I broke up with neovim....vim is my best friend now

dot_vim/plugged/vimtex/test/test-indentation/test_math_input.tex

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+\documentclass{article}
+\usepackage{mathtools}
+\usepackage{amsmath}
+\usepackage{amssymb}
+\begin{document}
+
+\[
+  1+1
+      \]
+
+\begin{align}
+    2+2 = 4\\[1ex]
+        3+3 = 6
+    \end{align}
+
+\begin{equation}
+   \left(
+     f(x) = 3
+  \right)
+  \left.
+      f(x) = 3
+\right.
+\end{equation}
+
+Test $[ ... )$ of unmatched brackets in
+inline math text.
+
+In R, there is the operator \verb|[<-|...
+that ...
+
+\begin{equation*} 
+  \left \{ 
+    \begin{aligned}
+      -\Delta \theta &= u \quad \text{in } \Omega, \\
+      \theta &=0 \quad \text{on } \Gamma.
+    \end{aligned}
+  \right.
+\end{equation*}
+
+\begin{equation} \label{eq:state2}
+  \left\{
+    \begin{aligned}
+      -\div [a_M(z)\nabla y + b(\nabla y)]  &= u \quad \text{in } \Omega, \\
+      y &=0 \quad \text{on } \Gamma.
+    \end{aligned}
+  \right.
+\end{equation}
+
+\begin{equation}
+    \left\{
+        \begin{aligned}
+            \min_{u,y} &J(u,y) \\
+            \text{s.t.} \quad
+            &
+                -\Delta y = u \text{in } \Omega\\
+                y = 0 \text{on } \partial\Omega.
+             \\
+            &\begin{aligned}[t]
+                -\Delta y &= u && \text{in } \Omega\\
+                y &= 0 && \text{on } \partial\Omega.
+            \end{aligned}
+        \end{aligned}
+    \right.
+  \end{equation}
+
+\end{document}