Fix latex manipulation case with multiple formulas inside a single '$$' block (#9971)

* Changed the latex manipulation to only fix
single formulas.

* added news file

* Fixed an issue with multiple latex formulas in the
same '$$' block.

* reverted changes on old tests

Author: David Kutugata

news/2 Fixes/9766.md

@@ -0,0 +1 @@
+Fixed an issue with multiple latex formulas in the same '$$' block.

src/datascience-ui/interactive-common/latexManipulation.ts

@@ -31,6 +31,7 @@ export function fixLatexEquations(input: string): string {
         // Pick the first that matches
         let match = dollars;
         let isBeginMatch = false;
+        const isDollarsMatch = dollars?.index === dollar?.index;
         if (!match || (dollar && dollar.index < match.index)) {
             match = dollar;
             endRegex = /\$/;
@@ -58,8 +59,20 @@ export function fixLatexEquations(input: string): string {
                     // Invalid, just return
                     return input;
                 }
+            } else if (isDollarsMatch) {
+                // Output till the next $$
+                const offset = match.index + 2 + start;
+                const endDollar = endRegex.exec(input.substr(offset));
+                if (endDollar) {
+                    const length = endDollar.index + 2 + offset;
+                    output.push(input.substr(start, length));
+                    start = start + length;
+                } else {
+                    // Invalid, just return
+                    return input;
+                }
             } else {
-                // Output till the next $ or $$
+                // Output till the next $
                 const offset = match.index + 1 + start;
                 const endDollar = endRegex.exec(input.substr(offset));
                 if (endDollar) {

src/test/datascience/latexManipulation.unit.test.ts

@@ -89,9 +89,9 @@ $$
 $$
 \\begin{equation*}
 \\mathbf{V}_1 \\times \\mathbf{V}_2 = \\begin{vmatrix}
-\\mathbf{i} & \\mathbf{j} & \\mathbf{k} \\
-\\frac{\partial X}{\\partial u} & \\frac{\\partial Y}{\\partial u} & 0 \\\\
-\\frac{\partial X}{\\partial v} & \\frac{\\partial Y}{\\partial v} & 0
+\\mathbf{i} & \\mathbf{j} & \\mathbf{k} \\\\
+\\frac{\\partial X}{\\partial u} & \\frac{\\partial Y}{\\partial u} & 0 \\\\
+\\frac{\\partial X}{\\partial v} & \\frac{\\partial Y}{\\partial v} & 0
 \\end{vmatrix}
 \\end{equation*}
 $$
@@ -116,6 +116,42 @@ $$
 This expression $\\sqrt{3x-1}+(1+x)^2$ is an example of a TeX inline equation in a [Markdown-formatted](https://daringfireball.net/projects/markdown/) sentence.
 `;
 
+    const markdown6 = `$$
+\\begin{aligned}
+\\frac{\\partial}{\\partial\\omega_j}C(\\omega) &= \\frac1m\\sum_{i=1}^m\\varphi_j\\left(x^i\\right)\\left(\\varphi^T\\left(x^i\\right)\\omega-t^i\\right)
+= 0
+\\end{aligned}
+$$
+$$
+\\begin{pmatrix}
+\\varphi_j\\left(x^1\\right) & \\dots & \\varphi_j\\left(x^m\\right)
+\\end{pmatrix}
+\\begin{pmatrix}
+\\varphi_1\\left(x^1\\right) & \\dots & \\varphi_n\\left(x^1\\right)\\\\
+\\vdots & \\ddots & \\vdots\\\\
+\\varphi_1\\left(x^m\\right) & \\dots & \\varphi_n\\left(x^m\\right)
+\\end{pmatrix}
+\\begin{pmatrix}
+\\omega_1\\\\
+\\vdots\\\\
+\\omega_n
+\\end{pmatrix}
+=
+\\begin{pmatrix}
+\\varphi_j\\left(x^1\\right) & \\dots & \\varphi_j\\left(x^m\\right)
+\\end{pmatrix}
+\\begin{pmatrix}
+t^1\\\\
+\\vdots\\\\
+t^m
+\\end{pmatrix}
+$$
+
+Assuming that $T = (t^1, t^2, ..., t^m)^T$，$X = \\left(\\varphi(x^1), \\varphi(x^2), ..., \\varphi(x^m)\\right)^T$, then
+$$
+X^TX\\omega = X^TT
+$$`;
+
     test("Latex - Equations don't have $$", () => {
         const result = fixLatexEquations(markdown1);
         expect(result).to.be.equal(output1, 'Result is incorrect');
@@ -153,4 +189,9 @@ This expression $\\sqrt{3x-1}+(1+x)^2$ is an example of a TeX inline equation in
         const result = fixLatexEquations(markdown5);
         expect(result).to.be.equal(output5, 'Result is incorrect');
     });
+
+    test('Latex - Multiple /begins inside $$', () => {
+        const result = fixLatexEquations(markdown6);
+        expect(result).to.be.equal(markdown6, 'Result should not have changed');
+    });
 });