spack spec: remove noisy @= from output (#37663)

@= is accurate, but noisy. Other UI commands tend not to
print the redundant `@=` for known concrete versions;
make `spack spec` consistent with them.

lib/spack/spack/cmd/solve.py

@@ -140,12 +140,15 @@ def _process_result(result, show, required_format, kwargs):
 
 def solve(parser, args):
     # these are the same options as `spack spec`
-    name_fmt = "{namespace}.{name}" if args.namespaces else "{name}"
-    fmt = "{@versions}{%compiler}{compiler_flags}{variants}{arch=architecture}"
     install_status_fn = spack.spec.Spec.install_status
+
+    fmt = spack.spec.display_format
+    if args.namespaces:
+        fmt = "{namespace}." + fmt
+
     kwargs = {
         "cover": args.cover,
-        "format": name_fmt + fmt,
+        "format": fmt,
         "hashlen": None if args.very_long else 7,
         "show_types": args.types,
         "status_fn": install_status_fn if args.install_status else None,

lib/spack/spack/cmd/spec.py

@@ -80,12 +80,15 @@ def setup_parser(subparser):
 
 
 def spec(parser, args):
-    name_fmt = "{namespace}.{name}" if args.namespaces else "{name}"
-    fmt = "{@versions}{%compiler}{compiler_flags}{variants}{arch=architecture}"
     install_status_fn = spack.spec.Spec.install_status
+
+    fmt = spack.spec.display_format
+    if args.namespaces:
+        fmt = "{namespace}." + fmt
+
     tree_kwargs = {
         "cover": args.cover,
-        "format": name_fmt + fmt,
+        "format": fmt,
         "hashlen": None if args.very_long else 7,
         "show_types": args.types,
         "status_fn": install_status_fn if args.install_status else None,

lib/spack/spack/environment/environment.py

@@ -2324,6 +2324,7 @@ def display_specs(concretized_specs):
     def _tree_to_display(spec):
         return spec.tree(
             recurse_dependencies=True,
+            format=spack.spec.display_format,
             status_fn=spack.spec.Spec.install_status,
             hashlen=7,
             hashes=True,

lib/spack/spack/spec.py

@@ -144,9 +144,20 @@
 #: ``color_formats.keys()``.
 _separators = "[\\%s]" % "\\".join(color_formats.keys())
 
-default_format = "{name}{@versions}"
-default_format += "{%compiler.name}{@compiler.versions}{compiler_flags}"
-default_format += "{variants}{arch=architecture}{/abstract_hash}"
+#: Default format for Spec.format(). This format can be round-tripped, so that:
+#:     Spec(Spec("string").format()) == Spec("string)"
+default_format = (
+    "{name}{@versions}"
+    "{%compiler.name}{@compiler.versions}{compiler_flags}"
+    "{variants}{arch=architecture}{/abstract_hash}"
+)
+
+#: Display format, which eliminates extra `@=` in the output, for readability.
+display_format = (
+    "{name}{@version}"
+    "{%compiler.name}{@compiler.version}{compiler_flags}"
+    "{variants}{arch=architecture}{/abstract_hash}"
+)
 
 #: Regular expression to pull spec contents out of clearsigned signature
 #: file.

lib/spack/spack/test/cmd/spec.py

@@ -24,12 +24,12 @@
 def test_spec():
     output = spec("mpileaks")
 
-    assert "mpileaks@=2.3" in output
-    assert "callpath@=1.0" in output
-    assert "dyninst@=8.2" in output
-    assert "libdwarf@=20130729" in output
-    assert "libelf@=0.8.1" in output
-    assert "mpich@=3.0.4" in output
+    assert "mpileaks@2.3" in output
+    assert "callpath@1.0" in output
+    assert "dyninst@8.2" in output
+    assert "libdwarf@20130729" in output
+    assert "libelf@0.8.1" in output
+    assert "mpich@3.0.4" in output
 
 
 def test_spec_concretizer_args(mutable_config, mutable_database):
@@ -197,12 +197,12 @@ def test_env_aware_spec(mutable_mock_env_path):
 
     with env:
         output = spec()
-        assert "mpileaks@=2.3" in output
-        assert "callpath@=1.0" in output
-        assert "dyninst@=8.2" in output
-        assert "libdwarf@=20130729" in output
-        assert "libelf@=0.8.1" in output
-        assert "mpich@=3.0.4" in output
+        assert "mpileaks@2.3" in output
+        assert "callpath@1.0" in output
+        assert "dyninst@8.2" in output
+        assert "libdwarf@20130729" in output
+        assert "libelf@0.8.1" in output
+        assert "mpich@3.0.4" in output
 
 
 @pytest.mark.parametrize(