commit 1ba5e7e28248b0722bac048ccd2268e9579e78a2
parent d4b23c48b8eebc449295c93a9a146ac506b0831a
Author: Erik Loualiche <eloualic@umn.edu>
Date: Fri, 13 Mar 2026 20:01:46 -0500
feat: align markdown table columns in xlcat output
Pad cells so pipe characters align vertically. Affects data tables,
schema tables, and describe output. Column widths computed from headers
and all data rows including head+tail.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Diffstat:
4 files changed, 140 insertions(+), 119 deletions(-)
diff --git a/demo/xlcat.gif b/demo/xlcat.gif
Binary files differ.
diff --git a/demo/xlset.gif b/demo/xlset.gif
Binary files differ.
diff --git a/src/formatter.rs b/src/formatter.rs
@@ -1,5 +1,6 @@
use crate::metadata::{format_file_size, FileInfo, SheetInfo};
use polars::prelude::*;
+use std::fmt::Write as FmtWrite;
// ---------------------------------------------------------------------------
// Public API
@@ -35,15 +36,13 @@ pub fn format_schema(sheet: &SheetInfo, df: &DataFrame) -> String {
"## Sheet: {} ({} rows x {} cols)\n\n",
sheet.name, data_rows, cols
);
- out.push_str("| Column | Type |\n");
- out.push_str("|--------|------|\n");
-
- for col in df.get_columns() {
- let name = col.name();
- let dtype = format_dtype(col.dtype());
- out.push_str(&format!("| {name} | {dtype} |\n"));
- }
-
+ let headers = vec!["Column".to_string(), "Type".to_string()];
+ let rows: Vec<Vec<String>> = df
+ .get_columns()
+ .iter()
+ .map(|col| vec![col.name().to_string(), format_dtype(col.dtype()).to_string()])
+ .collect();
+ out.push_str(&render_table(&headers, &rows));
out
}
@@ -69,43 +68,17 @@ pub fn format_sheet_listing(
out
}
-/// Render the full DataFrame as a markdown table.
+/// Render the full DataFrame as a markdown table with aligned columns.
pub fn format_data_table(df: &DataFrame) -> String {
- let columns = df.get_columns();
- let n_rows = df.height();
-
- // Header row
- let mut out = String::new();
- out.push('|');
- for col in columns {
- out.push_str(&format!(" {} |", col.name()));
- }
- out.push('\n');
-
- // Separator
- out.push('|');
- for _ in columns {
- out.push_str("---|");
- }
- out.push('\n');
-
- // Data rows
- for row_idx in 0..n_rows {
- out.push('|');
- for col in columns {
- let cell = format_cell(col, row_idx);
- out.push_str(&format!(" {cell} |"));
- }
- out.push('\n');
- }
-
- out
+ let (headers, rows) = df_to_strings(df);
+ render_table(&headers, &rows)
}
-/// Render head / tail view of a DataFrame.
+/// Render head / tail view of a DataFrame with aligned columns.
///
/// If total rows <= head_n + tail_n, shows all rows.
/// Otherwise shows first head_n rows, an omission line, then last tail_n rows.
+/// Column widths are computed from both head and tail so pipes stay aligned.
pub fn format_head_tail(df: &DataFrame, head_n: usize, tail_n: usize) -> String {
let total = df.height();
if total <= head_n + tail_n {
@@ -116,14 +89,18 @@ pub fn format_head_tail(df: &DataFrame, head_n: usize, tail_n: usize) -> String
let tail_df = df.tail(Some(tail_n));
let omitted = total - head_n - tail_n;
- let mut out = format_data_table(&head_df);
- out.push_str(&format!("... ({omitted} rows omitted) ...\n"));
- // Append tail rows without repeating the header
- let tail_table = format_data_table(&tail_df);
- // Skip header line + separator line of the tail table
- let tail_body = skip_table_header(&tail_table);
- out.push_str(tail_body);
+ let (headers, head_rows) = df_to_strings(&head_df);
+ let (_, tail_rows) = df_to_strings(&tail_df);
+ // Compute widths from both head and tail rows
+ let mut all_rows = head_rows.clone();
+ all_rows.extend(tail_rows.clone());
+ let widths = compute_col_widths(&headers, &all_rows);
+
+ let mut out = render_table_header(&headers, &widths);
+ out.push_str(&render_table_rows(&head_rows, &widths));
+ out.push_str(&format!("... ({omitted} rows omitted) ...\n"));
+ out.push_str(&render_table_rows(&tail_rows, &widths));
out
}
@@ -160,31 +137,19 @@ pub fn format_describe(df: &DataFrame) -> String {
let columns = df.get_columns();
let stats = ["count", "null_count", "mean", "std", "min", "max", "median", "unique"];
- // Header row
- let mut out = String::from("| stat |");
- for col in columns {
- out.push_str(&format!(" {} |", col.name()));
- }
- out.push('\n');
-
- // Separator
- out.push_str("|------|");
- for _ in columns {
- out.push_str("---|");
- }
- out.push('\n');
+ let mut headers = vec!["stat".to_string()];
+ headers.extend(columns.iter().map(|c| c.name().to_string()));
- // Stat rows
- for stat in &stats {
- out.push_str(&format!("| {stat} |"));
- for col in columns {
- let val = compute_stat(col, stat);
- out.push_str(&format!(" {val} |"));
- }
- out.push('\n');
- }
+ let rows: Vec<Vec<String>> = stats
+ .iter()
+ .map(|stat| {
+ let mut row = vec![stat.to_string()];
+ row.extend(columns.iter().map(|col| compute_stat(col, stat)));
+ row
+ })
+ .collect();
- out
+ render_table(&headers, &rows)
}
fn compute_stat(col: &Column, stat: &str) -> String {
@@ -261,6 +226,71 @@ fn is_numeric(dtype: &DataType) -> bool {
// Private helpers
// ---------------------------------------------------------------------------
+/// Extract headers and row data as strings from a DataFrame.
