spack/spack/pull/22283#discussion_r598337448
to make `AspFunction` comparable in and of itself and to eliminate the need for `to_tuple()`
- [x] Sort the lists of diff properties so that the output is always in the same order.
- [x] Make the output for different fields the same as what we use in the solver. Previously, we
would use `Type(value)` for non-string values and `value` for strings. Now we just use
the value. So the output looks a little cleaner:
```
== Old ========================== == New ====================
@@ node_target @@ @@ node_target @@
- gdbm Target(x86_64) - gdbm x86_64
+ zlib Target(skylake) + zlib skylake
@@ variant_value @@ @@ variant_value @@
- ncurses symlinks bool(False) - ncurses symlinks False
+ zlib optimize bool(True) + zlib optimize True
@@ version @@ @@ version @@
- gdbm Version(1.18.1) - gdbm 1.18.1
+ zlib Version(1.2.11) + zlib 1.2.11
@@ node_os @@ @@ node_os @@
- gdbm catalina - gdbm catalina
+ zlib catalina + zlib catalina
```
I suppose if we want to use `repr()` in the output we could do that and could be
consistent but we don't do that elsewhere -- the types of things in Specs are
all stringifiable so the string and the name of the attribute (`version`, `node_os`,
etc.) are sufficient to know what they are.
ab5954520f