feat: prevent incidental output breaking structured output

src/alr/alr-commands.adb

@@ -23,6 +23,7 @@ with Alire.Solutions;
 with Alire.Toolchains;
 with Alire.Utils.Did_You_Mean;
 with Alire.Utils.Tables;
+with Alire.Utils.User_Input;
 
 with Alr.Commands.Action;
 with Alr.Commands.Build;
@@ -185,7 +186,8 @@ package body Alr.Commands is
                      Long_Switch => "--format?",
                      Argument    => "FORMAT",
                      Help        =>
-                       "Use structured output for tables (JSON, TOML, YAML)");
+                       "Use structured output for tables (JSON, TOML, YAML)."
+                       & " Implies -n and -q.");
 
       Define_Switch (Config,
                      No_Color'Access,
@@ -515,24 +517,30 @@ package body Alr.Commands is
               Alire.Utils.Did_You_Mean.Upper_Case);
 
       begin
-         if Structured_Format.all /= "unset" then
-            Alire.Utils.Tables.Structured_Output := True;
-         else
+         --  Do nothing if there is no `--format` argument (or in the unlikely
+         --  event `--formatunset` is passed)
+         if Structured_Format.all = "unset" then
             return;
          end if;
 
-         if Format_Str /= "" and then not Is_Valid (Format_Str) then
-            Reportaise_Wrong_Arguments
-              ("Unknown argument in --format" & Structured_Format.all
-               & "." & Suggest (Format_Str));
-         end if;
+         --  Enable structured output
+         Alire.Utils.Tables.Structured_Output := True;
 
-         if Format_Str /= "" then
+         --  Set the output format, defaulting to JSON if unspecified.
+         if Format_Str = "" then
+            Alire.Utils.Tables.Structured_Output_Format := JSON;
+         elsif Is_Valid (Format_Str) then
             Alire.Utils.Tables.Structured_Output_Format
               := Alire.Utils.Tables.Formats'Value (Format_Str);
          else
-            Alire.Utils.Tables.Structured_Output_Format := JSON;
+            Reportaise_Wrong_Arguments
+              ("Unknown argument in --format" & Structured_Format.all
+               & "." & Suggest (Format_Str));
          end if;
+
+         --  Disable any additional messages/prompts which can render the
+         --  output unparsable
+         Alire.Utils.User_Input.Enable_Silent_Running;
       end Set_Structured_Output;
 
       use all type Alire.Platforms.Operating_Systems;

testsuite/tests/misc/structured-output-always-quiet/outdated_index/index/index.toml

@@ -0,0 +1 @@
+version = "1.1"

testsuite/tests/misc/structured-output-always-quiet/test.py

@@ -0,0 +1,33 @@
+"""Verify that structured output is not broken by extraneous output."""
+
+import json
+from drivers.alr import alr_settings_set, init_local_crate, run_alr
+from drivers.asserts import assert_substring, assert_eq, assert_not_substring
+
+
+# Load an an old (but compatible) index with the associated warning enabled.
+alr_settings_set("warning.old_index", "true")
+json_search = run_alr("--format=json", "search", "--list", quiet=False)
+plain_search = run_alr("search", "--list", quiet=False)
+
+# The warning should be included in the plain output, but not in the formatted
+# output, which should parse as valid JSON.
+assert_substring("is older than the newest supported by alr", plain_search.out)
+assert_not_substring("is older than the newest supported by alr", json_search.out)
+parsed_search = json.loads(json_search.out)
+assert_eq(["hello", "libhello"], [c["name"] for c in parsed_search])
+
+
+# Run `alr show` on a local crate with no toolchain configured and the toolchain
+# assistant enabled.
+init_local_crate(name="local_crate_name")
+alr_settings_set("toolchain.assistant", "true")
+p = run_alr("--format=json", "show", quiet=False)
+
+# The toolchain assistant should not output anything that breaks JSON parsing.
+assert_not_substring("toolchain", p.out)
+parsed_show = json.loads(p.out)
+assert_eq("local_crate_name", parsed_show["name"])
+
+
+print("SUCCESS")

testsuite/tests/misc/structured-output-always-quiet/test.yaml

@@ -0,0 +1,6 @@
+driver: python-script
+indexes:
+    outdated_index:
+        in_fixtures: false
+    basic_index:
+        in_fixtures: true