+fn df_to_strings(df: &DataFrame) -> (Vec<String>, Vec<Vec<String>>) {
+ let columns = df.get_columns();
+ let headers: Vec<String> = columns.iter().map(|c| c.name().to_string()).collect();
+ let rows: Vec<Vec<String>> = (0..df.height())
+ .map(|i| columns.iter().map(|c| format_cell(c, i)).collect())
+ .collect();
+ (headers, rows)
+}
+
+/// Compute the display width for each column.
+fn compute_col_widths(headers: &[String], rows: &[Vec<String>]) -> Vec<usize> {
+ let mut widths: Vec<usize> = headers.iter().map(|h| h.len().max(3)).collect();
+ for row in rows {
+ for (i, cell) in row.iter().enumerate() {
+ if i < widths.len() {
+ widths[i] = widths[i].max(cell.len());
+ }
+ }
+ }
+ widths
+}
+
+/// Render a markdown table header + separator line.
+fn render_table_header(headers: &[String], widths: &[usize]) -> String {
+ let mut out = String::new();
+ out.push('|');
+ for (i, h) in headers.iter().enumerate() {
+ let _ = write!(out, " {:<w$} |", h, w = widths[i]);
+ }
+ out.push('\n');
+ out.push('|');
+ for w in widths {
+ out.push('-');
+ for _ in 0..*w {
+ out.push('-');
+ }
+ out.push_str("-|");
+ }
+ out.push('\n');
+ out
+}
+
+/// Render markdown table data rows (no header).
+fn render_table_rows(rows: &[Vec<String>], widths: &[usize]) -> String {
+ let mut out = String::new();
+ for row in rows {
+ out.push('|');
+ for (i, cell) in row.iter().enumerate() {
+ let w = if i < widths.len() { widths[i] } else { cell.len() };
+ let _ = write!(out, " {:<w$} |", cell, w = w);
+ }
+ out.push('\n');
+ }
+ out
+}
+
+/// Render a complete aligned markdown table.
+fn render_table(headers: &[String], rows: &[Vec<String>]) -> String {
+ let widths = compute_col_widths(headers, rows);
+ let mut out = render_table_header(headers, &widths);
+ out.push_str(&render_table_rows(rows, &widths));
+ out
+}
+
/// Format a single cell value for markdown display.
fn format_cell(col: &Column, idx: usize) -> String {
match col.get(idx) {
@@ -307,23 +337,6 @@ fn format_dtype(dtype: &DataType) -> &'static str {
}
}
-/// Skip the first two lines (header + separator) of a markdown table string.
-fn skip_table_header(table: &str) -> &str {
- let mut newlines = 0;
- let mut pos = 0;
- for (i, ch) in table.char_indices() {
- if ch == '\n' {
- newlines += 1;
- pos = i + 1;
- if newlines == 2 {
- return &table[pos..];
- }
- }
- }
- // Fewer than 2 newlines — return empty
- ""
-}
-
/// Manual CSV fallback if CsvWriter is unavailable.
