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Bug 2078656 - Fix firefox-prefs tools and migrate them to BiDi #202

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Merged
hbenl merged 1 commit into from
Oct 6, 2026
Merged

Bug 2078656 - Fix firefox-prefs tools and migrate them to BiDi #202

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2 changes: 1 addition & 1 deletion src/firefox/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ export class FirefoxClient {
this.core = new FirefoxCore(options);
}

private getBidi(): BiDiFacade {
getBidi(): BiDiFacade {
if (!this.bidi) {
throw new Error('Not connected');
}
Expand Down
271 changes: 105 additions & 166 deletions src/tools/firefox-prefs.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,11 +4,36 @@
* Requires MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1
*/

import type { BrowsingContext } from 'webdriver-bidi-protocol';
import { logError } from '../utils/logger.js';
import { successResponse } from '../utils/response-helpers.js';
import { FirefoxClient } from '../firefox/index.js';
import { generatePrefScript } from '../firefox/pref-utils.js';
import { defineModule, defineToolHandler, type ToolDefinition } from './module.js';
import type { McpToolResponse } from '../types/common.js';

async function getPrivilegedContext(firefox: FirefoxClient) {
let contexts: BrowsingContext.InfoList = [];
try {
// Get privileged ("chrome") contexts
const result = await firefox.sendBiDiCommand('browsingContext.getTree', {
'moz:scope': 'chrome',
maxDepth: 1,
});
contexts = result.contexts || [];
} catch (error) {
logError('Failed to get privileged contexts', error);
}

if (contexts.length === 0) {
throw new Error(
'No privileged contexts available. Ensure MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1 is set.'
);
}

return contexts[0]!.context;
}

// ============================================================================
// Tool: set_firefox_prefs
// ============================================================================
Expand Down Expand Up @@ -38,88 +63,45 @@ export const setFirefoxPrefsTool = {

export const handleSetFirefoxPrefs = defineToolHandler(
async (args: unknown): Promise<McpToolResponse> => {
try {
const { prefs } = args as { prefs: Record<string, string | number | boolean> };

if (!prefs || typeof prefs !== 'object') {
throw new Error('prefs parameter is required and must be an object');
}
const { prefs } = args as { prefs: Record<string, string | number | boolean> };

const prefEntries = Object.entries(prefs);
if (prefEntries.length === 0) {
return successResponse('No preferences to set');
}

const { getFirefox } = await import('../index.js');
const firefox = await getFirefox();

// Get privileged ("chrome") contexts
const result = await firefox.sendBiDiCommand('browsingContext.getTree', {
'moz:scope': 'chrome',
});

const contexts = result.contexts || [];
if (contexts.length === 0) {
throw new Error(
'No privileged contexts available. Ensure MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1 is set.'
);
}
if (!prefs || typeof prefs !== 'object') {
throw new Error('prefs parameter is required and must be an object');
}

const driver = firefox.getDriver();
const chromeContextId = contexts[0]!.context;
const prefEntries = Object.entries(prefs);
if (prefEntries.length === 0) {
return successResponse('No preferences to set');
}

// Remember current context
const originalContextId = firefox.getCurrentContextId();
const { getFirefox } = await import('../index.js');
const firefox = await getFirefox();
const chromeContextId = await getPrivilegedContext(firefox);
const results: string[] = [];
const errors: string[] = [];

// Set each preference
for (const [name, value] of prefEntries) {
try {
// Switch to chrome context
await driver.switchTo().window(chromeContextId);
await driver.setContext('chrome');

const results: string[] = [];
const errors: string[] = [];

// Set each preference
for (const [name, value] of prefEntries) {
try {
const script = generatePrefScript(name, value);
await driver.executeScript(script);
results.push(` ${name} = ${JSON.stringify(value)}`);
} catch (error) {
errors.push(` ${name}: ${error instanceof Error ? error.message : String(error)}`);
}
}

const output: string[] = [];
if (results.length > 0) {
output.push(`Set ${results.length} preference(s):`);
output.push(...results);
}
if (errors.length > 0) {
output.push(`\nFailed to set ${errors.length} preference(s):`);
output.push(...errors);
}

return successResponse(output.join('\n'));
} finally {
// Restore previous context (skip if already on the right chrome context)
try {
if (originalContextId && originalContextId !== chromeContextId) {
await driver.setContext('content');
await driver.switchTo().window(originalContextId);
}
} catch {
// Ignore errors restoring context
}
}
} catch (error) {
if (error instanceof Error && error.message.includes('UnsupportedOperationError')) {
throw new Error(
'Chrome context access not enabled. Set MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1 environment variable and restart Firefox.'
);
const script = generatePrefScript(name, value);
await firefox.getBidi().evaluate(chromeContextId, script);
results.push(` ${name} = ${JSON.stringify(value)}`);
} catch (error) {
errors.push(` ${name}: ${error instanceof Error ? error.message : String(error)}`);
}
throw error;
}

const output: string[] = [];
if (results.length > 0) {
output.push(`Set ${results.length} preference(s):`);
output.push(...results);
}
if (errors.length > 0) {
output.push(`\nFailed to set ${errors.length} preference(s):`);
output.push(...errors);
}

return successResponse(output.join('\n'));
}
);

