From f7a927348d2c8f69b38406db5535b2d74f90ed6a Mon Sep 17 00:00:00 2001
From: Duane Nykamp <nykamp@umn.edu>
Date: Sat, 28 Oct 2023 22:25:59 -0500
Subject: [PATCH] solveequations handles invalid equation (#53)

---
 .../src/components/SolveEquations.js          | 17 +++++++++-
 .../e2e/tagSpecific/solveequations.cy.js      | 32 +++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/packages/doenetml-worker/src/components/SolveEquations.js b/packages/doenetml-worker/src/components/SolveEquations.js
index 20055188c..de7e3c9dc 100644
--- a/packages/doenetml-worker/src/components/SolveEquations.js
+++ b/packages/doenetml-worker/src/components/SolveEquations.js
@@ -266,7 +266,22 @@ export default class SolveEquations extends InlineComponent {
                         ["-", expression.tree[2]],
                     ])
                     .subscripts_to_strings();
-                let f_base = formula.f();
+
+                let f_base;
+                try {
+                    f_base = formula.f();
+                } catch (e) {
+                    let message =
+                        "Cannot solve equation as could not evaluate equation: " +
+                        expression.toString();
+                    let warnings = [{ message, level: 1 }];
+
+                    return {
+                        setValue: { allSolutions: [] },
+                        sendWarnings: warnings,
+                    };
+                }
+
                 let f = (x) => f_base({ [varName]: x });
 
                 let f_symbolic = (x) =>
diff --git a/packages/test-cypress/cypress/e2e/tagSpecific/solveequations.cy.js b/packages/test-cypress/cypress/e2e/tagSpecific/solveequations.cy.js
index 2f00a2ebb..78bd0ae49 100644
--- a/packages/test-cypress/cypress/e2e/tagSpecific/solveequations.cy.js
+++ b/packages/test-cypress/cypress/e2e/tagSpecific/solveequations.cy.js
@@ -1026,4 +1026,36 @@ describe("SolveEquations Tag Tests", function () {
             );
         });
     });
+
+    it("handle bad equation", () => {
+        cy.window().then(async (win) => {
+            win.postMessage(
+                {
+                    doenetML: `
+  <solveEquations name="solve">x_(2t)=1</solveEquations>
+  <p>Number of solutions: <copy source="solve.numSolutions" assignNames="num" /></p>
+  `,
+                },
+                "*",
+            );
+        });
+
+        cy.get(cesc("#\\/num")).should("have.text", 0);
+
+        cy.window().then(async (win) => {
+            let errorWarnings = await win.returnErrorWarnings1();
+
+            expect(errorWarnings.errors.length).eq(0);
+            expect(errorWarnings.warnings.length).eq(1);
+
+            expect(errorWarnings.warnings[0].message).contain(
+                `Cannot solve equation`,
+            );
+            expect(errorWarnings.warnings[0].level).eq(1);
+            expect(errorWarnings.warnings[0].doenetMLrange.lineBegin).eq(2);
+            expect(errorWarnings.warnings[0].doenetMLrange.charBegin).eq(3);
+            expect(errorWarnings.warnings[0].doenetMLrange.lineEnd).eq(2);
+            expect(errorWarnings.warnings[0].doenetMLrange.charEnd).eq(56);
+        });
+    });
 });