Fix alias_dsn detection for --list-dsn and -D

changelog.rst

@@ -24,6 +24,12 @@ Internal:
 
 Bug fixes:
 ----------
+* Fix ``--list-dsn`` and ``-D``/``--dsn`` not finding ``[alias_dsn]`` entries.
+  On a fresh install (no config written yet) ``--list-dsn`` printed a misleading
+  "Invalid DSNs found" error. ``--list-dsn`` now treats a missing config or
+  ``[alias_dsn]`` section as simply nothing to list, without writing a config
+  file, and ``-D`` resolves the alias from the config already loaded at startup
+  instead of reading it again ([issue 1489](https://github.com/dbcli/pgcli/issues/1489)).
 * Restore cursor shape behaviour for Emacs mode
 * Fix ``TypeError: cannot use a string pattern on a bytes-like object`` when
   completion metadata comes back as bytes (e.g. ``SQL_ASCII`` client encoding).

pgcli/main.py

@@ -1632,9 +1632,14 @@ def cli(
                 config_full_path,
             )
     if list_dsn:
+        config_file = get_config_filename(pgclirc)
+        if not os.path.exists(config_file):
+            # Nothing is configured yet, so there is nothing to list. Don't write
+            # out the default config just to read it back for a read-only command.
+            sys.exit(0)
         try:
-            cfg = load_config(pgclirc, config_full_path)
-            for alias in cfg["alias_dsn"]:
+            cfg = load_config(config_file)
+            for alias in cfg.get("alias_dsn", {}):
                 click.secho(alias + " : " + cfg["alias_dsn"][alias])
             sys.exit(0)
         except Exception:
@@ -1686,7 +1691,9 @@ def cli(
     if list_databases or ping_database:
         database = "postgres"
 
-    cfg = load_config(pgclirc, config_full_path)
+    # PGCli() already loaded (and, if needed, wrote) the config above, so reuse it
+    # rather than reading the file a second time to resolve the -D alias.
+    cfg = pgcli.config
     if dsn != "":
         try:
             dsn_config = cfg["alias_dsn"][dsn]

tests/test_alias_dsn.py

@@ -0,0 +1,90 @@
+import pytest
+from click.testing import CliRunner
+
+from pgcli.main import cli, PGCli
+
+
+def write_config(tmp_path, body):
+    cfg = tmp_path / "config"
+    cfg.write_text(body)
+    return cfg
+
+
+@pytest.fixture
+def isolate_config(monkeypatch, tmp_path):
+    # Keep the real config dir out of the picture. get_config() writes its
+    # default template under here when a config file does not exist yet.
+    monkeypatch.setenv("XDG_CONFIG_HOME", str(tmp_path))
+    return tmp_path
+
+
+def test_list_dsn_fresh_config(isolate_config):
+    # No config file exists yet. --list-dsn used to read the not-yet-written
+    # config before PGCli() created it, hit a KeyError on the missing
+    # [alias_dsn] section, and print "Invalid DSNs found" with exit code 1.
+    # It should just report no aliases and exit cleanly.
+    cfg = isolate_config / "config"
+    runner = CliRunner()
+    result = runner.invoke(cli, ["--pgclirc", str(cfg), "--list-dsn"])
+    assert result.exit_code == 0
+    assert "Invalid DSNs" not in result.output
+    assert result.output.strip() == ""
+    # A read-only command must not create the config file as a side effect.
+    assert not cfg.exists()
+
+
+def test_list_dsn_lists_aliases(isolate_config):
+    cfg = write_config(
+        isolate_config,
+        "[alias_dsn]\nfoo = postgres://u:p@localhost:5432/foo\nbar = postgres://u:p@localhost:5432/bar\n",
+    )
+    runner = CliRunner()
+    result = runner.invoke(cli, ["--pgclirc", str(cfg), "--list-dsn"])
+    assert result.exit_code == 0
+    assert "foo : postgres://u:p@localhost:5432/foo" in result.output
+    assert "bar : postgres://u:p@localhost:5432/bar" in result.output
+
+
+def test_dsn_alias_resolves(isolate_config, monkeypatch):
+    cfg = write_config(
+        isolate_config,
+        "[alias_dsn]\nfoo = postgres://u:p@localhost:5432/foo\n",
+    )
+    captured = {}
+
+    def fake_connect(self, *args, **kwargs):
+        # connect_uri() parses the alias URI and calls connect() with the
+        # resolved parts, so recording them proves the alias was found.
+        captured.update(kwargs)
+
+        class DummyExec:
+            def run(self, cmd):
+                return []
+
+            def get_timezone(self):
+                return "UTC"
+
+            def set_timezone(self, *a, **k):
+                pass
+
+        self.pgexecute = DummyExec()
+
+    monkeypatch.setattr(PGCli, "connect", fake_connect)
+
+    runner = CliRunner()
+    result = runner.invoke(cli, ["--pgclirc", str(cfg), "-D", "foo", "--ping"])
+    assert result.exit_code == 0
+    assert "Could not find a DSN" not in result.output
+    assert captured.get("database") == "foo"
+    assert captured.get("host") == "localhost"
+
+
+def test_dsn_alias_missing(isolate_config):
+    cfg = write_config(
+        isolate_config,
+        "[alias_dsn]\nfoo = postgres://u:p@localhost:5432/foo\n",
+    )
+    runner = CliRunner()
+    result = runner.invoke(cli, ["--pgclirc", str(cfg), "-D", "does-not-exist"])
+    assert result.exit_code == 1
+    assert "Could not find a DSN with alias does-not-exist" in result.output