perf(custom): evaluate command lazily (starship#2173)

whi-tw · Jan 20, 2021 · 8302a3c · 8302a3c
1 parent bb160d9
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diff --git a/docs/config/README.md b/docs/config/README.md
@@ -2559,18 +2559,18 @@ If you have an interesting example not covered there, feel free to share it ther
 ### Options
 
 | Option        | Default                       | Description                                                                                                                |
-| ------------- | ----------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
-| `command`     |                               | The command whose output should be printed. The command will be passed on stdin to the shell.                              |
-| `when`        |                               | A shell command used as a condition to show the module. The module will be shown if the command returns a `0` status code. |
-| `shell`       |                               | [See below](#custom-command-shell)                                                                                         |
-| `description` | `"<custom module>"`           | The description of the module that is shown when running `starship explain`.                                               |
-| `files`       | `[]`                          | The files that will be searched in the working directory for a match.                                                      |
-| `directories` | `[]`                          | The directories that will be searched in the working directory for a match.                                                |
-| `extensions`  | `[]`                          | The extensions that will be searched in the working directory for a match.                                                 |
-| `symbol`      | `""`                          | The symbol used before displaying the command output.                                                                      |
-| `style`       | `"bold green"`                | The style for the module.                                                                                                  |
-| `format`      | `"[$symbol$output]($style) "` | The format for the module.                                                                                                 |
-| `disabled`    | `false`                       | Disables this `custom` module.                                                                                             |
+| ------------- | ------------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
+| `command`     |                                 | The command whose output should be printed. The command will be passed on stdin to the shell.                              |
+| `when`        |                                 | A shell command used as a condition to show the module. The module will be shown if the command returns a `0` status code. |
+| `shell`       |                                 | [See below](#custom-command-shell)                                                                                         |
+| `description` | `"<custom module>"`             | The description of the module that is shown when running `starship explain`.                                               |
+| `files`       | `[]`                            | The files that will be searched in the working directory for a match.                                                      |
+| `directories` | `[]`                            | The directories that will be searched in the working directory for a match.                                                |
+| `extensions`  | `[]`                            | The extensions that will be searched in the working directory for a match.                                                 |
+| `symbol`      | `""`                            | The symbol used before displaying the command output.                                                                      |
+| `style`       | `"bold green"`                  | The style for the module.                                                                                                  |
+| `format`      | `"[$symbol($output )]($style)"` | The format for the module.                                                                                                 |
+| `disabled`    | `false`                         | Disables this `custom` module.                                                                                             |
 
 ### Variables
 

diff --git a/src/configs/custom.rs b/src/configs/custom.rs
@@ -29,7 +29,7 @@ pub struct CustomConfig<'a> {
 impl<'a> RootModuleConfig<'a> for CustomConfig<'a> {
     fn new() -> Self {
         CustomConfig {
-            format: "[$symbol$output]($style) ",
+            format: "[$symbol($output )]($style)",
             symbol: "",
             command: "",
             when: None,

diff --git a/src/modules/custom.rs b/src/modules/custom.rs
@@ -46,36 +46,38 @@ pub fn module<'a>(name: &str, context: &'a Context) -> Option<Module<'a>> {
 
     let mut module = Module::new(name, config.description, Some(toml_config));
 
-    let output = exec_command(config.command, &config.shell.0)?;
-
-    let trimmed = output.trim();
-    if !trimmed.is_empty() {
-        let parsed = StringFormatter::new(config.format).and_then(|formatter| {
-            formatter
-                .map_meta(|var, _| match var {
-                    "symbol" => Some(config.symbol),
-                    _ => None,
-                })
-                .map_style(|variable| match variable {
-                    "style" => Some(Ok(config.style)),
-                    _ => None,
-                })
-                .map(|variable| match variable {
-                    // This may result in multiple calls to `get_module_version` when a user have
-                    // multiple `$version` variables defined in `format`.
-                    "output" => Some(Ok(trimmed)),
-                    _ => None,
-                })
-                .parse(None)
-        });
-
-        match parsed {
-            Ok(segments) => module.set_segments(segments),
-            Err(error) => {
-                log::warn!("Error in module `custom.{}`:\n{}", name, error);
-            }
-        };
-    }
+    let parsed = StringFormatter::new(config.format).and_then(|formatter| {
+        formatter
+            .map_meta(|var, _| match var {
+                "symbol" => Some(config.symbol),
+                _ => None,
+            })
+            .map_style(|variable| match variable {
+                "style" => Some(Ok(config.style)),
+                _ => None,
+            })
+            .map(|variable| match variable {
+                "output" => {
+                    let output = exec_command(config.command, &config.shell.0)?;
+                    let trimmed = output.trim();
+
+                    if trimmed.is_empty() {
+                        None
+                    } else {
+                        Some(Ok(trimmed.to_string()))
+                    }
+                }
+                _ => None,
+            })
+            .parse(None)
+    });
+
+    match parsed {
+        Ok(segments) => module.set_segments(segments),
+        Err(error) => {
+            log::warn!("Error in module `custom.{}`:\n{}", name, error);
+        }
+    };
     let elapsed = start.elapsed();
     log::trace!("Took {:?} to compute custom module {:?}", elapsed, name);
     module.duration = elapsed;