Allow smart merging via expansion (#8)

To allow merging arrays and objects via expansion, trailing commas after `s`
and `q` will be auto removed after the expansion if no value is passed for the
placeholder.

Example:

```bash
jf "[%(a)*s, %(b)*s]" b=2 b=1

jf "{%(a)**s, %(b)**s}" b=2 b=1
```

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "jf"
-version = "0.4.0"
+version = "0.4.1"
 edition = "2021"
 authors = ["Arijit Basu <hi@arijitbasu.in>"]
 description = 'A small utility to safely format and print JSON objects in the commandline'

README.md

@@ -74,7 +74,8 @@ And [VALUE]... [NAME=VALUE]... [NAME@FILE]... are the values for the placeholder
 - Pass values for named key value pairs using `NAME=KEY_N NAME=VALUE_N` syntax.
 - Use `NAME@FILE` syntax to read from file where FILE can be `-` for stdin.
 - Do not declare or pass positional placeholders or values after named ones.
-- Expandable positional placeholder should be the last placeholder in a template.
+- To allow merging arrays and objects via expansion, trailing comma after `s` and `q`
+  will be auto removed after the expansion if no value is passed for the placeholder.
 
 ### EXAMPLES
 

assets/jf.1

@@ -98,7 +98,8 @@ Use `NAME@FILE` syntax to read from file where FILE can be `-` for stdin.
 .IP \(bu 3
 Do not declare or pass positional placeholders or values after named ones.
 .IP \(bu 3
-Expandable positional placeholder should be the last placeholder in a template.
+To allow merging arrays and objects via expansion, trailing comma after `s` and `q`
+will be auto removed after the expansion if no value is passed for the placeholder.
 .SH EXAMPLES
 
 .IP \(bu 3

src/lib.rs

@@ -124,7 +124,7 @@ fn read_named_placeholder<C, S>(
     chars: &mut C,
     named_values: &HashMap<String, Vec<String>>,
     stdin: &mut S,
-) -> Result<(), Error>
+) -> Result<bool, Error>
 where
     C: Iterator<Item = (usize, char)>,
     S: Iterator<Item = (usize, io::Result<Vec<u8>>)>,
@@ -138,6 +138,7 @@ where
     let mut is_nullable = false;
     let mut expand_items = false;
     let mut expand_pairs = false;
+    let mut empty_expansion = false;
 
     loop {
         let Some((col, ch)) = chars.next() else {
@@ -232,11 +233,11 @@ where
                     .enumerate();
 
                 if expand_pairs {
-                    read_positional_pairs_placeholder(
+                    empty_expansion = !read_positional_pairs_placeholder(
                         val, ch, col, false, &mut args, stdin,
                     )?;
                 } else if expand_items {
-                    read_positional_items_placeholder(
+                    empty_expansion = !read_positional_items_placeholder(
                         val, ch, col, false, &mut args, stdin,
                     )?;
                 } else {
@@ -272,7 +273,7 @@ where
         }
     }
 
-    Ok(())
+    Ok(empty_expansion)
 }
 
 fn collect_named_values<'a, A, S>(
@@ -367,15 +368,15 @@ fn read_positional_items_placeholder<'a, A, S>(
     is_stdin: bool,
     args: &mut A,
     stdin: &mut S,
-) -> Result<(), Error>
+) -> Result<bool, Error>
 where
     A: Iterator<Item = (usize, Cow<'a, str>)>,
     S: Iterator<Item = (usize, io::Result<Vec<u8>>)>,
 {
-    let mut is_empty = true;
+    let mut was_expanded = false;
 
     while let Ok((_, arg)) = read(is_stdin, col, args, stdin) {
-        is_empty = false;
+        was_expanded = true;
         if ch == 'q' {
             val.push_str(&json::to_string(&arg)?);
         } else {
@@ -384,10 +385,10 @@ where
         val.push(',');
     }
 
-    if !is_empty {
+    if was_expanded {
         val.pop();
     }
-    Ok(())
+    Ok(was_expanded)
 }
 
 fn read_positional_pairs_placeholder<'a, A, S>(
@@ -397,15 +398,15 @@ fn read_positional_pairs_placeholder<'a, A, S>(
     is_stdin: bool,
     args: &mut A,
     stdin: &mut S,
-) -> Result<(), Error>
+) -> Result<bool, Error>
 where
     A: Iterator<Item = (usize, Cow<'a, str>)>,
     S: Iterator<Item = (usize, io::Result<Vec<u8>>)>,
 {
     let mut is_reading_key = true;
-    let mut is_empty = true;
+    let mut was_expanded = false;
     while let Ok((_, arg)) = read(is_stdin, col, args, stdin) {
-        is_empty = false;
+        was_expanded = true;
         let arg = if is_reading_key || ch == 'q' {
             json::to_string(&arg)?
         } else {
@@ -429,10 +430,10 @@ where
             .into());
     }
 
