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Show edit diff before tool execution (fixes #393)

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- Extract diff computation from edit.ts into shared edit-diff.ts
- ToolExecutionComponent computes and caches diff when args are complete
- Diff is visible while permission hooks block, before tool executes
This commit is contained in:
Mario Zechner 2026-01-01 20:34:19 +01:00
parent 173b81bc04
commit 1ed009e2cf
4 changed files with 277 additions and 134 deletions
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203
packages/coding-agent/src/core/tools/edit-diff.ts Normal file
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@ -0,0 +1,203 @@
/**
* Shared diff computation utilities for the edit tool.
* Used by both edit.ts (for execution) and tool-execution.ts (for preview rendering).
*/
import * as Diff from "diff";
import { constants } from "fs";
import { access, readFile } from "fs/promises";
import { resolveToCwd } from "./path-utils.js";
export function detectLineEnding(content: string): "\r\n" | "\n" {
const crlfIdx = content.indexOf("\r\n");
const lfIdx = content.indexOf("\n");
if (lfIdx === -1) return "\n";
if (crlfIdx === -1) return "\n";
return crlfIdx < lfIdx ? "\r\n" : "\n";
}
export function normalizeToLF(text: string): string {
return text.replace(/\r\n/g, "\n").replace(/\r/g, "\n");
}
export function restoreLineEndings(text: string, ending: "\r\n" | "\n"): string {
return ending === "\r\n" ? text.replace(/\n/g, "\r\n") : text;
}
/**
* Generate a unified diff string with line numbers and context.
* Returns both the diff string and the first changed line number (in the new file).
*/
export function generateDiffString(
oldContent: string,
newContent: string,
contextLines = 4,
): { diff: string; firstChangedLine: number | undefined } {
const parts = Diff.diffLines(oldContent, newContent);
const output: string[] = [];
const oldLines = oldContent.split("\n");
const newLines = newContent.split("\n");
const maxLineNum = Math.max(oldLines.length, newLines.length);
const lineNumWidth = String(maxLineNum).length;
let oldLineNum = 1;
let newLineNum = 1;
let lastWasChange = false;
let firstChangedLine: number | undefined;
for (let i = 0; i < parts.length; i++) {
const part = parts[i];
const raw = part.value.split("\n");
if (raw[raw.length - 1] === "") {
raw.pop();
}
if (part.added || part.removed) {
// Capture the first changed line (in the new file)
if (firstChangedLine === undefined) {
firstChangedLine = newLineNum;
}
// Show the change
for (const line of raw) {
if (part.added) {
const lineNum = String(newLineNum).padStart(lineNumWidth, " ");
output.push(`+${lineNum} ${line}`);
newLineNum++;
} else {
// removed
const lineNum = String(oldLineNum).padStart(lineNumWidth, " ");
output.push(`-${lineNum} ${line}`);
oldLineNum++;
}
}
lastWasChange = true;
} else {
// Context lines - only show a few before/after changes
const nextPartIsChange = i < parts.length - 1 && (parts[i + 1].added || parts[i + 1].removed);
if (lastWasChange || nextPartIsChange) {
// Show context
let linesToShow = raw;
let skipStart = 0;
