subquery and more detailed error message added

doc/api/magic-snippets.md

@@ -81,25 +81,36 @@ Arguments:
 `-A`/`--delete-force-all` Force delete a snippet and all dependent snippets.
 
 ```{code-cell} ipython3
-gentoo_snippet = %sqlcmd snippets gentoo
-print(gentoo_snippet)
+chinstrap_snippet = %sqlcmd snippets chinstrap
+print(chinstrap_snippet)
 ```
 
-This returns the stored snippet `gentoo`.
+This returns the stored snippet `chinstrap`.
+
+Calling `%sqlcmd snippets {snippet_name}` also works on a snippet that is dependent on others. To demonstrate it, let's create a snippet dependent on `chinstrap` snippet.
+
+```{code-cell} ipython3
+%%sql --save chinstrap_sub
+SELECT * FROM chinstrap where island == 'Dream'
+```
+
+```{code-cell} ipython3
+chinstrap_sub_snippet = %sqlcmd snippets chinstrap_sub
+print(chinstrap_sub_snippet)
+```
+
+This returns the stored snippet `chinstrap_sub`.
 
 ```{code-cell} ipython3
 %sqlcmd snippets -d gentoo
 ```
 
 This deletes the stored snippet `gentoo`.
 
-To demonstrate `force-delete` let's create a snippet dependent on `chinstrap` snippet.
+To demonstrate `force-delete` let's first confirm there is a snippet dependent on `chinstrap` snippet.
 
 ```{code-cell} ipython3
-:tags: [hide-output]
-
-%%sql --save chinstrap_sub
-SELECT * FROM chinstrap where island == 'Dream'
+%sqlcmd snippets
 ```
 
 Trying to delete the `chinstrap` snippet will display an error message:
@@ -110,7 +121,7 @@ Trying to delete the `chinstrap` snippet will display an error message:
 %sqlcmd snippets -d chinstrap
 ```
 
-If you still wish to delete this snippet, you can run the below command:
+If you still wish to delete this snippet, you should use `force-delete` by running the below command:
 
 ```{code-cell} ipython3
 %sqlcmd snippets -D chinstrap

src/sql/cmd/snippets.py

@@ -68,13 +68,24 @@ def snippets(others):
         if others[0] in all_snippets:
             return str(store[others[0]])
 
-        if len(all_snippets) < 3:
-            snippets_format = " and ".join(all_snippets)
+        base_err_msg = f"'{others[0]}' is not a snippet. "
+        if len(all_snippets) == 0:
+            err_msg = "%sThere is no available snippet."
+        elif len(all_snippets) < 3:
+            err_msg = (
+                "%sAvailable snippets are "
+                f"{' and '.join(all_snippets)}."
+            )
         else:
-            snippets_format = f"{', '.join(all_snippets[:-1])}, and {all_snippets[-1]}"
+            err_msg = (
+                "%sAvailable snippets are "
+                f"{', '.join(all_snippets[:-1])}, and "
+                f"{all_snippets[-1]}."
+            )
+        err_msg = err_msg % (base_err_msg)
+
         raise UsageError(
-            f"'{others[0]}' is not a snippet. "
-            f"Available snippets are {snippets_format}"
+            err_msg
         )
 
     args = parser.parse_args(others)

src/tests/test_magic_cmd.py

@@ -429,17 +429,22 @@ def test_snippet(ip_snippets):
             "%sqlcmd snippets invalid",
             (
                 "'invalid' is not a snippet. Available snippets are high_price, "
-                "high_price_a, and high_price_b"
+                "high_price_a, and high_price_b."
             ),
         ),
         (
             "%sqlcmd snippets -d high_price_b",
             "%sqlcmd snippets invalid",
             (
                 "'invalid' is not a snippet. Available snippets are high_price "
-                "and high_price_a"
+                "and high_price_a."
             ),
         ),
+        (
+            "%sqlcmd snippets -A high_price",
+            "%sqlcmd snippets invalid",
+            "'invalid' is not a snippet. There is no available snippet."
+        )
     ],
 )
 def test_invalid_snippet(ip_snippets, precmd, cmd, err_msg):