fix: dedent indented code blocks before formatting

mdsf/src/lib.rs

@@ -100,9 +100,9 @@ pub fn format_file(
                 let is_go = language == "go" || language == "golang";
 
                 let (is_snippet, code_snippet, snippet_lines) = if is_go {
-                    parse_go_codeblock(&mut lines)
+                    parse_go_codeblock(&mut lines, &indentation)
                 } else {
-                    parse_generic_codeblock(&mut lines)
+                    parse_generic_codeblock(&mut lines, &indentation)
                 };
 
                 if is_snippet {

mdsf/src/parser/mod.rs

@@ -5,7 +5,10 @@ use regex::Regex;
 const GO_TEMPORARY_PACKAGE_NAME: &str = "package mdsfformattertemporarynamespace\n";
 
 #[inline]
-pub fn parse_generic_codeblock(lines: &mut Enumerate<Lines>) -> (bool, String, usize) {
+pub fn parse_generic_codeblock(
+    lines: &mut Enumerate<Lines>,
+    indentation: &str,
+) -> (bool, String, usize) {
     let mut code_snippet = String::new();
 
     let mut is_snippet = false;
@@ -20,7 +23,7 @@ pub fn parse_generic_codeblock(lines: &mut Enumerate<Lines>) -> (bool, String, u
             break;
         }
 
-        code_snippet.push_str(subline);
+        code_snippet.push_str(dedent_line(subline, indentation));
 
         code_snippet.push(crate::config::LF_NEWLINE_CHAR);
     }
@@ -29,8 +32,11 @@ pub fn parse_generic_codeblock(lines: &mut Enumerate<Lines>) -> (bool, String, u
 }
 
 #[inline]
-pub fn parse_go_codeblock(lines: &mut Enumerate<Lines>) -> (bool, String, usize) {
-    let (is_snippet, mut code_snippet, snippet_lines) = parse_generic_codeblock(lines);
+pub fn parse_go_codeblock(
+    lines: &mut Enumerate<Lines>,
+    indentation: &str,
+) -> (bool, String, usize) {
+    let (is_snippet, mut code_snippet, snippet_lines) = parse_generic_codeblock(lines, indentation);
 
     if is_snippet && !GO_PACKAGE_RE.is_match(&code_snippet) {
         code_snippet.insert_str(0, GO_TEMPORARY_PACKAGE_NAME);
@@ -52,19 +58,85 @@ pub fn remove_go_package(snippet: String) -> String {
     }
 }
 
+#[inline]
+fn dedent_line<'a>(line: &'a str, indentation: &str) -> &'a str {
+    if indentation.is_empty() {
+        line
+    } else {
+        line.strip_prefix(indentation)
+            .unwrap_or_else(|| line.trim_start())
+    }
+}
+
 #[inline]
 pub fn indent_codeblock(indentation: &str, snippet: String) -> String {
     if indentation.is_empty() {
         snippet
     } else {
         snippet
             .lines()
-            .map(|line| format!("{indentation}{line}"))
+            .map(|line| {
+                if line.is_empty() {
+                    line.to_owned()
+                } else {
+                    format!("{indentation}{line}")
+                }
+            })
             .collect::<Vec<_>>()
             .join(crate::config::Newline::Lf.as_str())
     }
 }
 
+#[cfg(test)]
+mod test_parse_generic_codeblock {
+    use crate::parser::parse_generic_codeblock;
+
+    #[test]
+    fn it_should_remove_the_codeblock_indentation() {
+        let input = "    a = 1\n\n    b = 2\n    ```";
+
+        let (is_snippet, snippet, snippet_lines) =
+            parse_generic_codeblock(&mut input.lines().enumerate(), "    ");
+
+        assert!(is_snippet);
+        assert_eq!("a = 1\n\nb = 2\n", snippet);
+        assert_eq!(4, snippet_lines);
+    }
+
+    #[test]
+    fn it_should_keep_lines_of_unindented_codeblocks() {
+        let input = "a = 1\n  b = 2\n```";
+
+        let (is_snippet, snippet, snippet_lines) =
+            parse_generic_codeblock(&mut input.lines().enumerate(), "");
+
+        assert!(is_snippet);
+        assert_eq!("a = 1\n  b = 2\n", snippet);
+        assert_eq!(3, snippet_lines);
+    }
+}
+
+#[cfg(test)]
+mod test_indent_codeblock {
+    use crate::parser::indent_codeblock;
+
+    #[test]
+    fn it_should_indent_every_line() {
+        assert_eq!(
+            "    a = 1\n    b = 2",
+            indent_codeblock("    ", "a = 1\nb = 2".to_owned())
+        );
+    }
+
+    #[test]
+    fn it_should_not_indent_empty_lines() {
+        assert_eq!(
+            "    a = 1\n\n    b = 2",
+            indent_codeblock("    ", "a = 1\n\nb = 2".to_owned())
+        );
+    }
+}
+
 #[cfg(test)]
 mod test_go_package_re {
     use crate::parser::GO_PACKAGE_RE;