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fix(array): Keep single empty row in AMS environments (#2947)

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* fix(array): Keep single empty row in AMS environments

In particular prevents empty equation-numbered environment (e.g. `{align}`)
from crashing.

Fix #2944

* Add tests

Co-authored-by: ylemkimon <y@ylem.kim>
This commit is contained in:
Erik Demaine
2021-04-24 15:28:16 -04:00
committed by GitHub
parent bc718a0658
commit 24332e053c
2 changed files with 21 additions and 2 deletions
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11
src/environments/array.js
View File

@@ -70,6 +70,7 @@ function parseArray(
colSeparationType,
addEqnNum,
singleRow,
emptySingleRow,
maxNumCols,
leqno,
}: {|
@@ -80,6 +81,7 @@ function parseArray(
colSeparationType?: ColSeparationType,
addEqnNum?: boolean,
singleRow?: boolean,
emptySingleRow?: boolean,
maxNumCols?: number,
leqno?: boolean,
|},
@@ -153,10 +155,12 @@ function parseArray(
parser.consume();
} else if (next === "\\end") {
// Arrays terminate newlines with `\crcr` which consumes a `\cr` if
// the last line is empty.
// the last line is empty. However, AMS environments keep the
// empty row if it's the only one.
// NOTE: Currently, `cell` is the last item added into `row`.
if (row.length === 1 && cell.type === "styling" &&
cell.body[0].body.length === 0) {
cell.body[0].body.length === 0 &&
(body.length > 1 || !emptySingleRow)) {
body.pop();
}
if (hLinesBeforeRow.length < body.length + 1) {
@@ -630,6 +634,7 @@ const alignedHandler = function(context, args) {
cols,
addJot: true,
addEqnNum: context.envName === "align" || context.envName === "alignat",
emptySingleRow: true,
colSeparationType: separationType,
maxNumCols: context.envName === "split" ? 2 : undefined,
leqno: context.parser.settings.leqno,
@@ -977,6 +982,7 @@ defineEnvironment({
addJot: true,
colSeparationType: "gather",
addEqnNum: context.envName === "gather",
emptySingleRow: true,
leqno: context.parser.settings.leqno,
};
return parseArray(context.parser, res, "display");
@@ -1009,6 +1015,7 @@ defineEnvironment({
validateAmsEnvironmentContext(context);
const res = {
addEqnNum: context.envName === "equation",
emptySingleRow: true,
singleRow: true,
maxNumCols: 1,
leqno: context.parser.settings.leqno,

12
test/katex-spec.js
View File

@@ -2797,6 +2797,18 @@ describe("AMS environments", function() {
expect`\begin{CD}A @<a<< B @>>b> C @>>> D\\@. @| @AcAA @VVdV \\@. E @= F @>>> G\end{CD}`.toBuild(displayMode);
});
it("should build an empty environment", () => {
expect`\begin{gather}\end{gather}`.toBuild(displayMode);
expect`\begin{gather*}\end{gather*}`.toBuild(displayMode);
expect`\begin{align}\end{align}`.toBuild(displayMode);
expect`\begin{align*}\end{align*}`.toBuild(displayMode);
expect`\begin{alignat}{2}\end{alignat}`.toBuild(displayMode);
expect`\begin{alignat*}{2}\end{alignat*}`.toBuild(displayMode);
expect`\begin{equation}\end{equation}`.toBuild(displayMode);
expect`\begin{split}\end{split}`.toBuild(displayMode);
expect`\begin{CD}\end{CD}`.toBuild(displayMode);
});
it("{equation} should fail if argument contains two rows.", () => {
expect`\begin{equation}a=\cr b+c\end{equation}`.not.toParse(displayMode);
});