FileAttachment.dsv (#1172)

* FileAttachment.dsv

* document FileAttachment.dsv

Author: mbostock

docs/lib/csv.md

@@ -1,6 +1,6 @@
 # Comma-separated values
 
-To load a [comma-separated values](https://en.wikipedia.org/wiki/Comma-separated_values) (CSV) file, use [`FileAttachment`](../javascript/files). The `file.csv` and `file.tsv` methods are implemented using [D3](https://d3js.org/d3-dsv) and are based on [RFC 4180](https://datatracker.ietf.org/doc/html/rfc4180).
+To load a [comma-separated values](https://en.wikipedia.org/wiki/Comma-separated_values) (CSV) file, use [`FileAttachment`](../javascript/files)`.csv`. The `csv`, `tsv`, and `dsv` method implementations are based on [RFC 4180](https://datatracker.ietf.org/doc/html/rfc4180).
 
 ```js echo
 const gistemp = FileAttachment("gistemp.csv").csv({typed: true});
@@ -18,7 +18,7 @@ The column names are listed in the `columns` property:
 gistemp.columns
 ```
 
-You can also load a tab-separated values (TSV) file using [`FileAttachment`](../javascript/files):
+You can also load a tab-separated values (TSV) file using `FileAttachment.tsv`:
 
 ```js echo
 const capitals = FileAttachment("us-state-capitals.tsv").tsv({typed: true});
@@ -28,6 +28,12 @@ const capitals = FileAttachment("us-state-capitals.tsv").tsv({typed: true});
 Inputs.table(capitals)
 ```
 
+For a different delimiter, use `FileAttachment.dsv`. <a href="https://github.com/observablehq/framework/pull/1172" class="observablehq-version-badge" data-version="prerelease" title="Added in #1172"></a> For example, for semicolon separated values:
+
+```js run=false
+const capitals = FileAttachment("us-state-capitals.csv").dsv({delimiter: ";", typed: true});
+```
+
 ## Type coercion
 
 A common pitfall with CSV is that it is untyped: numbers, dates, booleans, and every other possible value are represented as text and there is no universal way to automatically determine the correct type.

src/client/stdlib/fileAttachment.js

@@ -21,12 +21,6 @@ async function remote_fetch(file) {
   return response;
 }
 
-async function dsv(file, delimiter, {array = false, typed = false} = {}) {
-  const [text, d3] = await Promise.all([file.text(), import("npm:d3-dsv")]);
-  const parse = delimiter === "\t" ? (array ? d3.tsvParseRows : d3.tsvParse) : array ? d3.csvParseRows : d3.csvParse;
-  return parse(text, typed && d3.autoType);
-}
-
 export class AbstractFile {
   constructor(name, mimeType = "application/octet-stream", lastModified) {
     Object.defineProperty(this, "name", {value: `${name}`, enumerable: true});
@@ -50,11 +44,17 @@ export class AbstractFile {
   async stream() {
     return (await remote_fetch(this)).body;
   }
+  async dsv({delimiter = ",", array = false, typed = false} = {}) {
+    const [text, d3] = await Promise.all([this.text(), import("npm:d3-dsv")]);
+    const format = d3.dsvFormat(delimiter);
+    const parse = array ? format.parseRows : format.parse;
+    return parse(text, typed && d3.autoType);
+  }
   async csv(options) {
-    return dsv(this, ",", options);
+    return this.dsv({...options, delimiter: ","});
   }
   async tsv(options) {
-    return dsv(this, "\t", options);
+    return this.dsv({...options, delimiter: "\t"});
   }
   async image(props) {
     const url = await this.url();