fix(template): allow partially resolved vars in arithmetic expressions

core/src/template-string/template-string.ts

@@ -69,7 +69,16 @@ interface ConditionalTree {
 }
 
 function getValue(v: Primitive | undefined | ResolvedClause) {
-  return isPlainObject(v) ? (<ResolvedClause>v).resolved : v
+  return isPlainObject(v) ? (v as ResolvedClause).resolved : v
+}
+
+function isPartiallyResolved(v: Primitive | undefined | ResolvedClause): boolean {
+  if (!isPlainObject(v)) {
+    return false
+  }
+
+  const clause = v as ResolvedClause
+  return !!clause.partial
 }
 
 export class TemplateError extends GardenError {
@@ -823,10 +832,16 @@ function buildBinaryExpression(head: any, tail: any) {
     if (rightRes && rightRes._error) {
       return rightRes
     }
-
     const left = getValue(leftRes)
     const right = getValue(rightRes)
 
+    // if any operand is partially resolved, preserve the original expression
+    const leftResPartial = isPartiallyResolved(leftRes)
+    const rightResPartial = isPartiallyResolved(rightRes)
+    if (leftResPartial || rightResPartial) {
+      return `${left} ${operator} ${right}`
+    }
+
     // Disallow undefined values for comparisons
     if (left === undefined || right === undefined) {
       const message = [leftRes, rightRes]

core/test/unit/src/template-string.ts

@@ -406,6 +406,58 @@ describe("resolveTemplateString", () => {
     })
   })
 
+  context("partial resolution in binary operators", () => {
+    context("arithmetic operators", () => {
+      const arithmeticOperators = ["-", "*", "/", "%", ">", ">=", "<", "<="]
+      for (const operator of arithmeticOperators) {
+        describe(`with ${operator} operator`, () => {
+          it("a missing reference as the first clause returns the original template", () => {
+            const res = resolveTemplateString({
+              string: `$\{var.foo ${operator} 2}`,
+              context: new TestContext({ var: {} }),
+              contextOpts: { allowPartial: true },
+            })
+            expect(res).to.equal(`$\{var.foo ${operator} 2}`)
+          })
+
+          it("a missing reference as the second clause returns the original template", () => {
+            const res = resolveTemplateString({
+              string: `$\{2 ${operator} var.foo}`,
+              context: new TestContext({ var: {} }),
+              contextOpts: { allowPartial: true },
+            })
+            expect(res).to.equal(`$\{2 ${operator} var.foo}`)
+          })
+        })
+      }
+    })
+
+    context("overloaded operators", () => {
+      const overLoadedOperators = ["+"]
+      for (const operator of overLoadedOperators) {
+        describe(`with ${operator} operator`, () => {
+          it(`a missing reference as the first clause returns the original template`, () => {
+            const res = resolveTemplateString({
+              string: `$\{var.foo ${operator} '2'}`,
+              context: new TestContext({ var: {} }),
+              contextOpts: { allowPartial: true },
+            })
+            expect(res).to.equal(`$\{var.foo ${operator} '2'}`)
+          })
+
+          it("a missing reference as the second clause returns the original template", () => {
+            const res = resolveTemplateString({
+              string: `$\{2 ${operator} var.foo}`,
+              context: new TestContext({ var: {} }),
+              contextOpts: { allowPartial: true },
+            })
+            expect(res).to.equal(`$\{2 ${operator} var.foo}`)
+          })
+        })
+      }
+    })
+  })
+
   it("should handle a positive equality comparison between equal resolved values", () => {
     const res = resolveTemplateString({ string: "${a == b}", context: new TestContext({ a: "a", b: "a" }) })
     expect(res).to.equal(true)