let skipEnd = 0;
if (!lastWasChange) {
// Show only last N lines as leading context
skipStart = Math.max(0, raw.length - contextLines);
linesToShow = raw.slice(skipStart);
}
if (!nextPartIsChange && linesToShow.length > contextLines) {
// Show only first N lines as trailing context
skipEnd = linesToShow.length - contextLines;
linesToShow = linesToShow.slice(0, contextLines);
}
// Add ellipsis if we skipped lines at start
if (skipStart > 0) {
output.push(` ${"".padStart(lineNumWidth, " ")} ...`);
// Update line numbers for the skipped leading context
oldLineNum += skipStart;
newLineNum += skipStart;
}
for (const line of linesToShow) {
const lineNum = String(oldLineNum).padStart(lineNumWidth, " ");
output.push(` ${lineNum} ${line}`);
oldLineNum++;
newLineNum++;
}
// Add ellipsis if we skipped lines at end
if (skipEnd > 0) {
output.push(` ${"".padStart(lineNumWidth, " ")} ...`);
// Update line numbers for the skipped trailing context
oldLineNum += skipEnd;
newLineNum += skipEnd;
}
} else {
// Skip these context lines entirely
oldLineNum += raw.length;
newLineNum += raw.length;
}
lastWasChange = false;
}
}
return { diff: output.join("\n"), firstChangedLine };
}
export interface EditDiffResult {
diff: string;
firstChangedLine: number | undefined;
}
export interface EditDiffError {
error: string;
}
/**
* Compute the diff for an edit operation without applying it.
* Used for preview rendering in the TUI before the tool executes.
*/
export async function computeEditDiff(
path: string,
oldText: string,
newText: string,
cwd: string,
): Promise<EditDiffResult | EditDiffError> {
const absolutePath = resolveToCwd(path, cwd);
try {
// Check if file exists and is readable
try {
await access(absolutePath, constants.R_OK);
} catch {
return { error: `File not found: ${path}` };
}
// Read the file
const content = await readFile(absolutePath, "utf-8");
const normalizedContent = normalizeToLF(content);
const normalizedOldText = normalizeToLF(oldText);
const normalizedNewText = normalizeToLF(newText);
// Check if old text exists
if (!normalizedContent.includes(normalizedOldText)) {
return {
error: `Could not find the exact text in ${path}. The old text must match exactly including all whitespace and newlines.`,
};
}
// Count occurrences
const occurrences = normalizedContent.split(normalizedOldText).length - 1;
if (occurrences > 1) {
return {
error: `Found ${occurrences} occurrences of the text in ${path}. The text must be unique. Please provide more context to make it unique.`,
};
}
// Compute the new content
const index = normalizedContent.indexOf(normalizedOldText);
const normalizedNewContent =
normalizedContent.substring(0, index) +
normalizedNewText +
normalizedContent.substring(index + normalizedOldText.length);
// Check if it would actually change anything
if (normalizedContent === normalizedNewContent) {
return {
error: `No changes would be made to ${path}. The replacement produces identical content.`,
};
}
// Generate the diff
return generateDiffString(normalizedContent, normalizedNewContent);
} catch (err) {
return { error: err instanceof Error ? err.message : String(err) };
}
}