-    if !is_empty {
+    if was_expanded {
         val.pop();
     }
-    Ok(())
+    Ok(was_expanded)
 }
 
 pub fn format_partial<'a, C, A, S>(
@@ -452,6 +453,7 @@ where
     let mut expand_items = false;
     let mut expand_pairs = false;
     let mut is_stdin = false;
+    let mut empty_expansion = false;
 
     while let Some((col, ch)) = chars.next() {
         // Reading a named placeholder
@@ -473,7 +475,8 @@ where
                     is_reading_named_values = true;
                     collect_named_values(args, stdin, &mut named_values)?;
                 };
-                read_named_placeholder(&mut val, chars, &named_values, stdin)?;
+                empty_expansion =
+                    read_named_placeholder(&mut val, chars, &named_values, stdin)?;
                 last_char = None;
             }
             ('*', Some('%')) if !expand_items && !expand_pairs => {
@@ -489,6 +492,10 @@ where
                 is_stdin = true;
                 last_char = Some('%');
             }
+            (',', None) if empty_expansion => {
+                empty_expansion = false;
+                last_char = None;
+            }
             (ch, Some('%')) if ch == 's' || ch == 'q' => {
                 if is_reading_named_values {
                     return Err(
@@ -499,19 +506,20 @@ where
                 };
 
                 if expand_items {
-                    read_positional_items_placeholder(
+                    empty_expansion = !read_positional_items_placeholder(
                         &mut val, ch, col, is_stdin, args, stdin,
                     )?;
                     expand_items = false;
                 } else if expand_pairs {
-                    read_positional_pairs_placeholder(
+                    empty_expansion = !read_positional_pairs_placeholder(
                         &mut val, ch, col, is_stdin, args, stdin,
                     )?;
                     expand_pairs = false;
                 } else {
                     read_positional_placeholder(
                         &mut val, ch, col, is_stdin, args, stdin,
                     )?;
+                    empty_expansion = false;
                 }
                 is_stdin = false;
                 last_char = None;
@@ -532,6 +540,7 @@ where
                 expand_items = false;
                 expand_pairs = false;
                 is_stdin = false;
+                empty_expansion = false;
             }
         }
     }

src/tests.rs

@@ -94,6 +94,36 @@ fn test_format_expand_pairs_from_stdin() {
     );
 }
 
+#[test]
+fn test_format_merge_arrays() {
+    let args = ["[%(a)*s, %(b)*s]"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), "[]");
+
+    let args = ["[%(a)*s, %(b)*s]", "a=1", "a=2"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), "[1,2]");
+
+    let args = ["[%(a)*s, %(b)*s]", "b=1", "b=2"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), "[1,2]");
+
+    let args = ["[%(a)*s, %(b)*s]", "a=1", "b=2", "a=3", "b=4"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), "[1,3,2,4]");
+}
+
+#[test]
+fn test_format_merge_objs() {
+    let args = ["{%(a)*s, %(b)*s}"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), "{}");
+
+    let args = ["{%(a)**s, %(b)**s}", "a=1", "a=2"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), r#"{"1":2}"#);
+
+    let args = ["{%(a)**s, %(b)**s}", "b=1", "b=2"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), r#"{"1":2}"#);
+
+    let args = ["{%(a)**s, %(b)**s}", "a=1", "b=2", "a=3", "b=4"].map(Into::into);
+    assert_eq!(jf::format(args).unwrap(), r#"{"1":3,"2":4}"#);
+}
+
 #[test]
 fn test_format_named() {
     let args = [
@@ -646,14 +676,14 @@ fn test_usage_example() {
 #[test]
 fn test_print_version() {
     let arg = ["jf v%v"].map(Into::into);
-    assert_eq!(jf::format(arg).unwrap(), r#""jf v0.4.0""#);
+    assert_eq!(jf::format(arg).unwrap(), r#""jf v0.4.1""#);
 
     let args =
         ["{foo: %q, bar: %(bar)q, version: %v}", "foo", "bar=bar"].map(Into::into);
 
     assert_eq!(
         jf::format(args).unwrap(),
-        r#"{"foo":"foo","bar":"bar","version":"0.4.0"}"#
+        r#"{"foo":"foo","bar":"bar","version":"0.4.1"}"#
     );
 }
 

src/usage.txt

@@ -37,7 +37,8 @@ RULES
   * Pass values for named key value pairs using `NAME=KEY_N NAME=VALUE_N` syntax.
   * Use `NAME@FILE` syntax to read from file where FILE can be `-` for stdin.
   * Do not declare or pass positional placeholders or values after named ones.
-  * Expandable positional placeholder should be the last placeholder in a template.
+  * To allow merging arrays and objects via expansion, trailing comma after `s` and `q`
+    will be auto removed after the expansion if no value is passed for the placeholder.
 
 EXAMPLES