Merge pull request #1545 from jqnatividad/fmt-nofinalnewline-option

`fmt`:  add `--no-final-newline` option

src/cmd/fmt.rs

@@ -24,6 +24,7 @@ fmt options:
     --quote-never              Never put quotes around any value.
     --escape <arg>             The escape character to use. When not specified,
                                quotes are escaped by doubling them.
+    --no-final-newline         Do not write a newline at the end of the output.
 
 Common options:
     -h, --help             Display this message
@@ -41,16 +42,17 @@ use crate::{
 
 #[derive(Deserialize)]
 struct Args {
-    arg_input:          Option<String>,
-    flag_out_delimiter: Option<Delimiter>,
-    flag_crlf:          bool,
-    flag_ascii:         bool,
-    flag_output:        Option<String>,
-    flag_delimiter:     Option<Delimiter>,
-    flag_quote:         Delimiter,
-    flag_quote_always:  bool,
-    flag_quote_never:   bool,
-    flag_escape:        Option<Delimiter>,
+    arg_input:             Option<String>,
+    flag_out_delimiter:    Option<Delimiter>,
+    flag_crlf:             bool,
+    flag_ascii:            bool,
+    flag_output:           Option<String>,
+    flag_delimiter:        Option<Delimiter>,
+    flag_quote:            Delimiter,
+    flag_quote_always:     bool,
+    flag_quote_never:      bool,
+    flag_escape:           Option<Delimiter>,
+    flag_no_final_newline: bool,
 }
 
 pub fn run(argv: &[&str]) -> CliResult<()> {
@@ -81,10 +83,50 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
 
     let mut rdr = rconfig.reader()?;
     let mut wtr = wconfig.writer()?;
-    let mut r = csv::ByteRecord::new();
-    while rdr.read_byte_record(&mut r)? {
-        wtr.write_byte_record(&r)?;
+    let mut wsconfig = (wconfig).clone();
+
+    wsconfig.path = Some(
+        tempfile::NamedTempFile::new()?
+            .into_temp_path()
+            .to_path_buf(),
+    );
+
+    let mut temp_writer = wsconfig.writer()?;
+    let mut current_record = csv::ByteRecord::new();
+    let mut next_record = csv::ByteRecord::new();
+    let mut is_last_record;
+    let mut records_exist = rdr.read_byte_record(&mut current_record)?;
+    while records_exist {
+        is_last_record = !rdr.read_byte_record(&mut next_record)?;
+        if is_last_record {
+            // If it's the last record and the --no-final-newline flag is set,
+            // write the record to a temporary file, then read the file into a string.
+            // Remove the last character (the newline) from the string, then write the string to the
+            // output.
+            temp_writer.write_record(&current_record)?;
+            temp_writer.flush()?;
+            let mut temp_string = match std::fs::read_to_string(
+                wsconfig.path.as_ref().ok_or("Temp file path not found")?,
+            ) {
+                Ok(s) => s,
+                Err(e) => return fail_clierror!("Error reading from temp file: {}", e),
+            };
+            if args.flag_no_final_newline {
+                temp_string.pop();
+            }
+            match wtr.into_inner() {
+                Ok(mut writer) => writer.write_all(temp_string.as_bytes())?,
+                Err(e) => return fail_clierror!("Error writing to output: {}", e),
+            };
+            break;
+        }
+        wtr.write_record(&current_record)?;
+        wtr.write_record(&next_record)?;
+        records_exist = rdr.read_byte_record(&mut current_record)?;
     }
-    wtr.flush()?;
+
+    // we don't flush the writer explicitly
+    // because it will cause a borrow error
+    // let's just let it drop and flush itself implicitly
     Ok(())
 }

src/config.rs

@@ -71,7 +71,7 @@ impl<'de> Deserialize<'de> for Delimiter {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct Config {
     pub path:          Option<PathBuf>, // None implies <stdin>
     idx_path:          Option<PathBuf>,

tests/test_fmt.rs

@@ -61,6 +61,39 @@ mnopqr,stuvwx\r
     assert_eq!(got, expected.to_string());
 }
 
+#[test]
+fn fmt_nofinalnewline() {
+    let (wrk, mut cmd) = setup("fmt_nofinalnewline");
+    cmd.arg("--no-final-newline");
+
+    let got: String = wrk.stdout(&mut cmd);
+    let expected = r#"h1,h2
+abcdef,ghijkl
+mnopqr,stuvwx
+"ab""cd""ef","gh,ij,kl""#;
+    assert_eq!(got, expected.to_string());
+}
+
+#[test]
+fn fmt_output() {
+    let (wrk, mut cmd) = setup("fmt_output");
+
+    let output_file = wrk.path("output.csv").to_string_lossy().to_string();
+
+    cmd.args(["--output", &output_file]);
+
+    wrk.assert_success(&mut cmd);
+
+    let got = wrk.read_to_string(&output_file);
+
+    let expected = r#"h1,h2
+abcdef,ghijkl
+mnopqr,stuvwx
+"ab""cd""ef","gh,ij,kl"
+"#;
+    assert_eq!(got, expected);
+}
+
 #[test]
 fn fmt_quote_always() {
     let (wrk, mut cmd) = setup("fmt_quote_always");