From e2a3dc17172ca15ec6876767183c3c8b5ca60c24 Mon Sep 17 00:00:00 2001
From: Oleg Baskakov <baskakov@google.com>
Date: Wed, 20 Mar 2024 23:12:00 -0700
Subject: [PATCH] Add strikethrough markdown support

Since it's inlined, the extension is added directly to the core module.
---
 gradle/libs.versions.toml                     |  1 +
 markdown/README.md                            |  2 +-
 markdown/core/build.gradle.kts                |  1 +
 .../markdown/processing/MarkdownProcessor.kt  |  2 +
 .../DefaultInlineMarkdownRenderer.kt          | 14 +++++
 .../markdown/rendering/MarkdownStyling.kt     |  1 +
 ...rkdownProcessorDocumentParsingExtraTest.kt | 52 +++++++++++++++++++
 .../markdown/styling/MarkdownIntUiStyling.kt  |  4 ++
 settings.gradle.kts                           |  2 +
 9 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 56b05fe54..1742767c2 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -16,6 +16,7 @@ poko = "0.13.1"
 
 [libraries]
 commonmark-core = { module = "org.commonmark:commonmark", version.ref = "commonmark" }
+commonmark-extGfmStrikethrough = { module = "org.commonmark:commonmark-ext-gfm-strikethrough", version.ref = "commonmark" }
 
 filePicker = { module = "com.darkrockstudios:mpfilepicker", version = "3.1.0" }
 
diff --git a/markdown/README.md b/markdown/README.md
index 6879c093d..d6caa3536 100644
--- a/markdown/README.md
+++ b/markdown/README.md
@@ -11,13 +11,13 @@ Currently supports the [CommonMark 0.31.2](https://spec.commonmark.org/0.31.2/)
 Additional supported Markdown, via extensions:
 
 * Alerts ([GitHub Flavored Markdown][alerts-specs]) — see [`extension-gfm-alerts`](extension/gfm-alerts)
+* Strikethrough(builtin) ([GitHub Flavored Markdown](https://github.github.com/gfm/#strikethrough-extension-))
 
 [alerts-specs]: https://github.com/orgs/community/discussions/16925
 
 On the roadmap, but not currently supported — in no particular order:
 
 * Tables ([GitHub Flavored Markdown](https://github.github.com/gfm/#tables-extension-))
-* Strikethrough ([GitHub Flavored Markdown](https://github.github.com/gfm/#strikethrough-extension-))
 * Image loading (via [Coil 3](https://coil-kt.github.io/coil/upgrading_to_coil3/))
 * Auto-linking ([GitHub Flavored Markdown](https://github.github.com/gfm/#autolinks-extension-))
 * Task list items ([GitHub Flavored Markdown](https://github.github.com/gfm/#task-list-items-extension-))
diff --git a/markdown/core/build.gradle.kts b/markdown/core/build.gradle.kts
index d784f1314..469f1a419 100644
--- a/markdown/core/build.gradle.kts
+++ b/markdown/core/build.gradle.kts
@@ -8,6 +8,7 @@ plugins {
 dependencies {
     api(projects.ui)
     api(libs.commonmark.core)
+    api(libs.commonmark.extGfmStrikethrough)
 
     testImplementation(compose.desktop.uiTestJUnit4)
     testImplementation(projects.ui)
diff --git a/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/processing/MarkdownProcessor.kt b/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/processing/MarkdownProcessor.kt
index 626920173..95bc7cb08 100644
--- a/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/processing/MarkdownProcessor.kt
+++ b/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/processing/MarkdownProcessor.kt
@@ -1,5 +1,7 @@
 package org.jetbrains.jewel.markdown.processing
 