124
packages/coding-agent/src/core/tools/edit.ts
View file

@ -1,132 +1,10 @@
import type { AgentTool } from "@mariozechner/pi-agent-core";
import { Type } from "@sinclair/typebox";
import * as Diff from "diff";
import { constants } from "fs";
import { access, readFile, writeFile } from "fs/promises";
import { detectLineEnding, generateDiffString, normalizeToLF, restoreLineEndings } from "./edit-diff.js";
import { resolveToCwd } from "./path-utils.js";
function detectLineEnding(content: string): "\r\n" | "\n" {
const crlfIdx = content.indexOf("\r\n");
const lfIdx = content.indexOf("\n");
if (lfIdx === -1) return "\n";
if (crlfIdx === -1) return "\n";
return crlfIdx < lfIdx ? "\r\n" : "\n";
}
function normalizeToLF(text: string): string {
return text.replace(/\r\n/g, "\n").replace(/\r/g, "\n");
}
function restoreLineEndings(text: string, ending: "\r\n" | "\n"): string {
return ending === "\r\n" ? text.replace(/\n/g, "\r\n") : text;
}
/**
* Generate a unified diff string with line numbers and context
* Returns both the diff string and the first changed line number (in the new file)
*/
function generateDiffString(
oldContent: string,
newContent: string,
contextLines = 4,
): { diff: string; firstChangedLine: number | undefined } {
const parts = Diff.diffLines(oldContent, newContent);
const output: string[] = [];
const oldLines = oldContent.split("\n");
const newLines = newContent.split("\n");
const maxLineNum = Math.max(oldLines.length, newLines.length);
const lineNumWidth = String(maxLineNum).length;
let oldLineNum = 1;
let newLineNum = 1;
let lastWasChange = false;
let firstChangedLine: number | undefined;
for (let i = 0; i < parts.length; i++) {
const part = parts[i];
const raw = part.value.split("\n");
if (raw[raw.length - 1] === "") {
raw.pop();
}
if (part.added || part.removed) {
// Capture the first changed line (in the new file)
if (firstChangedLine === undefined) {
firstChangedLine = newLineNum;
}
// Show the change
for (const line of raw) {
if (part.added) {
const lineNum = String(newLineNum).padStart(lineNumWidth, " ");
output.push(`+${lineNum} ${line}`);
newLineNum++;
} else {
// removed
const lineNum = String(oldLineNum).padStart(lineNumWidth, " ");
output.push(`-${lineNum} ${line}`);
oldLineNum++;
}
}
lastWasChange = true;
} else {
// Context lines - only show a few before/after changes
const nextPartIsChange = i < parts.length - 1 && (parts[i + 1].added || parts[i + 1].removed);
if (lastWasChange || nextPartIsChange) {
// Show context
let linesToShow = raw;
let skipStart = 0;
let skipEnd = 0;
if (!lastWasChange) {
// Show only last N lines as leading context
skipStart = Math.max(0, raw.length - contextLines);
linesToShow = raw.slice(skipStart);
}
if (!nextPartIsChange && linesToShow.length > contextLines) {
// Show only first N lines as trailing context
skipEnd = linesToShow.length - contextLines;
linesToShow = linesToShow.slice(0, contextLines);
}
// Add ellipsis if we skipped lines at start
if (skipStart > 0) {
output.push(` ${"".padStart(lineNumWidth, " ")} ...`);
// Update line numbers for the skipped leading context
oldLineNum += skipStart;
newLineNum += skipStart;
}
for (const line of linesToShow) {
const lineNum = String(oldLineNum).padStart(lineNumWidth, " ");
output.push(` ${lineNum} ${line}`);
oldLineNum++;
newLineNum++;
}
// Add ellipsis if we skipped lines at end
if (skipEnd > 0) {
output.push(` ${"".padStart(lineNumWidth, " ")} ...`);
// Update line numbers for the skipped trailing context
oldLineNum += skipEnd;
newLineNum += skipEnd;
}
} else {
// Skip these context lines entirely
oldLineNum += raw.length;
newLineNum += raw.length;
}
lastWasChange = false;
}
}
return { diff: output.join("\n"), firstChangedLine };
}
const editSchema = Type.Object({
path: Type.String({ description: "Path to the file to edit (relative or absolute)" }),
oldText: Type.String({ description: "Exact text to find and replace (must match exactly)" }),

79
packages/coding-agent/src/modes/interactive/components/tool-execution.ts
View file

