Continue work on the Stacktrace View.

lib/main.coffee

@@ -11,9 +11,9 @@ module.exports =
     StacktraceView.registerIn(atom.workspace)
 
     atom.on 'stacktrace:accept-trace', ({trace}) =>
-      t = Stacktrace.parse(trace)
-      t.register()
-      atom.workspace.open t.getUrl()
+      for trace in Stacktrace.parse(trace)
+        trace.register()
+        atom.workspace.open trace.getUrl()
 
   deactivate: ->
     atom.off 'stacktrace:accept-trace'

lib/stacktrace-view.coffee

@@ -1,24 +1,53 @@
-{View} = require 'atom'
+{View, EditorView} = require 'atom'
+{Subscriber} = require 'emissary'
+
 {Stacktrace, PREFIX} = require './stacktrace'
 
 class StacktraceView extends View
 
+  Subscriber.includeInto this
+
   @content: (trace) ->
-    @div class: 'stacktrace tool-panel padded', =>
-      @div class: 'header panel', =>
-        @h2 trace.message
+    tclass = if trace.isActive() then 'activated' else ''
+    @div class: "stacktrace tool-panel padded #{tclass}", =>
+      @div class: 'panel padded', =>
+        @h2 class: 'error-message', trace.message
+        @p class: 'activate-control', =>
+          @button class: 'btn btn-primary selected inline-block', click: 'activate', 'Activate'
+          @span class: 'inline-block', 'to navigate around this stacktrace.'
+        @p class: 'deactivate-control', =>
+          @button class: 'btn btn-primary inline-block', click: 'deactivate', 'Deactivate'
+          @span class: 'inline-block', 'to close the stacktrace navigation panel.'
       @div class: 'frames', =>
         for frame in trace.frames
-          @subview 'frame', new FrameView(frame)
+          @subview 'frame', new FrameView frame, => trace.activate()
 
   initialize: (@trace) ->
+    @subscribe Stacktrace, 'active-changed', (e) =>
+      if e.newTrace is @trace
+        @addClass 'activated'
+      else
+        @removeClass 'activated'
+
+  beforeRemove: ->
+    @unsubscribe Stacktrace
 
   # Internal: Return the window title.
+  #
   getTitle: ->
     @trace.message
 
+  # Public: Activate the current {Stacktrace}.
+  #
+  activate: -> @trace.activate()
+
+  # Public: Deactivate the current {Stacktrace}.
+  #
+  deactivate: -> @trace.deactivate()
+
   # Internal: Register an opener function in the workspace to handle URLs
   # generated by a Stacktrace.
+  #
   @registerIn: (workspace) ->
     workspace.registerOpener (filePath) ->
       trace = Stacktrace.forUrl(filePath)
@@ -27,16 +56,35 @@ class StacktraceView extends View
 
 class FrameView extends View
 
-  @content: (frame) ->
+  @content: (frame, navCallback) ->
     @div class: 'frame inset-panel', =>
       @div class: 'panel-heading', =>
+        @span class: 'icon icon-fold inline-block', click: 'minimize'
+        @span class: 'icon icon-unfold inline-block', click: 'restore'
         @span class: 'function-name text-highlight inline-block', frame.functionName
-        @span class: 'source-location text-info inline-block pull-right', =>
-          @text "#{frame.path} @ #{frame.lineNumber}"
-      @div class: 'panel-body padded', =>
-        @pre output: 'source', 'Source goes here'
+        @span class: 'source-location text-info inline-block pull-right', click: 'navigate', =>
+          @text "#{frame.rawPath} @ #{frame.lineNumber}"
+      @div class: 'panel-body padded', outlet: 'body', click: 'navigate', =>
+        @subview 'source', new EditorView(mini: true)
+
+  initialize: (@frame, @navCallback) ->
+    @frame.getContext 3, (err, lines) =>
+      if err?
+        console.error err
+      else
+        @source.getEditor().setText lines.join("\n")
+
+  navigate: ->
+    @navCallback()
+    @frame.navigateTo()
+
+  minimize: ->
+    @addClass 'minimized'
+    @body.hide 'fast'
 
-  initialize: (@frame) ->
+  restore: ->
+    @removeClass 'minimized'
+    @body.show 'fast'
 
 module.exports =
   StacktraceView: StacktraceView

lib/stacktrace.coffee

@@ -1,14 +1,23 @@
+fs = require 'fs'
+
+{Emitter} = require 'emissary'
+
 jsSHA = require 'jssha'
+{chomp} = require 'line-chomper'
 traceParser = null
 
 PREFIX = 'stacktrace://trace'
 
