From 78e558c4aa4baa958062cff08d64038195457529 Mon Sep 17 00:00:00 2001
From: Adria Navarro <adria@budibase.com>
Date: Thu, 27 Feb 2025 14:16:52 +0100
Subject: [PATCH] Handle conditional arguments

---
 .../common/CodeEditor/validator/hbs.ts        | 33 +++++++++-
 .../CodeEditor/validator/tests/hbs.spec.ts    | 64 +++++++++++++++++++
 2 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/packages/builder/src/components/common/CodeEditor/validator/hbs.ts b/packages/builder/src/components/common/CodeEditor/validator/hbs.ts
index b954bb1e8f..357cb04a86 100644
--- a/packages/builder/src/components/common/CodeEditor/validator/hbs.ts
+++ b/packages/builder/src/components/common/CodeEditor/validator/hbs.ts
@@ -94,7 +94,15 @@ export function validateHbsTemplate(
             providedParamsCount++
           }
 
-          if (providedParamsCount !== expectedArguments.length) {
+          const optionalArgMatcher = new RegExp(/^\[(.+)\]$/)
+          const optionalArgs = expectedArguments.filter(a =>
+            optionalArgMatcher.test(a)
+          )
+
+          if (
+            !optionalArgs.length &&
+            providedParamsCount !== expectedArguments.length
+          ) {
             diagnostics.push({
               from,
               to,
@@ -105,6 +113,29 @@ export function validateHbsTemplate(
                 ", "
               )}), but got ${providedParamsCount}.`,
             })
+          } else if (optionalArgs.length) {
+            const maxArgs = expectedArguments.length
+            const minArgs = maxArgs - optionalArgs.length
+            const parameters = expectedArguments
+              .map(a => {
+                const test = optionalArgMatcher.exec(a)
+                if (!test?.[1]) {
+                  return a
+                }
+                return `${test[1]} (optional)`
+              })
+              .join(", ")
+            if (
+              minArgs > providedParamsCount ||
+              maxArgs < providedParamsCount
+            ) {
+              diagnostics.push({
+                from,
+                to,
+                severity: "error",
+                message: `Helper "${helperName}" expects between ${minArgs} to ${expectedArguments.length} parameters (${parameters}), but got ${providedParamsCount}.`,
+              })
+            }
           }
         }
 
diff --git a/packages/builder/src/components/common/CodeEditor/validator/tests/hbs.spec.ts b/packages/builder/src/components/common/CodeEditor/validator/tests/hbs.spec.ts
index 9484c7a4a5..95ec2e540e 100644
--- a/packages/builder/src/components/common/CodeEditor/validator/tests/hbs.spec.ts
+++ b/packages/builder/src/components/common/CodeEditor/validator/tests/hbs.spec.ts
@@ -138,5 +138,69 @@ describe("hbs validator", () => {
         },
       ])
     })
+
+    describe("optional parameters", () => {
+      it("supports empty parameters", () => {
+        const validators: CodeValidator = {
+          helperFunction: {
+            arguments: ["a", "b", "[c]"],
+          },
+        }
+        const text = "{{ helperFunction 1 99 }}"
+
+        const result = validateHbsTemplate(text, validators)
+        expect(result).toHaveLength(0)
+      })
+
+      it("supports valid parameters", () => {
+        const validators: CodeValidator = {
+          helperFunction: {
+            arguments: ["a", "b", "[c]"],
+          },
+        }
+        const text = "{{ helperFunction 1 99 'a' }}"
+
+        const result = validateHbsTemplate(text, validators)
+        expect(result).toHaveLength(0)
+      })
+
+      it("returns a valid message on missing parameters", () => {
+        const validators: CodeValidator = {
+          helperFunction: {
+            arguments: ["a", "b", "[c]"],
+          },
+        }
+        const text = "{{ helperFunction 1 }}"
+
+        const result = validateHbsTemplate(text, validators)
+        expect(result).toEqual([
+          {
+            from: 0,
+            message: `Helper "helperFunction" expects between 2 to 3 parameters (a, b, c (optional)), but got 1.`,
+            severity: "error",
+            to: 22,
+          },
+        ])
+      })
+
+      it("returns a valid message on too many parameters", () => {
+        const validators: CodeValidator = {
+          helperFunction: {
+            arguments: ["a", "b", "[c]"],
+          },
+        }
+        const text = "{{ helperFunction 1 2 3 4 }}"
+
+        const result = validateHbsTemplate(text, validators)
+        expect(result).toEqual([
+          {
+            from: 0,
+            message: `Helper "helperFunction" expects between 2 to 3 parameters (a, b, c (optional)), but got 4.`,
+            severity: "error",
+            to: 28,
+          },
+        ])
+      })
+    })
   })
 })