Keep output machine readable using `spack find --format` in an env (#19698)

Currently, full JSON output is the only machine readable option for `spack find`
in an environment.

`spack find --format` is also designed to be machine readable, but we print extra
headers in environments.

-[x] don't print headers in `spack find` output when in an environment

2 files changed, 4 insertions, 2 deletions

diff --git a/lib/spack/spack/cmd/find.py b/lib/spack/spack/cmd/find.py
index db229aca7e..d9d51b853c 100644
--- a/lib/spack/spack/cmd/find.py
+++ b/lib/spack/spack/cmd/find.py
@@ -235,8 +235,9 @@ def find(parser, args):
     if args.json:
         cmd.display_specs_as_json(results, deps=args.deps)
     else:
-        if env:
-            display_env(env, args, decorator)
+        if not args.format:
+            if env:
+                display_env(env, args, decorator)
         if sys.stdout.isatty() and args.groups:
             tty.msg("%s" % plural(len(results), 'installed package'))
         cmd.display_specs(
diff --git a/lib/spack/spack/test/cmd/find.py b/lib/spack/spack/test/cmd/find.py
index 8d3c68d31a..9d2203aaaf 100644
--- a/lib/spack/spack/test/cmd/find.py
+++ b/lib/spack/spack/test/cmd/find.py
@@ -209,6 +209,7 @@ def test_find_format(database, config):
 
     output = find('--format', '{name}-{version}-{compiler.name}-{^mpi.name}',
                   'mpileaks')
+    assert "installed package" not in output
     assert set(output.strip().split('\n')) == set([
         "mpileaks-2.3-gcc-zmpi",
         "mpileaks-2.3-gcc-mpich",