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[markdown] Simplify deindentation logic for fenced code block lines #2187

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Merged
merged 6 commits into from
Sep 30, 2025
Merged

[markdown] Simplify deindentation logic for fenced code block lines #2187

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d38eeaa
[markdown] Simplify deindentation logic for fenced code blocks
parlough Sep 30, 2025
9431ab9
Move function and add doc comment
parlough Sep 30, 2025
7d6a534
Merge branch 'main' into markdown/fenced-code-block-indent-handling
parlough Sep 30, 2025
f535f55
Rename `indexAfterRemovedSpaces` to `leadingSpacesCount`
parlough Sep 30, 2025
22e4d08
Reformat after applying rename
parlough Sep 30, 2025
1afcdc0
Add a small comment to changelog
parlough Sep 30, 2025
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1 change: 1 addition & 0 deletions pkgs/markdown/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
(https://dart-lang.github.io/tools).
* Update `package:web` API references in the example.
* Fix performance and correctness of HTML comment parser.
* Optimize indentation processing of fenced code blocks.
* Require Dart `^3.4.0`.

## 7.3.0
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26 changes: 20 additions & 6 deletions pkgs/markdown/lib/src/block_syntaxes/fenced_code_block_syntax.dart
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Expand Up @@ -4,6 +4,7 @@

import '../ast.dart';
import '../block_parser.dart';
import '../charcode.dart' show $space;
import '../line.dart';
import '../patterns.dart';
import '../util.dart';
Expand Down Expand Up @@ -50,11 +51,6 @@ class FencedCodeBlockSyntax extends BlockSyntax {
return Element('pre', [code]);
}

String _removeIndentation(String content, int length) {
final text = content.replaceFirst(RegExp('^\\s{0,$length}'), '');
return content.substring(content.length - text.length);
}

@override
List<Line> parseChildLines(
BlockParser parser, [
Expand All @@ -76,7 +72,7 @@ class FencedCodeBlockSyntax extends BlockSyntax {
!closingFence.marker.startsWith(openingMarker) ||
closingFence.hasInfo) {
childLines.add(
Line(_removeIndentation(parser.current.content, indent)),
Line(_removeLeadingSpaces(parser.current.content, upTo: indent)),
);
parser.advance();
} else {
Expand All @@ -95,6 +91,24 @@ class FencedCodeBlockSyntax extends BlockSyntax {

return childLines;
}

/// Removes the leading spaces (` `) from [content] up the given [upTo] count.
static String _removeLeadingSpaces(String content, {required int upTo}) {
var leadingSpacesCount = 0;

// Find the index of the first non-space character
// or the first space after the maximum removed specified by 'upTo'.
while (leadingSpacesCount < upTo && leadingSpacesCount < content.length) {
// We can just check for space (` `) since fenced code blocks
// consider spaces before the opening code fence as the
// indentation that should be removed.
if (content.codeUnitAt(leadingSpacesCount) != $space) {
break;
}
leadingSpacesCount += 1;
}
return content.substring(leadingSpacesCount);
}
}

class _FenceMatch {
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