Add configuration path explanations

internal/adapter/cli/config_test.go

@@ -126,3 +126,82 @@ func TestConfigCommandFailuresDoNotProduceSuccessfulOutput(t *testing.T) {
 		t.Fatalf("source writer error returned %d", code)
 	}
 }
+
+func TestConfigExplainUsesResolvedHistoryAndKeepsParametersVisible(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dir, "overlays"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	base := filepath.Join(dir, "config.yml")
+	for path, body := range map[string]string{
+		base: `prompt_dir: " ./prompts/../prompts "
+server:
+  addr: :8080
+backends:
+  "team/blue~1":
+    endpoint: http://127.0.0.1:1/v1
+    api_key_env: SCRIPTORIUM_EXPLAIN_KEY
+    extra_params:
+      "0": base-parameter
+`,
+		filepath.Join(dir, "overlays", "local.yml"): `server:
+  addr: :9090
+backends:
+  "team/blue~1":
+    extra_params:
+      "0": overlay-parameter
+`,
+	} {
+		if err := os.WriteFile(path, []byte(body), 0o600); err != nil {
+			t.Fatal(err)
+		}
+	}
+	const keyValue = "synthetic-key-bytes-must-not-appear"
+	t.Setenv("SCRIPTORIUM_EXPLAIN_KEY", keyValue)
+	args := []string{"--config", base, "--config-overlay", "local", "--addr", ":9090"}
+	for _, tc := range []struct {
+		pointer string
+		want    []string
+	}{
+		{pointer: "/server/addr", want: []string{":8080", ":9090", "--addr"}},
+		{pointer: "/prompt_dir", want: []string{"normalized application path", "prompts"}},
+		{pointer: "/backends/team~1blue~01/extra_params/0", want: []string{"base-parameter", "overlay-parameter"}},
+		{pointer: "/backends/team~1blue~01/api_key_env", want: []string{"SCRIPTORIUM_EXPLAIN_KEY"}},
+		{pointer: "", want: []string{"base-parameter", "overlay-parameter", "SCRIPTORIUM_EXPLAIN_KEY"}},
+	} {
+		code, stdout, stderr := runCLICommand(t, configCommand, append([]string{"explain", "--path", tc.pointer}, args...))
+		if code != ExitOK || stderr != "" || strings.Contains(stdout, keyValue) {
+			t.Fatalf("explain %q failed or disclosed key: code=%d out=%q err=%q", tc.pointer, code, stdout, stderr)
+		}
+		for _, want := range tc.want {
+			if !strings.Contains(stdout, want) {
+				t.Fatalf("explain %q lacks %q: %q", tc.pointer, want, stdout)
+			}
+		}
+	}
+	if err := os.Unsetenv("SCRIPTORIUM_EXPLAIN_KEY"); err != nil {
+		t.Fatal(err)
+	}
+	code, stdout, stderr := runCLICommand(t, configCommand, append([]string{"explain", "--path", "/backends/team~1blue~01/api_key_env"}, args...))
+	if code != ExitOK || stderr != "" || !strings.Contains(stdout, "SCRIPTORIUM_EXPLAIN_KEY") || strings.Contains(stdout, keyValue) {
+		t.Fatalf("absent credential changed reference explanation: code=%d out=%q err=%q", code, stdout, stderr)
+	}
+}
+
+func TestConfigExplainRejectsUnknownOrMalformedPaths(t *testing.T) {
+	path := writeAppConfigFile(t, "{}\n")
+	for _, args := range [][]string{
+		{"explain", "--config", path},
+		{"explain", "--config", path, "--path", "not-a-pointer"},
+		{"explain", "--config", path, "--path", "/missing"},
+	} {
+		code, stdout, stderr := runCLICommand(t, configCommand, args)
+		if code != ExitRuntimeError || stdout != "" || stderr == "" {
+			t.Fatalf("invalid explanation path accepted: args=%q code=%d out=%q err=%q", args, code, stdout, stderr)
+		}
+	}
+	var stderr bytes.Buffer
+	if code := configCommand([]string{"explain", "--config", path, "--path", ""}, errorOutputWriter{}, &stderr); code != ExitRuntimeError || !strings.Contains(stderr.String(), "output error") {
+		t.Fatalf("explanation writer failure not reported: code=%d err=%q", code, stderr.String())
+	}
+}