Revamp how addons work

- Addons now nest, which means that addons can manage addons. This has a number
of salutary effects - the scripts addon no longer has to poke into the global
addons list, we no longer have to replace/remove/boot-outof parent addons when
we load scripts, and this paves the way for making our top-level tools into
addons themselves.
- All addon calls are now wrapped in a safe execution environment where
exceptions are caught, and output to stdout/stderr are intercepted and turned
into logs.
- We no longer support script arguments in sys.argv - creating an option
properly is the only way to pass arguments. This means that all scripts are
always directly controllable from interctive tooling, and that arguments are
type-checked.

For now, I've disabled testing of the har dump example - it needs to be moved
to the new argument handling, and become a class addon. I'll address that in a
separate patch.

5 files changed, 25 insertions, 47 deletions

diff --git a/examples/simple/add_header_class.py b/examples/simple/add_header_class.py
index 69b64163..5d5c7902 100644
--- a/examples/simple/add_header_class.py
+++ b/examples/simple/add_header_class.py
@@ -3,5 +3,4 @@ class AddHeader:
         flow.response.headers["newheader"] = "foo"
 
 
-def load(l):
-    return l.boot_into(AddHeader())
+addons = [AddHeader()]
diff --git a/examples/simple/filter_flows.py b/examples/simple/filter_flows.py
index d2b735be..896fa54a 100644
--- a/examples/simple/filter_flows.py
+++ b/examples/simple/filter_flows.py
@@ -17,7 +17,4 @@ class Filter:
             print(flow)
 
 
-def load(l):
-    if len(sys.argv) != 2:
-        raise ValueError("Usage: -s 'filt.py FILTER'")
-    l.boot_into(Filter(sys.argv[1]))
+addons = [Filter(sys.argv[1])]
diff --git a/examples/simple/io_write_dumpfile.py b/examples/simple/io_write_dumpfile.py
index 15e7693c..a0956e33 100644
--- a/examples/simple/io_write_dumpfile.py
+++ b/examples/simple/io_write_dumpfile.py
@@ -23,7 +23,4 @@ class Writer:
             self.w.add(flow)
 
 
-def load(l):
-    if len(sys.argv) != 2:
-        raise ValueError('Usage: -s "flowriter.py filename"')
-    l.boot_into(Writer(sys.argv[1]))
+addons = [Writer(sys.argv[1])]
diff --git a/examples/simple/modify_body_inject_iframe.py b/examples/simple/modify_body_inject_iframe.py
index 442a5118..d54468d2 100644
--- a/examples/simple/modify_body_inject_iframe.py
+++ b/examples/simple/modify_body_inject_iframe.py
@@ -1,29 +1,31 @@
-# Usage: mitmdump -s "iframe_injector.py url"
 # (this script works best with --anticache)
-import sys
 from bs4 import BeautifulSoup
 
 
 class Injector:
-    def __init__(self, iframe_url):
-        self.iframe_url = iframe_url
+    def __init__(self):
+        self.iframe_url = None
+
+    def load(self, loader):
+        loader.add_option(
+            "iframe", str, "", "IFrame to inject"
+        )
+
+    def configure(self, options, updated):
+        self.iframe_url = options.iframe
 
     def response(self, flow):
-        if flow.request.host in self.iframe_url:
-            return
-        html = BeautifulSoup(flow.response.content, "html.parser")
-        if html.body:
-            iframe = html.new_tag(
-                "iframe",
-                src=self.iframe_url,
-                frameborder=0,
-                height=0,
-                width=0)
-            html.body.insert(0, iframe)
-            flow.response.content = str(html).encode("utf8")
+        if self.iframe_url:
+            html = BeautifulSoup(flow.response.content, "html.parser")
+            if html.body:
+                iframe = html.new_tag(
+                    "iframe",
+                    src=self.iframe_url,
+                    frameborder=0,
+                    height=0,
+                    width=0)
+                html.body.insert(0, iframe)
+                flow.response.content = str(html).encode("utf8")
 
 
-def load(l):
-    if len(sys.argv) != 2:
-        raise ValueError('Usage: -s "iframe_injector.py url"')
-    return l.boot_into(Injector(sys.argv[1]))
+addons = [Injector()]
diff --git a/examples/simple/script_arguments.py b/examples/simple/script_arguments.py
deleted file mode 100644
index 84292eb9..00000000
--- a/examples/simple/script_arguments.py
+++ /dev/null
@@ -1,17 +0,0 @@
-import argparse
-
-
-class Replacer:
-    def __init__(self, src, dst):
-        self.src, self.dst = src, dst
-
-    def response(self, flow):
-        flow.response.replace(self.src, self.dst)
-
-
-def load(l):
-    parser = argparse.ArgumentParser()
-    parser.add_argument("src", type=str)
-    parser.add_argument("dst", type=str)
-    args = parser.parse_args()
-    l.boot_into(Replacer(args.src, args.dst))