 REGISTRY = {}
+ACTIVE = null
 
 # Internal: A heuristically parsed and interpreted stacktrace.
 #
 class Stacktrace
 
+  # Turn the Stacktrace class into an emitter.
+  Emitter.extend this
+
   constructor: (@frames = [], @message = '') ->
 
   # Internal: Compute the SHA256 checksum of the normalized stacktrace.
@@ -23,6 +32,11 @@ class Stacktrace
   #
   getUrl: -> @url ?= "#{PREFIX}/#{@getChecksum()}"
 
+  # Public: Determine whether or not this Stacktrace is the "active" one. The active Stacktrace is
+  # shown in a bottom navigation panel and highlighted in opened editors.
+  #
+  isActive: -> false
+
   # Internal: Register this trace in a global map by its URL.
   #
   register: ->
@@ -34,6 +48,22 @@ class Stacktrace
   unregister: ->
     delete REGISTRY[@getUrl()]
 
+  # Public: Mark this trace as the "active" one. The active trace is shown in the navigation view
+  # and its frames are given a marker in an open {EditorView}.
+  #
+  activate: ->
+    former = ACTIVE
+    ACTIVE = this
+    if former isnt ACTIVE
+      Stacktrace.emit 'active-changed', oldTrace: former, newTrace: ACTIVE
+
+  # Public: Deactivate this trace if it's active.
+  #
+  deactivate: ->
+    if ACTIVE is this
+      ACTIVE = null
+      Stacktrace.emit 'active-changed', oldTrace: this, newTrace: null
+
   # Public: Parse zero to many Stacktrace instances from a corpus of text.
   #
   # text - A raw blob of text.
@@ -51,11 +81,43 @@ class Stacktrace
   @clearRegistry: ->
     REGISTRY = {}
 
-# Internal: A single stack frame within a {Stacktrace}.
+  # Public: Retrieve the currently activated {Stacktrace}, or null if no trace is active.
+  #
+  @getActivated: -> ACTIVE
+
+# Public: A single stack frame within a {Stacktrace}.
 #
 class Frame
 
-  constructor: (@rawLine, @path, @lineNumber, @functionName) ->
+  constructor: (@rawLine, @rawPath, @lineNumber, @functionName) ->
+    @realPath = @rawPath
+
+  # Public: Asynchronously collect n lines of context around the specified line number in this
+  # frame's source file.
+  #
+  # n        - The number of lines of context to collect on *each* side of the error line. The error
+  #            line will always be `lines[n]` and `lines.length` will be `n * 2 + 1`.
+  # callback - Invoked with any errors or an Array containing the relevant lines.
+  #
+  getContext: (n, callback) ->
+    # Notice that @lineNumber is one-indexed, not zero-indexed.
+    range =
+      fromLine: @lineNumber - n - 1
+      toLine: @lineNumber + n
+      trim: false
+      keepLastEmptyLine: true
+    chomp fs.createReadStream(@realPath), range, callback
+
+  navigateTo: ->
+    position = [@lineNumber - 1, 0]
+    promise = atom.workspace.open @realPath, initialLine: position[0]
+    promise.then (editor) ->
+      editor.setCursorBufferPosition position
+      for ev in atom.workspaceView.getEditorViews()
+        editorView = ev if ev.getEditor() is editor
+      if editorView?
+        editorView.scrollToBufferPosition position, center: true
+
 
 module.exports =
   PREFIX: PREFIX

package.json

@@ -12,6 +12,8 @@
     "atom": ">0.50.0"
   },
   "dependencies": {
-    "jssha": "^1.5.0"
+    "emissary": "^1.2.1",
+    "jssha": "^1.5.0",
+    "line-chomper": "git+https://github.com/smashwilson/line-chomper.git#optional-trim"
   }
 }

spec/fixtures/context.txt

@@ -0,0 +1,10 @@
+one
+two
+three
+  four
+five
+six
+
+eight
+nine
+ten

spec/stacktrace-spec.coffee

@@ -1,4 +1,6 @@
-{Stacktrace} = require '../lib/stacktrace'
+path = require 'path'
+
+{Stacktrace, Frame} = require '../lib/stacktrace'
 {RUBY: {FUNCTION: TRACE}} = require './trace-fixtures'
 
 describe 'Stacktrace', ->
@@ -26,7 +28,7 @@ describe 'Stacktrace', ->
         expect(trace.message).toBe('whoops (RuntimeError)')
 
       it 'parses file paths from each frame', ->
-        filePaths = (frame.path for frame in trace.frames)
+        filePaths = (frame.realPath for frame in trace.frames)
         expected = [
           '/home/smash/samples/tracer/otherdir/file2.rb'
           '/home/smash/samples/tracer/dir/file1.rb'
@@ -72,3 +74,54 @@ describe 'Stacktrace', ->
         expect(Stacktrace.forUrl(trace.getUrl())).toBe(trace)
         trace.unregister()
         expect(Stacktrace.forUrl(trace.getUrl())).toBeUndefined()
+
+    describe 'activation', ->
+      afterEach ->
+        activated = Stacktrace.getActivated()
+        activated.deactivate() if activated?
+        Stacktrace.off 'active-changed'
+
+      it 'can be activated', ->
+        trace.activate()
+        expect(Stacktrace.getActivated()).toBe(trace)
+
+      it 'can be deactivated if activated', ->
+        trace.activate()
+        trace.deactivate()
+        expect(Stacktrace.getActivated()).toBeNull()
+
+      it 'can be deactivated even if not activated', ->
+        trace.deactivate()
+        expect(Stacktrace.getActivated()).toBeNull()
+
+      it 'broadcasts a "active-changed" event', ->
+        event = null
+        Stacktrace.on 'active-changed', (e) -> event = e
+
+        trace.activate()
+        expect(event.oldTrace).toBeNull()
+        expect(event.newTrace).toBe(trace)
+
+describe 'Frame', ->
+  [frame] = []
+
+  beforeEach ->
+    fixturePath = path.join __dirname, 'fixtures', 'context.txt'
+    frame = new Frame('five', fixturePath, 5, 'something')
+
+  it 'acquires n lines of context asynchronously', ->
+    lines = null
+
+    frame.getContext 2, (err, ls) ->
+      throw err if err?
+      lines = ls
+
+    waitsFor -> lines?
+
+    runs ->
+      expect(lines.length).toBe(5)
+      expect(lines[0]).toEqual('three')
+      expect(lines[1]).toEqual('  four')
+      expect(lines[2]).toEqual('five')
+      expect(lines[3]).toEqual('six')
+      expect(lines[4]).toEqual('')

spec/stacktrace-view-spec.coffee

@@ -2,7 +2,7 @@
 {Stacktrace, Frame} = require '../lib/stacktrace'
 
 frames = [
-  new Frame('raw0', 'bottom.rb', 12, 'botfunc', 'Boom')
+  new Frame('raw0', 'bottom.rb', 12, 'botfunc')
   new Frame('raw1', 'middle.rb', 42, 'midfunc')
   new Frame('raw2', 'top.rb', 37, 'topfunc')
 ]
@@ -29,15 +29,31 @@ describe 'StacktraceView', ->
     trace.register()
     expect(opener(trace.getUrl()).trace).toBe(trace)
 
-  it 'shows the error message'
-  it 'renders a subview for each frame'
+  it 'shows the error message', ->
+    text = view.find('.error-message').text()
+    expect(text).toEqual('Boom')
+
+  it 'renders a subview for each frame', ->
+    vs = view.find('.frame')
+    expect(vs.length).toBe(3)
+
+  it 'changes its class when its trace is activated or deactivated', ->
+    Stacktrace.getActivated()?.deactivate()
+    expect(view.hasClass 'activated').toBe(false)
+    trace.activate()
+    expect(view.hasClass 'activated').toBe(true)
 
 describe 'FrameView', ->
   [view] = []
 
   beforeEach ->
-    view = new FrameView(frames[1])
+    view = new FrameView frames[1], ->
+
+  it 'shows the filename and line number', ->
+    text = view.find('.source-location').text()
+    expect(text).toMatch(/middle\.rb/)
+    expect(text).toMatch(/42/)
 
-  it 'shows the filename'
-  it 'shows the line number'
-  it 'shows the function name'
+  it 'shows the function name', ->
+    text = view.find('.function-name').text()
+    expect(text).toEqual('midfunc')

stylesheets/stacktrace.less

@@ -8,4 +8,40 @@
   &.enter-dialog .editor {
     height: 300px;
   }
+
+  .frame .panel-heading {
+    font-size: 130%;
+
+    .source-location:hover {
+      cursor: pointer;
+      text-decoration: underline;
+    }
+  }
+
+  .frame {
+    margin-bottom: 10px;
+
+    .icon-fold, .icon-unfold {
+      cursor: pointer;
+    }
+
+    .icon-unfold { display: none; }
+
+    &.minimized {
+      .icon-unfold { display: inline-block; }
+      .icon-fold { display: none; }
+    }
+
+    .editor {
+      cursor: pointer;
+    }
+  }
+
+  .deactivate-control { display: none; }
+
+  &.activated {
+    .deactivate-control { display: block; }
+    .activate-control { display: none; }
+  }
+
 }