cli: add 'show operational [path /X]' and path filter to config views

Extend the existing 'show <running|startup|factory>-config' family with an
optional 'path /XPATH' argument that maps straight to the underlying 'copy
-x' flag, and add 'show operational [path /XPATH]' for symmetry with the
configuration datastores.

  admin@example:/> show running-config path /ietf-interfaces:interfaces
  admin@example:/> show operational path /ietf-system:system-state

Also, improve error feedback from the copy command slightly.

Before:
  admin@example:~$ copy running -x /foo
  Error: (null) (5)
  Error: failed retrieving running-config data

After:
  admin@example:~$ copy running -x /foo
  Error: Couldn't parse path "/foo": Prefix "foo" not defined. (5)
  Error: failed retrieving running-config data

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/ChangeLog.md

@@ -38,6 +38,8 @@ All notable changes to the project are documented in this file.
   exposing the set of PMD types currently supported.  Useful for SFP/SFP+
   diagnosis: an LR-only optic narrows the list to a single entry, confirming
   the transceiver without `ethtool -m`
+- New CLI command `show operational`, and XPath filtering for this and any of
+  the other datastores, using `[path /path/to/subtree]`
 
 ### Fixes
 

src/bin/copy.c

@@ -283,6 +283,7 @@ static void rmtmp(const char *path)
 static void sysrepo_print_error(sr_session_ctx_t *sess)
 {
 	const sr_error_info_t *erri = NULL;
+	const char *msg;
 	int err;
 
 	if (!sess)
@@ -292,7 +293,10 @@ static void sysrepo_print_error(sr_session_ctx_t *sess)
 	if (err || !erri || !erri->err_count)
 		return;
 
-	warnx("%s (%d)", erri->err->message, erri->err->err_code);
+	msg = erri->err->message;
+	if (!msg)
+		msg = sr_strerror(erri->err->err_code);
+	warnx("%s (%d)", msg, erri->err->err_code);
 }
 
 /* Connect to sysrepo and create NACM-aware session on running datastore */

src/bin/show/__init__.py

@@ -17,17 +17,18 @@ def get_json(xpath: str, datastore: str = "operational", quiet: bool = False) ->
             print("Invalid XPATH. It must be a valid string starting with '/'.")
         return {}
 
-    try:
-        result = subprocess.run(["copy", datastore, "-x", shlex.quote(xpath)],
-                                capture_output=True, text=True, check=True)
-        if not result.stdout.strip():
-            return {}
-        json_data = json.loads(result.stdout)
-        return json_data
-    except subprocess.CalledProcessError as e:
-        if not quiet:
-            print(f"Error running copy: {e}")
+    result = subprocess.run(["copy", datastore, "-x", shlex.quote(xpath)],
+                            capture_output=True, text=True)
+    if result.returncode != 0:
+        # copy already wrote a 'failed retrieving …' message (and a
+        # sysrepo error line) to stderr; relay it verbatim.
+        if not quiet and result.stderr:
+            print(result.stderr.rstrip())
         return {}
+    if not result.stdout.strip():
+        return {}
+    try:
+        return json.loads(result.stdout)
     except json.JSONDecodeError as e:
         if not quiet:
             print(f"Error parsing JSON output: {e}")

src/klish-plugin-infix/xml/infix.xml

@@ -737,15 +737,39 @@ echo "Public:  $pub"
   </COMMAND>
 
   <COMMAND name="factory-config" help="Show factory-config">
-    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy factory | jq -C . |pager</ACTION>
+    <SWITCH name="optional" min="0">
+      <COMMAND name="path" help="Filter by XPath, e.g. /ietf-interfaces:interfaces">
+        <PARAM name="xpath" ptype="/STRING" help="XPath into the datastore"/>
+      </COMMAND>
+    </SWITCH>
+    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy factory ${KLISH_PARAM_xpath:+-x $KLISH_PARAM_xpath} | jq -C . |pager</ACTION>
   </COMMAND>
 
   <COMMAND name="running-config" help="Show running-config">
-    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy running | jq -C . |pager</ACTION>
+    <SWITCH name="optional" min="0">
+      <COMMAND name="path" help="Filter by XPath, e.g. /ietf-interfaces:interfaces">
+        <PARAM name="xpath" ptype="/STRING" help="XPath into the datastore"/>
+      </COMMAND>
+    </SWITCH>
+    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy running ${KLISH_PARAM_xpath:+-x $KLISH_PARAM_xpath} | jq -C . |pager</ACTION>
   </COMMAND>
 
   <COMMAND name="startup-config" help="Show startup-config">
-    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy startup | jq -C . |pager</ACTION>
+    <SWITCH name="optional" min="0">
+      <COMMAND name="path" help="Filter by XPath, e.g. /ietf-interfaces:interfaces">
+        <PARAM name="xpath" ptype="/STRING" help="XPath into the datastore"/>
+      </COMMAND>
+    </SWITCH>
+    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy startup ${KLISH_PARAM_xpath:+-x $KLISH_PARAM_xpath} | jq -C . |pager</ACTION>
+  </COMMAND>
+
+  <COMMAND name="operational" help="Show operational data (running config + system state)">
+    <SWITCH name="optional" min="0">
+      <COMMAND name="path" help="Filter by XPath, e.g. /ietf-interfaces:interfaces">
+        <PARAM name="xpath" ptype="/STRING" help="XPath into the datastore"/>
+      </COMMAND>
+    </SWITCH>
+    <ACTION sym="script" in="tty" out="tty" interrupt="true">copy operational ${KLISH_PARAM_xpath:+-x $KLISH_PARAM_xpath} | jq -C . |pager</ACTION>
   </COMMAND>
 
   <COMMAND name="firewall" help="Show firewall status and configuration">