Parse DIF-esque CSV (fixes #3230 h/t @lowkeyfish)

CHANGELOG.md

@@ -7,6 +7,7 @@ changes may not be included if they are not expected to break existing code.
 * Sheet Visibility for ODS / FODS (h/t @edemaine)
 * HTML DOM ingress support formulae (`data-f`)
 * Proper handling of XLSX encoded entities (h/t @inreoh)
+* Proper handling of invalid DIF sheets that match heuristics (h/t @lowkeyfish)
 
 ## v0.20.3
 

bits/40_harb.js

@@ -1138,3 +1138,17 @@ function read_wb_ID(d, opts) {
 	}
 }
 
+function read_wb_TABL(d, opts) {
+	var o = opts || {}, OLD_WTF = !!o.WTF; o.WTF = true;
+	try {
+		var out = DIF.to_workbook(d, o);
+		if(!out || !out.Sheets) throw "DIF bad workbook";
+		var ws = out.Sheets[out.SheetNames[0]];
+		if(!ws || !ws["!ref"]) throw "DIF empty worksheet";
+		o.WTF = OLD_WTF;
+		return out;
+	} catch(e) {
+		o.WTF = OLD_WTF;
+		return PRN.to_workbook(d, opts);
+	}
+}

bits/87_read.js

@@ -99,7 +99,7 @@ function readSync(data/*:RawData*/, opts/*:?ParseOpts*/)/*:Workbook*/ {
 			if(n[1] === 0x49 && n[2] === 0x2a && n[3] === 0x00) throw new Error("TIFF Image File is not a spreadsheet");
 			if(n[1] === 0x44) return read_wb_ID(d, o);
 			break;
-		case 0x54: if(n[1] === 0x41 && n[2] === 0x42 && n[3] === 0x4C) return DIF.to_workbook(d, o); break;
+		case 0x54: if(n[1] === 0x41 && n[2] === 0x42 && n[3] === 0x4C) return read_wb_TABL(d, o); break;
 		case 0x50: return (n[1] === 0x4B && n[2] < 0x09 && n[3] < 0x09) ? read_zip(d, o) : read_prn(data, d, o, str);
 		case 0xEF: return n[3] === 0x3C ? parse_xlml(d, o) : read_prn(data, d, o, str);
 		case 0xFF: