[WIP] Improve reliability and detection of JSON objects

.vscodeignore

@@ -10,4 +10,6 @@ vsc-extension-quickstart.md
 **/*.ts
 **/.vscode-test.*
 **/.github
-**/src/test
+**/src/test
+**/*.env
+**/.env*

src/jsonViewer.ts

@@ -1,9 +1,160 @@
 // Generated by Copilot
 import * as vscode from 'vscode';
 
+/**
+ * Checks if a string is likely to be JSON before attempting to parse it
+ * @param str The string to check
+ * @returns An object containing whether the string is likely JSON and a reason if not
+ */
+function isLikelyJson(str: string): { isLikely: boolean, reason?: string } {
+    // Trim the string to remove whitespace
+    str = str.trim();
+
+    // Empty string is not JSON
+    if (!str) {
+        return { isLikely: false, reason: 'Empty string is not valid JSON' };
+    }
+
+    // Check if the string starts with either { or [ which are valid JSON starters
+    if (!(str.startsWith('{') || str.startsWith('['))) {
+        return { isLikely: false, reason: 'JSON must start with { or [' };
+    }
+
+    // Check if the string ends with matching closing bracket/brace
+    if ((str.startsWith('{') && !str.endsWith('}')) || 
+        (str.startsWith('[') && !str.endsWith(']'))) {
+        return { isLikely: false, reason: 'Missing closing bracket/brace' };
+    }
+
+    // Basic check for balanced brackets/braces
+    const stack: string[] = [];
+    const openingBrackets = ['{', '['];
+    const closingBrackets = ['}', ']'];
+    const pairs: {[key: string]: string} = {'}': '{', ']': '['};
+
+    let inString = false;
+    let escapeNext = false;
+
+    for (let i = 0; i < str.length; i++) {
+        const char = str[i];
+
+        // Handle string literals and escaping
+        if (char === '"' && !escapeNext) {
+            inString = !inString;
+        } else if (char === '\\' && inString && !escapeNext) {
+            escapeNext = true;
+            continue;
+        }
+
+        escapeNext = false;
+
+        // Skip characters within string literals
+        if (inString) {
+            continue;
+        }
+
+        // Check for opening brackets
+        if (openingBrackets.includes(char)) {
+            stack.push(char);
+        } 
+        // Check for closing brackets
+        else if (closingBrackets.includes(char)) {
+            if (stack.length === 0 || stack.pop() !== pairs[char]) {
+                return { isLikely: false, reason: 'Unbalanced brackets/braces' };
+            }
+        }
+    }
+
+    // If we finish with unbalanced brackets, it's not valid JSON
+    if (stack.length > 0) {
+        return { isLikely: false, reason: 'Unbalanced brackets/braces' };
+    }
+
+    // Check for common JSON issues like trailing commas
+    if (str.includes(',]') || str.includes(',}')) {
+        return { isLikely: false, reason: 'Trailing commas are not allowed in JSON' };
+    }
+
+    return { isLikely: true };
+}
+
+/**
+ * Attempts to preprocess a string to make it JSON-parseable
+ * @param jsonValue The string to preprocess
+ * @returns The preprocessed string
+ */
+function preprocessJsonString(jsonValue: string): string {
+    // If the value is enclosed in quotes (string representation), remove them
+    if (jsonValue.startsWith('"') && jsonValue.endsWith('"')) {
+        jsonValue = jsonValue.substring(1, jsonValue.length - 1);
+        // Unescape any escaped quotes
+        jsonValue = jsonValue.replace(/\\"/g, '"');
+        // Unescape other common escape sequences
+        jsonValue = jsonValue.replace(/\\([bfnrt])/g, (match, p1) => {
+            const escapeMap: {[key: string]: string} = {
+                'b': '\b', 'f': '\f', 'n': '\n', 'r': '\r', 't': '\t'
+            };
+            return escapeMap[p1] || match;
+        });
+    }
+
+    // Clean up line endings - handle various escaped line endings
+    jsonValue = jsonValue.replace(/\\r\\n|\\n|\\r/g, ' ').trim();
+
+    // Fix common whitespace issues in debugging output
+    jsonValue = jsonValue.replace(/\\t/g, '    ');
+
+    return jsonValue;
+}
+
+/**
+ * Gets a more detailed error message for JSON parsing errors
+ * @param error The error from JSON.parse
+ * @param jsonValue The original string that failed to parse
+ * @param variableName The name of the variable for context
+ * @returns A detailed error message with suggestions
+ */
+function getDetailedJsonErrorMessage(error: Error, jsonValue: string, variableName: string): string {
+    let errorMessage = `"${variableName}" does not appear to be valid JSON`;
+
+    // Extract position from SyntaxError message if available
+    const positionMatch = error.message.match(/position (\d+)/);
+    let position = -1;
+
+    if (positionMatch && positionMatch[1]) {
+        position = parseInt(positionMatch[1], 10);
+    }
+
+    // If we have a position, try to provide more context
+    if (position >= 0) {
+        // Get a snippet of the JSON around the error
+        const start = Math.max(0, position - 10);
+        const end = Math.min(jsonValue.length, position + 10);
+        const snippet = jsonValue.substring(start, end);
+
+        errorMessage += `\n\nError near: ...${snippet}...`;
+
+        // Add a pointer to the exact position
+        const pointerPadding = '...'.length + (position - start);
+        errorMessage += `\n${' '.repeat(pointerPadding)}^`;
+    }
+
+    // Add the original error message
+    errorMessage += `\n\n${error.message}`;
+
+    // Add tips for common JSON errors
+    if (error.message.includes('Unexpected token')) {
+        errorMessage += "\n\nCommon issues: Missing commas between elements, extra commas at end of lists/objects, or unquoted property names.";
+    } else if (error.message.includes('Unexpected end')) {
+        errorMessage += "\n\nCheck for missing closing brackets/braces or incomplete string literals.";
+    }
+
+    return errorMessage;
+}
+
 // Register the viewJson command for debug variables
 export function registerViewJsonCommand(context: vscode.ExtensionContext): void {
-    const viewJsonCommand = vscode.commands.registerCommand('jsondbg.viewJson', async (variable) => {
+    const viewJsonCommand = vscode.commands.registerCommand('jsondbg.viewJson', async (variable: any) => {
         // Get the active debug session
         const session = vscode.debug.activeDebugSession;
         if (!session) {
@@ -40,28 +191,30 @@ export function registerViewJsonCommand(context: vscode.ExtensionContext): void
             } else if (variable && variable.variable && variable.variable.name) {
                 variableName = variable.variable.name;
             }
+
+            // Preprocess the JSON string to improve parsing chances
+            const processedValue = preprocessJsonString(jsonValue);
 
