ls: Handle the use of QUOTING_STYLE variable

src/uu/ls/src/ls.rs

@@ -621,7 +621,52 @@ fn extract_hyperlink(options: &clap::ArgMatches) -> bool {
     }
 }
 
+/// Match the argument given to --quoting-style or the QUOTING_STYLE env variable.
+///
+/// # Arguments
+///
+/// * `style`: the actual argument string
+/// * `show_control` - A boolean value representing whether or not to show control characters.
+///
+/// # Returns
+///
+/// * An option with None if the style string is invalid, or a `QuotingStyle` wrapped in `Some`.
+fn match_quoting_style_name(style: &str, show_control: bool) -> Option<QuotingStyle> {
+    match style {
+        "literal" => Some(QuotingStyle::Literal { show_control }),
+        "shell" => Some(QuotingStyle::Shell {
+            escape: false,
+            always_quote: false,
+            show_control,
+        }),
+        "shell-always" => Some(QuotingStyle::Shell {
+            escape: false,
+            always_quote: true,
+            show_control,
+        }),
+        "shell-escape" => Some(QuotingStyle::Shell {
+            escape: true,
+            always_quote: false,
+            show_control,
+        }),
+        "shell-escape-always" => Some(QuotingStyle::Shell {
+            escape: true,
+            always_quote: true,
+            show_control,
+        }),
+        "c" => Some(QuotingStyle::C {
+            quotes: quoting_style::Quotes::Double,
+        }),
+        "escape" => Some(QuotingStyle::C {
+            quotes: quoting_style::Quotes::None,
+        }),
+        _ => None,
+    }
+}
+
 /// Extracts the quoting style to use based on the options provided.
+/// If no options are given, it looks if a default quoting style is provided
+/// through the QUOTING_STYLE environment variable.
 ///
 /// # Arguments
 ///
@@ -632,38 +677,12 @@ fn extract_hyperlink(options: &clap::ArgMatches) -> bool {
 ///
 /// A QuotingStyle variant representing the quoting style to use.
 fn extract_quoting_style(options: &clap::ArgMatches, show_control: bool) -> QuotingStyle {
-    let opt_quoting_style = options.get_one::<String>(options::QUOTING_STYLE).cloned();
+    let opt_quoting_style = options.get_one::<String>(options::QUOTING_STYLE);
 
     if let Some(style) = opt_quoting_style {
-        match style.as_str() {
+        match match_quoting_style_name(style, show_control) {
-            "literal" => QuotingStyle::Literal { show_control },
+            Some(qs) => qs,
-            "shell" => QuotingStyle::Shell {
+            None => unreachable!("Should have been caught by Clap"),
-                escape: false,
-                always_quote: false,
-                show_control,
-            },
-            "shell-always" => QuotingStyle::Shell {
-                escape: false,
-                always_quote: true,
-                show_control,
-            },
-            "shell-escape" => QuotingStyle::Shell {
-                escape: true,
-                always_quote: false,
-                show_control,
-            },
-            "shell-escape-always" => QuotingStyle::Shell {
-                escape: true,
-                always_quote: true,
-                show_control,
-            },
-            "c" => QuotingStyle::C {
-                quotes: quoting_style::Quotes::Double,
-            },
-            "escape" => QuotingStyle::C {
-                quotes: quoting_style::Quotes::None,
-            },
-            _ => unreachable!("Should have been caught by Clap"),
         }
     } else if options.get_flag(options::quoting::LITERAL) {
         QuotingStyle::Literal { show_control }
@@ -675,9 +694,24 @@ fn extract_quoting_style(options: &clap::ArgMatches, show_control: bool) -> Quot
         QuotingStyle::C {
             quotes: quoting_style::Quotes::Double,
         }
-    } else if options.get_flag(options::DIRED) || !std::io::stdout().is_terminal() {
+    } else if options.get_flag(options::DIRED) {
+        QuotingStyle::Literal { show_control }
+    } else {
+        // If set, the QUOTING_STYLE environment variable specifies a default style.
+        if let Ok(style) = std::env::var("QUOTING_STYLE") {
+            match match_quoting_style_name(style.as_str(), show_control) {
+                Some(qs) => return qs,
+                None => eprintln!(
+                    "{}: Ignoring invalid value of environment variable QUOTING_STYLE: '{}'",
+                    std::env::args().next().unwrap_or("ls".to_string()),
+                    style
+                ),
+            }
+        }
+
         // By default, `ls` uses Literal quoting when
         // writing to a non-terminal file descriptor
+        if !std::io::stdout().is_terminal() {
             QuotingStyle::Literal { show_control }
         } else {
             // TODO: use environment variable if available
@@ -687,6 +721,7 @@ fn extract_quoting_style(options: &clap::ArgMatches, show_control: bool) -> Quot
                 show_control,
             }
         }
+    }
 }
 
 /// Extracts the indicator style to use based on the options provided.