fix(cli): idx config prints JSON only when JSON is asked for

Auto output stays plain text when piped, as in 0.3.2, so scripts that
read $(idx config path) or $(idx config get KEY) keep working; -o json,
IDX_OUTPUT=json, or general.output = "json" print JSON. The config
goldens return to their 0.3.2 content.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3syn2fN2LNo5pvTSqc6eh

crates/idx-cli/src/cli/config.rs

@@ -1,7 +1,7 @@
 use clap::{Args, Subcommand};
 
 use crate::config::{config_path, ensure_default_config, get_config_value, set_config_value};
-use crate::output::{OutputFormat, json};
+use crate::output::{OutputSetting, json};
 use idx_core::error::IdxError;
 
 #[derive(Debug, Args)]
@@ -23,10 +23,11 @@ pub enum ConfigSubcommand {
     Path,
 }
 
-pub fn handle(cmd: &ConfigCmd, format: &OutputFormat) -> Result<(), IdxError> {
+pub fn handle(cmd: &ConfigCmd, setting: OutputSetting) -> Result<(), IdxError> {
-    // Each result as plain text, or one JSON document with -o json.
+    // Plain text, as scripts read `$(idx config path)`, unless JSON is asked
+    // for (-o json, IDX_OUTPUT, or general.output); auto stays text when piped.
     let print = |text: String, document: serde_json::Value| {
-        if format.is_json() {
+        if matches!(setting, OutputSetting::Json | OutputSetting::Jsonl) {
             json::print_json(&document)
         } else {
             println!("{}", crate::output::text::terminal_safe(&text));

crates/idx-cli/src/config.rs

@@ -14,6 +14,8 @@ use idx_core::error::IdxError;
 pub struct IdxConfig {
     pub core: CoreConfig,
     pub output: OutputFormat,
+    /// The setting `output` came from, before auto was resolved.
+    pub output_setting: OutputSetting,
     pub no_color: bool,
 }
 
@@ -32,7 +34,7 @@ impl IdxConfig {
     pub fn load_with_cli(cli: &Cli) -> Result<Self, IdxError> {
         let mut core = CoreConfig::load()?;
         core.verbose = cli.verbose > 0;
-        let mut output = OutputSetting::Auto.resolve(stdout_is_terminal());
+        let mut setting = OutputSetting::Auto;
         let mut no_color = false;
 
         let path = config_path()?;
@@ -41,8 +43,8 @@ impl IdxConfig {
             let parsed: FileConfig =
                 toml::from_str(&raw).map_err(|e| IdxError::ConfigError(e.to_string()))?;
             if let Some(general) = parsed.general {
-                if let Some(setting) = general.output {
+                if let Some(file_setting) = general.output {
-                    output = setting.resolve(stdout_is_terminal());
+                    setting = file_setting;
                 }
                 if let Some(color) = general.color {
                     no_color = !color;
@@ -51,25 +53,25 @@ impl IdxConfig {
         }
 
         if let Ok(value) = std::env::var("IDX_OUTPUT") {
-            let setting = OutputSetting::parse(&value).ok_or_else(|| {
+            setting = OutputSetting::parse(&value).ok_or_else(|| {
                 IdxError::ConfigError(format!(
                     "invalid IDX_OUTPUT value: '{value}', expected 'auto', 'table', 'json', or 'jsonl'"
                 ))
             })?;
-            output = setting.resolve(stdout_is_terminal());
         }
         if let Ok(value) = std::env::var("IDX_NO_COLOR") {
             no_color = value == "1" || value.eq_ignore_ascii_case("true");
         }
 
-        if let Some(setting) = cli.output {
+        if let Some(cli_setting) = cli.output {
-            output = setting.resolve(stdout_is_terminal());
+            setting = cli_setting;
         }
         no_color = no_color || cli.no_color || !stdout_is_terminal();
 
         Ok(Self {
             core,
-            output,
+            output: setting.resolve(stdout_is_terminal()),
+            output_setting: setting,
             no_color,
         })
     }

crates/idx-cli/src/main.rs

@@ -62,7 +62,7 @@ fn run() -> Result<(), IdxError> {
             }
         }
         Commands::Config(cfg) => {
-            if let Err(err) = cli::config::handle(cfg, &config.output) {
+            if let Err(err) = cli::config::handle(cfg, config.output_setting) {
                 emit_error(&err, &config.output);
                 return Err(err);
             }

crates/idx-cli/tests/cli.rs

@@ -980,6 +980,43 @@ fn config_set_and_get_provider_round_trip() {
         .stdout(predicate::str::contains("msn"));
 }
 
+#[test]
+fn config_prints_json_only_when_json_is_asked_for() {
+    // Piped with auto output, scripts read plain text: `$(idx config path)`.
+    let root = test_env_dir("config-output-format");
+    bin_with_root(&root)
+        .args(["config", "set", "general.provider", "msn"])
+        .assert()
+        .success()
+        .stdout("ok\n");
+    bin_with_root(&root)
+        .args(["config", "get", "general.provider"])
+        .assert()
+        .success()
+        .stdout("msn\n");
+
+    let flag = run_success_json(bin_with_root(&root).args([
+        "-o",
+        "json",
+        "config",
+        "get",
+        "general.provider",
+    ]));
+    assert_eq!(
+        flag,
+        serde_json::json!({"key": "general.provider", "value": "msn"})
+    );
+    let env = run_success_json(
+        bin_with_root(&root)
+            .env("IDX_OUTPUT", "json")
+            .args(["config", "path"]),
+    );
+    assert!(
+        env["path"].as_str().unwrap().ends_with("config.toml"),
+        "{env}"
+    );
+}
+
 #[test]
 fn config_set_and_get_ownership_db_path_round_trip() {
     let root = test_env_dir("config-ownership-db-path");

crates/idx-cli/tests/golden/config-get.golden

@@ -1,4 +1,4 @@
 exit: 0
 --- stdout
-{"key":"general.provider","value":"msn"}
+msn
 --- stderr

crates/idx-cli/tests/golden/config-init.golden

@@ -1,4 +1,4 @@
 exit: 0
 --- stdout
-{"path":"<ROOT>/config/idx/config.toml"}
+<ROOT>/config/idx/config.toml
 --- stderr

crates/idx-cli/tests/golden/config-path.golden

@@ -1,4 +1,4 @@
 exit: 0
 --- stdout
-{"path":"<ROOT>/config/idx/config.toml"}
+<ROOT>/config/idx/config.toml
 --- stderr

crates/idx-cli/tests/golden/config-set-output-jsonl.golden

@@ -1,4 +1,4 @@
 exit: 0
 --- stdout
-{"key":"general.output","ok":true,"value":"jsonl"}
+ok
 --- stderr

crates/idx-cli/tests/golden/config-set.golden

@@ -1,4 +1,4 @@
 exit: 0
 --- stdout
-{"key":"general.provider","ok":true,"value":"yahoo"}
+ok
 --- stderr

web/src/content/docs/start/config.md

@@ -22,6 +22,10 @@ idx config get cache.quote_ttl
 idx config path
 ```
 
+`idx config` prints plain text, even when piped, so `$(idx config path)` works
+in scripts. Ask for JSON with `-o json`, `IDX_OUTPUT=json`, or
+`output = "json"`.
+
 ```toml
 [general]
 provider = "msn"           # msn | yahoo