+import org.commonmark.ext.gfm.strikethrough.Strikethrough
+import org.commonmark.ext.gfm.strikethrough.StrikethroughExtension
 import org.commonmark.node.Block
 import org.commonmark.node.BlockQuote
 import org.commonmark.node.BulletList
diff --git a/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/DefaultInlineMarkdownRenderer.kt b/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/DefaultInlineMarkdownRenderer.kt
index 94b11a1d6..ef2e63dca 100644
--- a/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/DefaultInlineMarkdownRenderer.kt
+++ b/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/DefaultInlineMarkdownRenderer.kt
@@ -7,6 +7,8 @@ import androidx.compose.ui.text.ExperimentalTextApi
 import androidx.compose.ui.text.SpanStyle
 import androidx.compose.ui.text.UrlAnnotation
 import androidx.compose.ui.text.buildAnnotatedString
+import org.commonmark.ext.gfm.strikethrough.Strikethrough
+import org.commonmark.ext.gfm.strikethrough.StrikethroughExtension
 import org.commonmark.renderer.text.TextContentRenderer
 import org.jetbrains.jewel.foundation.ExperimentalJewelApi
 import org.jetbrains.jewel.markdown.InlineMarkdown
@@ -17,8 +19,16 @@ public open class DefaultInlineMarkdownRenderer(rendererExtensions: List<Markdow
 
     public constructor(vararg extensions: MarkdownProcessorExtension) : this(extensions.toList())
 
+    private val strikethroughExtension = StrikethroughExtension.create()
+
+    private val commonMarkParser =
+        Parser.builder()
+            .extensions(listOf(strikethroughExtension))
+            .extensions(rendererExtensions.map { it.parserExtension }).build()
+
     private val plainTextRenderer =
         TextContentRenderer.builder()
+            .extensions(listOf(strikethroughExtension))
             .extensions(rendererExtensions.map { it.textRendererExtension })
             .build()
 
@@ -44,6 +54,10 @@ public open class DefaultInlineMarkdownRenderer(rendererExtensions: List<Markdow
                     withStyles(styling.emphasis, child) { appendInlineMarkdownFrom(it.children, styling) }
                 }
 