@ -12,6 +12,7 @@ import {
} from "@mariozechner/pi-tui";
import stripAnsi from "strip-ansi";
import type { CustomTool } from "../../../core/custom-tools/types.js";
import { computeEditDiff, type EditDiffError, type EditDiffResult } from "../../../core/tools/edit-diff.js";
import { DEFAULT_MAX_BYTES, DEFAULT_MAX_LINES, formatSize } from "../../../core/tools/truncate.js";
import { sanitizeBinaryOutput } from "../../../utils/shell.js";
import { getLanguageFromPath, highlightCode, theme } from "../theme/theme.js";
@ -58,11 +59,15 @@ export class ToolExecutionComponent extends Container {
private isPartial = true;
private customTool?: CustomTool;
private ui: TUI;
private cwd: string;
private result?: {
content: Array<{ type: string; text?: string; data?: string; mimeType?: string }>;
isError: boolean;
details?: any;
};
// Cached edit diff preview (computed when args arrive, before tool executes)
private editDiffPreview?: EditDiffResult | EditDiffError;
private editDiffArgsKey?: string; // Track which args the preview is for
constructor(
toolName: string,
@ -70,6 +75,7 @@ export class ToolExecutionComponent extends Container {
options: ToolExecutionOptions = {},
customTool: CustomTool | undefined,
ui: TUI,
cwd: string = process.cwd(),
) {
super();
this.toolName = toolName;
@ -77,6 +83,7 @@ export class ToolExecutionComponent extends Container {
this.showImages = options.showImages ?? true;
this.customTool = customTool;
this.ui = ui;
this.cwd = cwd;
this.addChild(new Spacer(1));
@ -98,6 +105,47 @@ export class ToolExecutionComponent extends Container {
this.updateDisplay();
}
/**
* Signal that args are complete (tool is about to execute).
* This triggers diff computation for edit tool.
*/
setArgsComplete(): void {
this.maybeComputeEditDiff();
}
/**
* Compute edit diff preview when we have complete args.
* This runs async and updates display when done.
*/
private maybeComputeEditDiff(): void {
if (this.toolName !== "edit") return;
const path = this.args?.path;
const oldText = this.args?.oldText;
const newText = this.args?.newText;
// Need all three params to compute diff
if (!path || oldText === undefined || newText === undefined) return;
// Create a key to track which args this computation is for
const argsKey = JSON.stringify({ path, oldText, newText });
// Skip if we already computed for these exact args
if (this.editDiffArgsKey === argsKey) return;
this.editDiffArgsKey = argsKey;
// Compute diff async
computeEditDiff(path, oldText, newText, this.cwd).then((result) => {
// Only update if args haven't changed since we started
if (this.editDiffArgsKey === argsKey) {
this.editDiffPreview = result;
this.updateDisplay();
this.ui.requestRender();
}
});
}
updateResult(
result: {
content: Array<{ type: string; text?: string; data?: string; mimeType?: string }>;
@ -415,22 +463,31 @@ export class ToolExecutionComponent extends Container {
const rawPath = this.args?.file_path || this.args?.path || "";
const path = shortenPath(rawPath);
// Build path display, appending :line if we have a successful result with line info
// Build path display, appending :line if we have diff info
let pathDisplay = path ? theme.fg("accent", path) : theme.fg("toolOutput", "...");
if (this.result && !this.result.isError && this.result.details?.firstChangedLine) {
pathDisplay += theme.fg("warning", `:${this.result.details.firstChangedLine}`);
const firstChangedLine =
(this.editDiffPreview && "firstChangedLine" in this.editDiffPreview
? this.editDiffPreview.firstChangedLine
: undefined) ||
(this.result && !this.result.isError ? this.result.details?.firstChangedLine : undefined);
if (firstChangedLine) {
pathDisplay += theme.fg("warning", `:${firstChangedLine}`);
}
text = `${theme.fg("toolTitle", theme.bold("edit"))} ${pathDisplay}`;
if (this.result) {
if (this.result.isError) {
const errorText = this.getTextOutput();
if (errorText) {
text += `\n\n${theme.fg("error", errorText)}`;
}
} else if (this.result.details?.diff) {
text += `\n\n${renderDiff(this.result.details.diff, { filePath: rawPath })}`;
if (this.result?.isError) {
// Show error from result
const errorText = this.getTextOutput();
if (errorText) {
text += `\n\n${theme.fg("error", errorText)}`;
}
} else if (this.editDiffPreview) {
// Use cached diff preview (works both before and after execution)
if ("error" in this.editDiffPreview) {
text += `\n\n${theme.fg("error", this.editDiffPreview.error)}`;
} else if (this.editDiffPreview.diff) {
text += `\n\n${renderDiff(this.editDiffPreview.diff, { filePath: rawPath })}`;
}
}
} else if (this.toolName === "ls") {

5
packages/coding-agent/src/modes/interactive/interactive-mode.ts
View file

@ -902,6 +902,11 @@ export class InteractiveMode {
});
}
this.pendingTools.clear();
} else {
// Args are now complete - trigger diff computation for edit tools
for (const [, component] of this.pendingTools.entries()) {
component.setArgsComplete();
}
}
this.streamingComponent = undefined;
this.streamingMessage = undefined;