-            // If the value is enclosed in quotes (string representation), remove them
-            if (jsonValue.startsWith('"') && jsonValue.endsWith('"')) {
-                jsonValue = jsonValue.substring(1, jsonValue.length - 1);
-                // Unescape any escaped quotes
-                jsonValue = jsonValue.replace(/\\"/g, '"');
+            // Check if the value is likely JSON before attempting to parse
+            const likelyJson = isLikelyJson(processedValue);
+            if (!likelyJson.isLikely) {
+                vscode.window.showErrorMessage(`"${variableName}" does not appear to be valid JSON: ${likelyJson.reason}`);
+                return;
             }
 
-            // Clean up line endings - handle both \r\n and \n
-            jsonValue = jsonValue.replace(/\\r\\n|\\n|\\r/g, ' ').trim();
-
             try {
                 // Try to parse the JSON string
-                const jsonObj = JSON.parse(jsonValue);
+                const jsonObj = JSON.parse(processedValue);
                 // Create and show the JSON viewer
                 createJsonViewer(jsonObj, context.extensionUri);
             } catch (error) {
-                let errorMessage = `"${variableName}" does not appear to be valid JSON`;
+                // Show a detailed error message
                 if (error instanceof Error) {
-                    errorMessage += `: ${error.message}`;
+                    const detailedError = getDetailedJsonErrorMessage(error, processedValue, variableName);
+                    vscode.window.showErrorMessage(detailedError, { modal: true });
+                } else {
+                    vscode.window.showErrorMessage(`"${variableName}" does not appear to be valid JSON`);
                 }
-                vscode.window.showErrorMessage(errorMessage);
             }
         } catch (error) {
             let errorMessage = 'Error processing variable';

tsconfig.json

@@ -4,7 +4,8 @@
 		"target": "ES2020",
 		"outDir": "out",
 		"lib": [
-			"ES2020"
+			"ES2020",
+			"DOM"
 		],
 		"sourceMap": true,
 		"rootDir": "src",