Highlight ranges in source description

5 files changed, 92 insertions, 16 deletions

diff --git a/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java b/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
index fe0c6271..0fc05672 100644
--- a/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
+++ b/src/main/java/org/shedlang/compiler/sources/FileFragmentSource.java
@@ -22,7 +22,10 @@ public record FileFragmentSource(
                 return context(
                     line,
                     lineIndex,
-                    characterIndexStart - position
+                    characterIndexStart - position,
+                    nextLinePosition <= characterIndexEnd
+                        ? 1
+                        : Math.max(characterIndexEnd - characterIndexStart, 1)
                 );
             }
             position = nextLinePosition;
@@ -64,9 +67,9 @@ public record FileFragmentSource(
         return at(length, length);
     }
 
-    private String context(String line, int lineIndex, int columnIndex) {
+    private String context(String line, int lineIndex, int columnIndex, int length) {
         var lineNumber = lineIndex + 1;
         var columnNumber = columnIndex + 1;
-        return filename + ":" + lineNumber + ":" + columnNumber + "\n" + line + "\n" + " ".repeat(columnIndex) + "^";
+        return filename + ":" + lineNumber + ":" + columnNumber + "\n" + line + "\n" + " ".repeat(columnIndex) + "^".repeat(length);
     }
 }
diff --git a/src/test/java/org/shedlang/compiler/config/BinConfigTests.java b/src/test/java/org/shedlang/compiler/config/BinConfigTests.java
index d909bb84..eb6514d1 100644
--- a/src/test/java/org/shedlang/compiler/config/BinConfigTests.java
+++ b/src/test/java/org/shedlang/compiler/config/BinConfigTests.java
@@ -52,6 +52,6 @@ public class BinConfigTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:3:20
                 mainNamespace: "A.B",
-                               ^"""));
+                               ^^^^^"""));
     }
 }
diff --git a/src/test/java/org/shedlang/compiler/config/ProjectConfigTests.java b/src/test/java/org/shedlang/compiler/config/ProjectConfigTests.java
index f0deac1e..e710dcc6 100644
--- a/src/test/java/org/shedlang/compiler/config/ProjectConfigTests.java
+++ b/src/test/java/org/shedlang/compiler/config/ProjectConfigTests.java
@@ -95,7 +95,7 @@ public class ProjectConfigTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:1:8
             {bins: true}
-                   ^"""
+                   ^^^^"""
         ));
     }
 
@@ -161,7 +161,7 @@ public class ProjectConfigTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:1:12
             {examples: true}
-                       ^"""
+                       ^^^^"""
         ));
     }
 
@@ -227,7 +227,7 @@ public class ProjectConfigTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:1:12
             {profiles: true}
-                       ^"""
+                       ^^^^"""
         ));
     }
 
diff --git a/src/test/java/org/shedlang/compiler/config/json/Json5ObjectWithSourceTests.java b/src/test/java/org/shedlang/compiler/config/json/Json5ObjectWithSourceTests.java
index ad7f7c1c..4dc1a117 100644
--- a/src/test/java/org/shedlang/compiler/config/json/Json5ObjectWithSourceTests.java
+++ b/src/test/java/org/shedlang/compiler/config/json/Json5ObjectWithSourceTests.java
@@ -41,7 +41,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:13
                         {},
-                        ^"""
+                        ^^"""
         ));
     }
 
@@ -74,7 +74,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:17
                         {x: true},
-                            ^"""
+                            ^^^^"""
         ));
     }
 
@@ -107,7 +107,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:17
                         {x: 1.2},
-                            ^"""
+                            ^^^"""
         ));
     }
 
@@ -189,7 +189,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:17
                         {x: true},
-                            ^"""
+                            ^^^^"""
         ));
     }
 
@@ -247,7 +247,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:13
                         {},
-                        ^"""
+                        ^^"""
         ));
     }
 
@@ -280,7 +280,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:20
                         {name: true},
-                               ^"""
+                               ^^^^"""
         ));
     }
 
@@ -311,7 +311,7 @@ public class Json5ObjectWithSourceTests {
             """
             <string>:5:20
                         {name: "two"},
-                               ^"""
+                               ^^^^^"""
         ));
     }
 
@@ -369,7 +369,7 @@ public class Json5ObjectWithSourceTests {
         assertThat(error.source().describe(), equalTo("""
             <string>:5:20
                         {name: true},
-                               ^"""
+                               ^^^^"""
         ));
     }
 
@@ -400,7 +400,7 @@ public class Json5ObjectWithSourceTests {
             """
             <string>:5:20
                         {name: "two"},
-                               ^"""
+                               ^^^^^"""
         ));
     }
 }
diff --git a/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java b/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java
index c0d7684a..0c1df6ac 100644
--- a/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java
+++ b/src/test/java/org/shedlang/compiler/sources/FileFragmentSourceTests.java
@@ -111,6 +111,79 @@ public class FileFragmentSourceTests {
     }
 
     @Test
+    public void whenSourceIsZeroLengthThenPointerPointsToNextCharacter() {
+        var source = new FileFragmentSource(
+            "<filename>",
+            """
+                abcdef
+                ghijkl
+                mnopqr""",
+            9,
+            9
+        );
+
+        assertThat(source.describe(), equalTo("""
+            <filename>:2:3
+            ghijkl
+              ^"""));
+    }
+
+    @Test
+    public void whenSourceIsOneCharacterThenPointerPointsToCharacter() {
+        var source = new FileFragmentSource(
+            "<filename>",
+            """
+                abcdef
+                ghijkl
+                mnopqr""",
+            9,
+            9
+        );
+
+        assertThat(source.describe(), equalTo("""
+            <filename>:2:3
+            ghijkl
+              ^"""));
+    }
+
+    @Test
+    public void whenSourceIsMultipleCharactersOnSameLineThenPointerPointsToAllCharacters() {
+        var source = new FileFragmentSource(
+            "<filename>",
+            """
+                abcdef
+                ghijkl
+                mnopqr""",
+            9,
+            12
+        );
+
+        assertThat(source.describe(), equalTo("""
+            <filename>:2:3
+            ghijkl
+              ^^^"""));
+    }
+
+    @Test
+    public void whenSourceIsMultipleCharactersOnMultipleLinesThenPointerPointsToFirstCharacter() {
+        // TODO: show multiple lines
+        var source = new FileFragmentSource(
+            "<filename>",
+            """
+                abcdef
+                ghijkl
+                mnopqr""",
+            9,
+            14
+        );
+
+        assertThat(source.describe(), equalTo("""
+            <filename>:2:3
+            ghijkl
+              ^"""));
+    }
+
+    @Test
     public void atReturnsSubsectionOfCompleteSource() {
         var source = FileFragmentSource.file("<filename>", "abcdefg");