Expand Down Expand Up @@ -149,105 +131,62 @@ export const getFirefoxPrefsTool = {

export const handleGetFirefoxPrefs = defineToolHandler(
async (args: unknown): Promise<McpToolResponse> => {
try {
const { names } = args as { names: string[] };

if (!names || !Array.isArray(names) || names.length === 0) {
throw new Error('names parameter is required and must be a non-empty array');
}

const { getFirefox } = await import('../index.js');
const firefox = await getFirefox();
const { names } = args as { names: string[] };

// Get privileged ("chrome") contexts
const result = await firefox.sendBiDiCommand('browsingContext.getTree', {
'moz:scope': 'chrome',
});

const contexts = result.contexts || [];
if (contexts.length === 0) {
throw new Error(
'No privileged contexts available. Ensure MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1 is set.'
);
}

const driver = firefox.getDriver();
const chromeContextId = contexts[0]!.context;
if (!names || !Array.isArray(names) || names.length === 0) {
throw new Error('names parameter is required and must be a non-empty array');
}

// Remember current context
const originalContextId = firefox.getCurrentContextId();
const { getFirefox } = await import('../index.js');
const firefox = await getFirefox();
const chromeContextId = await getPrivilegedContext(firefox);
const results: string[] = [];
const errors: string[] = [];

// Read each preference
for (const name of names) {
try {
// Switch to chrome context
await driver.switchTo().window(chromeContextId);
await driver.setContext('chrome');

const results: string[] = [];
const errors: string[] = [];

// Read each preference
for (const name of names) {
try {
// Use getPrefType to determine how to read the pref
const script = `
(function() {
const type = Services.prefs.getPrefType(${JSON.stringify(name)});
if (type === Services.prefs.PREF_INVALID) {
return { exists: false };
} else if (type === Services.prefs.PREF_BOOL) {
return { exists: true, value: Services.prefs.getBoolPref(${JSON.stringify(name)}) };
} else if (type === Services.prefs.PREF_INT) {
return { exists: true, value: Services.prefs.getIntPref(${JSON.stringify(name)}) };
} else {
return { exists: true, value: Services.prefs.getStringPref(${JSON.stringify(name)}) };
}
})()
`;
const prefResult = (await driver.executeScript(`return ${script}`)) as {
exists: boolean;
value?: unknown;
};

if (prefResult.exists) {
results.push(` ${name} = ${JSON.stringify(prefResult.value)}`);
} else {
results.push(` ${name} = (not set)`);
}
} catch (error) {
errors.push(` ${name}: ${error instanceof Error ? error.message : String(error)}`);
}
}

const output: string[] = [];
if (results.length > 0) {
output.push(`Firefox Preferences:`);
output.push(...results);
}
if (errors.length > 0) {
output.push(`\nFailed to read ${errors.length} preference(s):`);
output.push(...errors);
}

return successResponse(output.join('\n'));
} finally {
// Restore previous context (skip if already on the right chrome context)
try {
if (originalContextId && originalContextId !== chromeContextId) {
await driver.setContext('content');
await driver.switchTo().window(originalContextId);
// Use getPrefType to determine how to read the pref
const script = `
(function() {
const type = Services.prefs.getPrefType(${JSON.stringify(name)});
if (type === Services.prefs.PREF_INVALID) {
return { exists: false };
} else if (type === Services.prefs.PREF_BOOL) {
return { exists: true, value: Services.prefs.getBoolPref(${JSON.stringify(name)}) };
} else if (type === Services.prefs.PREF_INT) {
return { exists: true, value: Services.prefs.getIntPref(${JSON.stringify(name)}) };
} else {
return { exists: true, value: Services.prefs.getStringPref(${JSON.stringify(name)}) };
}
} catch {
// Ignore errors restoring context
})()
`;
const prefResult = await firefox.getBidi().evaluate<{
exists: boolean;
value?: unknown;
}>(chromeContextId, script);

if (prefResult.exists) {
results.push(` ${name} = ${JSON.stringify(prefResult.value)}`);
} else {
results.push(` ${name} = (not set)`);
}
} catch (error) {
errors.push(` ${name}: ${error instanceof Error ? error.message : String(error)}`);
}
} catch (error) {
if (error instanceof Error && error.message.includes('UnsupportedOperationError')) {
throw new Error(
'Chrome context access not enabled. Set MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1 environment variable and restart Firefox.'
);
}
throw error;
}

const output: string[] = [];
if (results.length > 0) {
output.push(`Firefox Preferences:`);
output.push(...results);
}
if (errors.length > 0) {
output.push(`\nFailed to read ${errors.length} preference(s):`);
output.push(...errors);
}

return successResponse(output.join('\n'));
}
);

Expand Down
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