Implements FHIRPath string join (stu) (medplum#4683)

* Implements FHIRPath string join (stu) * Update packages/core/src/fhirpath/functions.ts Co-authored-by: Matt Long <[email protected]> --------- Co-authored-by: Matt Long <[email protected]>
sahinf · Jun 18, 2024 · b33716e · b33716e
1 parent c42ca52
commit b33716e
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diff --git a/packages/core/src/fhirpath/atoms.ts b/packages/core/src/fhirpath/atoms.ts
@@ -32,7 +32,7 @@ export class FhirPathAtom implements Atom {
  return this.child.eval(context, []);
  }
  } catch (error) {
- throw new Error(`FhirPathError on "${this.original}": ${error}`);
+ throw new Error(`FhirPathError on "${this.original}": ${error}`, { cause: error });
  }
  }
 

diff --git a/packages/core/src/fhirpath/functions.test.ts b/packages/core/src/fhirpath/functions.test.ts
@@ -571,6 +571,26 @@ describe('FHIRPath functions', () => {
  expect(functions.toChars(context, [toTypedValue('xyz')])).toEqual([TYPED_X, TYPED_Y, TYPED_Z]);
  });
 
+ // Additional string functions
+ // STU Note: the contents of this section are Standard for Trial Use (STU)
+
+ test('join', () => {
+ expect(functions.join(context, [toTypedValue('')])).toEqual([toTypedValue('')]);
+ expect(functions.join(context, [toTypedValue('a'), toTypedValue('b'), toTypedValue('c')])).toEqual([
+ toTypedValue('abc'),
+ ]);
+ expect(
+ functions.join(
+ context,
+ [toTypedValue('a'), toTypedValue('b'), toTypedValue('c')],
+ new LiteralAtom(toTypedValue(','))
+ )
+ ).toEqual([toTypedValue('a,b,c')]);
+ expect(() => functions.join(context, [toTypedValue('')], new LiteralAtom(toTypedValue(1)))).toThrow(
+ 'Separator must be a string'
+ );
+ });
+
  // 5.7. Math
 
  test('abs', () => {

diff --git a/packages/core/src/fhirpath/functions.ts b/packages/core/src/fhirpath/functions.ts
@@ -1327,6 +1327,41 @@ export const functions: Record<string, FhirPathFunction> = {
  return applyStringFunc((str) => (str ? str.split('') : undefined), context, input);
  },
 
+ /*
+ * Additional string functions
+ * See: https://build.fhir.org/ig/HL7/FHIRPath/#additional-string-functions
+ * STU Note: the contents of this section are Standard for Trial Use (STU)
+ */
+
+ encode: stub,
+ decode: stub,
+ escape: stub,
+ unescape: stub,
+ trim: stub,
+ split: stub,
+
+ /**
+ * The join function takes a collection of strings and joins them into a single string, optionally using the given separator.
+ *
+ * If the input is empty, the result is empty.
+ *
+ * If no separator is specified, the strings are directly concatenated.
+ *
+ * See: https://build.fhir.org/ig/HL7/FHIRPath/#joinseparator-string--string
+ *
+ * @param context - The evaluation context.
+ * @param input - The input collection.
+ * @param separatorAtom - Optional separator atom.
+ * @returns The joined string.
+ */
+ join: (context: AtomContext, input: TypedValue[], separatorAtom: Atom): TypedValue[] => {
+ const separator = separatorAtom?.eval(context, getRootInput(context))[0]?.value ?? '';
+ if (typeof separator !== 'string') {
+ throw new Error('Separator must be a string.');
+ }
+ return [{ type: PropertyType.string, value: input.map((i) => i.value?.toString() ?? '').join(separator) }];
+ },
+
  /*
  * 5.7. Math
  */