Merge pull request #26 from corn-config/feat/multiline-string

feat: trim whitespace from multi-line strings

assets/inputs/string_multiline.corn

@@ -0,0 +1,6 @@
+{
+    foo = "
+    hello
+    world
+    "
+}

assets/outputs/json/string.json

@@ -1,6 +1,6 @@
 {
   "foo": "bar",
-  "bar": "\"\\\n\r\t",
+  "bar": "\"\\\n",
   "baz": "a",
   "qux": ""
 }

assets/outputs/json/string_multiline.json

@@ -0,0 +1,3 @@
+{
+  "foo": "hello\nworld\n"
+}

assets/outputs/toml/string.toml

@@ -1,7 +1,7 @@
 foo = "bar"
-bar = """
-\"\\
-\r\t"""
+bar = '''
+"\
+'''
 baz = "a"
 qux = ""
 

assets/outputs/toml/string_multiline.toml

@@ -0,0 +1,5 @@
+foo = """
+hello
+world
+"""
+

assets/outputs/yaml/string.yml

@@ -1,5 +1,6 @@
 foo: bar
-bar: "\"\\\n\r\t"
+bar: |
+  "\
 baz: a
 qux: ''
 

assets/outputs/yaml/string_multiline.yml

@@ -0,0 +1,4 @@
+foo: |
+  hello
+  world
+

libcorn/src/parser.rs

@@ -124,6 +124,12 @@ impl<'a> CornParser<'a> {
             };
         }
 
+        let full_string = if full_string.contains('\n') {
+            trim_multiline_string(&full_string)
+        } else {
+            full_string
+        };
+
         Ok(Cow::Owned(full_string))
     }
 
@@ -315,6 +321,40 @@ impl<'a> CornParser<'a> {
     }
 }
 
+/// Takes a multiline string and trims the maximum amount of
+/// whitespace at the start of each line
+/// while preserving formatting.
+///
+/// Based on code from `indoc` crate:
+/// <https://github.com/dtolnay/indoc/blob/60b5fa29ba4f98b479713621a1f4ec96155caaba/src/unindent.rs#L15-L51>
+
+fn trim_multiline_string(string: &str) -> String {
+    let ignore_first_line = string.starts_with('\n') || string.starts_with("\r\n");
+
+    let spaces = string
+        .lines()
+        .skip(1)
+        .map(|line| line.chars().take_while(char::is_ascii_whitespace).count())
+        .min()
+        .unwrap_or_default();
+
+    let mut result = String::with_capacity(string.len());
+    for (i, line) in string.lines().enumerate() {
+        if i > 1 || (i == 1 && !ignore_first_line) {
+            result.push('\n');
+        }
+        if i == 0 {
+            // Do not un-indent anything on same line as opening quote
+            result.push_str(line);
+        } else if line.len() > spaces {
+            // Whitespace-only lines may have fewer than the number of spaces
+            // being removed
+            result.push_str(&line[spaces..]);
+        }
+    }
+    result
+}
+
 /// Parses the input string into a `Config`
 /// containing the resolved inputs
 /// and a map of values representing the top-level object.

libcorn/src/wasm.rs

@@ -10,7 +10,6 @@ use wasm_bindgen_test::*;
 #[wasm_bindgen]
 pub fn parse(corn: &str) -> Result<JsValue, JsValue> {
     console_error_panic_hook::set_once();
-
     let res = crate::parse(corn);
 
     match res {