JS: introduce truncate utility

Esben Sparre Andreasen · Esben Sparre Andreasen · commit 244d8d5778a7 · 2018-10-26T15:20:58.000+02:00
diff --git a/javascript/ql/src/semmle/javascript/Util.qll b/javascript/ql/src/semmle/javascript/Util.qll
@@ -23,4 +23,14 @@ string pluralize(string noun, int n) {
     result = noun
   else
     result = noun + "s"
-}
+}
+
+/**
+ * Gets `str` or a truncated version of `str` with `explanation` appended if its length exceeds `maxLength`.
+ *
+ * For example, the truncation of `"long_string"` for `maxLength = 5` and explanation `" ..."` is `"long_ ..."`.
+ */
+bindingset[str, maxLength, explanation]
+string truncate(string str, int maxLength, string explanation) {
+  if str.length() > maxLength then result = str.prefix(maxLength) + explanation else result = str
+}
diff --git a/javascript/ql/test/library-tests/Util/truncate.expected b/javascript/ql/test/library-tests/Util/truncate.expected
@@ -0,0 +1 @@
+| y |  | X | XX | XXy |
diff --git a/javascript/ql/test/library-tests/Util/truncate.ql b/javascript/ql/test/library-tests/Util/truncate.ql
@@ -0,0 +1,3 @@
+import semmle.javascript.Util
+
+select truncate("X", 0, "y"), truncate("", 2, "y"), truncate("X", 2, "y"), truncate("XX", 2, "y"), truncate("XXX", 2, "y")

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+import semmle.javascript.Util`
	`2`	`+`
	`3`	`+select truncate("X", 0, "y"), truncate("", 2, "y"), truncate("X", 2, "y"), truncate("XX", 2, "y"), truncate("XXX", 2, "y")`