+                is Strikethrough -> {
+                    withStyles(styling.strikethrough, child) { appendInlineMarkdownFrom(it, styling) }
+                }
+
                 is InlineMarkdown.StrongEmphasis -> {
                     withStyles(styling.strongEmphasis, child) { appendInlineMarkdownFrom(it.children, styling) }
                 }
diff --git a/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/MarkdownStyling.kt b/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/MarkdownStyling.kt
index 28b23d79d..6a5bf4cb5 100644
--- a/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/MarkdownStyling.kt
+++ b/markdown/core/src/main/kotlin/org/jetbrains/jewel/markdown/rendering/MarkdownStyling.kt
@@ -292,6 +292,7 @@ public class InlinesStyling(
     public val link: SpanStyle,
     public val emphasis: SpanStyle,
     public val strongEmphasis: SpanStyle,
+    public val strikethrough: SpanStyle,
     public val inlineHtml: SpanStyle,
     public val renderInlineHtml: Boolean,
 ) {
diff --git a/markdown/core/src/test/kotlin/org/jetbrains/jewel/markdown/MarkdownProcessorDocumentParsingExtraTest.kt b/markdown/core/src/test/kotlin/org/jetbrains/jewel/markdown/MarkdownProcessorDocumentParsingExtraTest.kt
index 15bf4c97e..e0dc88c97 100644
--- a/markdown/core/src/test/kotlin/org/jetbrains/jewel/markdown/MarkdownProcessorDocumentParsingExtraTest.kt
+++ b/markdown/core/src/test/kotlin/org/jetbrains/jewel/markdown/MarkdownProcessorDocumentParsingExtraTest.kt
@@ -72,4 +72,56 @@ class MarkdownProcessorDocumentParsingExtraTest {
          */
         parsed.assertEquals(paragraph("*_*foo *bar* a*_*"))
     }
+
+    @Test
+    fun `should parse gfm spec example 491 correctly (Strikethrough)`() {
+        val parsed = processor.processMarkdownDocument("~~Hi~~ Hello, ~~there~~ world!")
+
+        /*
+         * Expected HTML:
+         * <p><del>Hi</del> Hello, <del>there</del> world!</p>
+         */
+        parsed.assertEquals(paragraph("~~Hi~~ Hello, ~~there~~ world\\!"))
+    }
+
+    @org.junit.Ignore("Strikethrough is any text wrapped in a pair of one tildes, but our implementation assumes two")
+    @Test
+    fun `should parse gfm spec example 491b correctly (Strikethrough)`() {
+        val parsed = processor.processMarkdownDocument("~there~ world!")
+
+        parsed.assertEquals(paragraph("~there~ world\\!"))
+    }
+
+    /** As with regular emphasis delimiters, a new paragraph will cause strikethrough parsing to cease */
+    @Test
+    fun `should parse gfm spec example 492 correctly (Strikethrough)`() {
+        val parsed = processor.processMarkdownDocument(
+            """
+            |This ~~has a
+            |
+            |new paragraph~~.
+            """.trimMargin(),
+        )
+
+        /*
+         * Expected HTML:
+         * <p>This ~~has a</p>
+         * <p>new paragraph~~.</p>
+         */
+        parsed.assertEquals(
+            paragraph("This \\~\\~has a"),
+            paragraph("new paragraph\\~\\~."),
+        )
+    }
+
+    @Test
+    fun `should parse gfm spec example 493 correctly (Strikethrough)`() {
+        val parsed = processor.processMarkdownDocument("This will ~~~not~~~ strike.")
+
+        /*
+         * Expected HTML:
+         * <p>This will ~~~not~~~ strike.</p>
+         */
+        parsed.assertEquals(paragraph("This will \\~\\~\\~not\\~\\~\\~ strike."))
+    }
 }
diff --git a/markdown/int-ui-standalone-styling/src/main/kotlin/org/jetbrains/jewel/intui/markdown/styling/MarkdownIntUiStyling.kt b/markdown/int-ui-standalone-styling/src/main/kotlin/org/jetbrains/jewel/intui/markdown/styling/MarkdownIntUiStyling.kt
index 1988411dc..d5f136561 100644
--- a/markdown/int-ui-standalone-styling/src/main/kotlin/org/jetbrains/jewel/intui/markdown/styling/MarkdownIntUiStyling.kt
+++ b/markdown/int-ui-standalone-styling/src/main/kotlin/org/jetbrains/jewel/intui/markdown/styling/MarkdownIntUiStyling.kt
@@ -587,6 +587,7 @@ public fun InlinesStyling.Companion.light(
         textStyle.copy(color = Color(0xFF0969DA), textDecoration = TextDecoration.Underline).toSpanStyle(),
     emphasis: SpanStyle = textStyle.copy(fontStyle = FontStyle.Italic).toSpanStyle(),
     strongEmphasis: SpanStyle = textStyle.copy(fontWeight = FontWeight.Bold).toSpanStyle(),
+    strikethrough: SpanStyle = textStyle.copy(textDecoration = TextDecoration.LineThrough).toSpanStyle().copy(),
     inlineHtml: SpanStyle = textStyle.toSpanStyle(),
     renderInlineHtml: Boolean = false,
 ): InlinesStyling =
@@ -596,6 +597,7 @@ public fun InlinesStyling.Companion.light(
         link,
         emphasis,
         strongEmphasis,
+        strikethrough,
         inlineHtml,
         renderInlineHtml,
     )
@@ -616,6 +618,7 @@ public fun InlinesStyling.Companion.dark(
             .toSpanStyle(),
     emphasis: SpanStyle = textStyle.copy(fontStyle = FontStyle.Italic).toSpanStyle(),
     strongEmphasis: SpanStyle = textStyle.copy(fontWeight = FontWeight.Bold).toSpanStyle(),
+    strikethrough: SpanStyle = textStyle.copy(textDecoration = TextDecoration.LineThrough).toSpanStyle().copy(),
     inlineHtml: SpanStyle = textStyle.toSpanStyle(),
     renderInlineHtml: Boolean = false,
 ): InlinesStyling =
@@ -625,6 +628,7 @@ public fun InlinesStyling.Companion.dark(
         link,
         emphasis,
         strongEmphasis,
+        strikethrough,
         inlineHtml,
         renderInlineHtml,
     )
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 7d7e33b08..9bc4f928d 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -51,3 +51,5 @@ gradleEnterprise {
         termsOfServiceAgree = "yes"
     }
 }
+include("markdown:commonmark-extensions")
+findProject(":markdown:commonmark-extensions")?.name = "commonmark-extensions"