fn csv_fallback(df: &DataFrame) -> String {
let columns = df.get_columns();
@@ -387,8 +400,15 @@ mod tests {
let s2 = Series::new("value".into(), &[100i64, 200]);
let df = DataFrame::new(vec![s1.into_column(), s2.into_column()]).unwrap();
let out = format_data_table(&df);
- assert!(out.contains("| name | value |"));
- assert!(out.contains("| Alice | 100 |"));
+ assert!(out.contains("| name | value |"));
+ assert!(out.contains("| Alice | 100 |"));
+ // Verify pipes are aligned: all lines have same length
+ let lines: Vec<&str> = out.trim().lines().collect();
+ assert!(lines.len() >= 3);
+ let expected_len = lines[0].len();
+ for line in &lines {
+ assert_eq!(line.len(), expected_len, "Misaligned: {line}");
+ }
}
#[test]
@@ -397,8 +417,8 @@ mod tests {
let df = DataFrame::new(vec![s.into_column()]).unwrap();
let out = format_head_tail(&df, 25, 25);
assert!(!out.contains("omitted"));
- assert!(out.contains("| 1 |"));
- assert!(out.contains("| 3 |"));
+ assert!(out.contains("| 1 "));
+ assert!(out.contains("| 3 "));
}
#[test]
@@ -409,10 +429,10 @@ mod tests {
let df = DataFrame::new(vec![s.into_column()]).unwrap();
let out = format_head_tail(&df, 25, 25);
assert!(out.contains("(10 rows omitted)"));
- assert!(out.contains("| 1 |"));
- assert!(out.contains("| 25 |"));
- assert!(out.contains("| 36 |"));
- assert!(out.contains("| 60 |"));
+ assert!(out.contains("| 1 "));
+ assert!(out.contains("| 25 "));
+ assert!(out.contains("| 36 "));
+ assert!(out.contains("| 60 "));
}
#[test]
@@ -427,8 +447,8 @@ mod tests {
let df = DataFrame::new(vec![s1.into_column(), s2.into_column()]).unwrap();
let out = format_schema(&sheet, &df);
assert!(out.contains("## Sheet: Revenue (10 rows x 2 cols)"));
- assert!(out.contains("| date |"));
- assert!(out.contains("| amount |"));
+ assert!(out.contains("| date"));
+ assert!(out.contains("| amount"));
assert!(out.contains("String"));
assert!(out.contains("Float"));
}
@@ -465,24 +485,25 @@ mod tests {
let df = DataFrame::new(vec![s_name.into_column(), s_val.into_column()]).unwrap();
let out = format_describe(&df);
// Header row contains stat and column names
- assert!(out.contains("| stat |"));
- assert!(out.contains("| name |"));
- assert!(out.contains("| value |"));
+ assert!(out.contains("| stat"));
+ assert!(out.contains("name"));
+ assert!(out.contains("value"));
// All stat rows are present
- assert!(out.contains("| count |"));
- assert!(out.contains("| null_count |"));
- assert!(out.contains("| mean |"));
- assert!(out.contains("| std |"));
- assert!(out.contains("| min |"));
- assert!(out.contains("| max |"));
- assert!(out.contains("| median |"));
- assert!(out.contains("| unique |"));
+ assert!(out.contains("| count"));
+ assert!(out.contains("| null_count"));
+ assert!(out.contains("| mean"));
+ assert!(out.contains("| std"));
+ assert!(out.contains("| min"));
+ assert!(out.contains("| max"));
+ assert!(out.contains("| median"));
+ assert!(out.contains("| unique"));
// Non-numeric column shows "-" for mean
- assert!(out.contains("| mean | - |"));
- // Numeric column has a numeric mean value (not "-")
- // count=3 for both
- assert!(out.contains("| count | 3 | 3 |"));
- // unique=3 for both
- assert!(out.contains("| unique | 3 | 3 |"));
+ assert!(out.contains("| -"));
+ // Verify alignment: all table lines should have same length
+ let table_lines: Vec<&str> = out.trim().lines().filter(|l| l.starts_with('|')).collect();
+ let expected_len = table_lines[0].len();
+ for line in &table_lines {
+ assert_eq!(line.len(), expected_len, "Misaligned: {line}");
+ }
}
}
diff --git a/tests/test_integration.rs b/tests/test_integration.rs
@@ -21,8 +21,8 @@ fn test_simple_file_default() {
.stdout(predicate::str::contains("# File:"))
.stdout(predicate::str::contains("# Sheets: 1"))
.stdout(predicate::str::contains("## Sheet: Data"))
- .stdout(predicate::str::contains("| name |"))
- .stdout(predicate::str::contains("| Alice |"));
+ .stdout(predicate::str::contains("| name"))
+ .stdout(predicate::str::contains("| Alice"));
}
#[test]
@@ -36,9 +36,9 @@ fn test_schema_mode() {
.arg(path.to_str().unwrap())
.assert()
.success()
- .stdout(predicate::str::contains("| Column | Type |"))
- .stdout(predicate::str::contains("| name |"))
- .stdout(predicate::str::contains("| Alice |").not());
+ .stdout(predicate::str::contains("| Column"))
+ .stdout(predicate::str::contains("| name"))
+ .stdout(predicate::str::contains("Alice").not());
}
#[test]
